ADDITIVES for CLAYS’ SURFACE FINISHES and PRODUCTS MAKING > Part -II

Post 709 -by Gautam Shah

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Earlier article in the series CLAY MATERIALS for SURFACE FINISHES and PRODUCTS MAKING > Part -I (https://interiordesignassist.wordpress.com/2019/11/02/clay-materials-for-surface-finishes-and-products-making-part-i/)

5 Mixing Hay for Adobe

Clays and soil materials are universally and abundantly available with negligible cost of procurement. Nearly one-half and two-thirds of the world’s population still live or work in buildings made with raw clays, baked into brick walls and floors and use several other baked products like firebricks, storage and cooking utilities like pots and vessels. Variety of mixed soils are used as natural raw materials for structural, building, surface finishes or craft items.

10 Gully Erosion of Soil Dead Sea CoastalErosion

The soils or clay materials display high organic contents as top soil, to nearly mined soils with nearly zero organic component and washed or ground residual products containing mixed organic and mineral substances. Soils have adjustable plasticity, mould-ability, insulating qualities, high thermal capacity, non toxicity, eco friendly nature and simplicity of application. Soils have besides plasticity and shrinkage on drying, issues of deflocculation, coagulation, dry and wet strength of clays.

15 River Silt

Soil colloids are the most active constituent that determines the physical and chemical properties of the soils. These are very small particles which are one-thousandth of a millimetre (0.0001 mm, 0.0004 in). Like other soil particles, some colloids are minerals, whereas others are organic. Mineral colloids are usually refined clay particles. When these particles are mixed with water, they remain suspended indefinitely, turning the water murky. Organic colloids are tiny bits of organic matter that are resistant to decay. Colloidal particles are always in motion because of charge particles. Colloidal particles are transformed from a liquid into a soft semisolid or solid mass by adding an opposite charged ion. Colloidal particles have ability to absorb gases, liquid and solid from their suspension. Colloidal particles never pass through a semipermeable membrane. Colloidal particles have the properties of cohesion and adhesion’.

9 Peat Blocks

Generally, such soils have numerous problems due to the low strength, high compressibility and high level of volumetric changes. Clays need to be improved before these can be used even for soil-based structures like roads, dams, embankments, landfills etc. Improved mix and layering can solve issues of plasticity, swelling, angle of repose, load-bearing behaviour, stability and workability of the clays.

11 Rummu aherainemägi2

Soil Erosion is the displacement of the upper layer of soil, it is one form of soil degradation. Rainfall, and the surface runoff which may result from rainfall, produces four main types of soil erosion: splash erosion, sheet erosion, rill erosion, and gully erosion.

Clay is a fine-grained soil, but not all fine-grained soils are clays. Clays are distinguished from other fine-grained soils by differences in size and mineralogy. Silts are fine-grained soils tend to have larger particle sizes than clays. Mixtures of sand, silt with less than 40% clay are called loam. Loam. Loam makes good soil as a building material.

8 House made of mitti

Clay and Soils are used for forming raw or baked products. Such materials have fewer problems such as shrinkage on drying (cracking), less of homogeneity in dry state, high water permeability -hygroscopic, low weatherability, poor bonding to a substrate -peel off, vulnerability to white ants and insects and colour.

12 38293897802_c842ec3ece_c

Clay products forming processes are, both corrective and additive, unlike wood working, which is basically a deductive process (unless one uses joinery techniques). Clay earthenware processes, at a later stage suffused the stoneware, porcelain and glass making, due to involvement of ‘earthy’ minerals and the heat treatments. In building construction clay products competed against stones, and metals for household items. Stones are not available in all locations and metals need higher technology, compared with the universal material, the Clay.

13 Silt on the banks_of_the_River_Severn_-_geograph.org.uk_-_686914

Plasticity of clay is one its plus quality that is available in no other materials except the flour dough. Clays nominally attain plasticity by addition of moisture, but for high-end ceramics shape forming is through densification by pressure. The plasticity is not a critical criterion, as ceramic soil materials show flow properties at high temperature forming inter-particle bonding.

6 Extruded hollowed Clay blocks being air-dried before going to furnace

Soils are exploited by tackling issues with fillers and additives that are local, low cost and technologically simpler. Fillers and additives are primarily natural materials such as other clays, sands, granules, pozzolana, minerals, crushed baked products (like surkhi, ceramics, coal ash, etc.), dried-rotted agriculture wastes, hairs, natural gums, etc. At the other end, fillers and additives are processed materials like pigments, synthetic fibers, polymeric compounds and resins, oxides, carbonates, Portland cements, calcined lime, etc.

4 Caesarea_Concrete_Bath

Fillers mainly change the physical quality of the soil by adding to the bulk, altering the plasticity and changing the economics profile of raw materials. Additives play an effective role in changing the chemical properties of the mix. Majority of fillers are inferior clays or earth-based products. Additives are proportionately of small volume or weight, like gums, binders, cement, asphalts, pozzolana, lime, bitumen, alkali-acid controllers, colourants (pigments), constituted minerals, baked clay crushing, etc.

14 stacked soil for wall

Fillers and Additives often serve mutually supportive as well as mutually un connected purposes, for one or many of the following reasons.

  1. to improve the quality of basic soil material
  2. to reduce or enhance the moisture content
  3. to control moisture removal
  4. to control plasticity
  5. to achieve a desired colour / texture
  6. to produce specific type of castings / mouldings
  7. to improve weatherability of the final product
  8. to improve upon insect vulnerability
  9. to improve substrate adhesion in wet and dry states.

1 Clay Extracting and mixing water to produce bricks

Clays can take large amounts of water to achieve a fluid, watery mass or pasty form. It can be moulded to any shape, massive, thin wall or with intricate details. The formed clay, when dries out, must still retain the shape and its surface can be modifiable to different finishes, by way of dry engraving, polishing, coating and colouring.

The air-dried forms of clay, on firing becomes permanent and the mass achieves greater soundness. All clay forming processes are energy efficient as use less energy and labour for conversion than the metal shaping-forming processes.

3 Sun dried Adobe Blocks 2815570468_023f24cda7_c

Clay items can be made by poring in, strip or coil stacking, moulding, wet engraving, shaping on a wheel and casting and deductive (carving-engraving) or additive processes. Clay can be liquidized and poured into moulds with very fine details such as hair, costume, drapery or facial features. Such details are difficult with metal castings. Compared to stonework, the finished products of clay are far lighter in weight, and easier to paint. Terracotta products shrink on drying, which is both an asset and drawback. Shrinkage on drying allows easy removal from casting moulds (like bricks, cups, saucers, toilet-wares), but the same in heavy mass items can causes cracking. Clay products on drying have porous mass due to the cavities left out with water evaporation. Such cavities provide light weight mass, greater heat retention, insulation and bonding with joint materials and external surface finish. But for electric and electronics products greater density is achieved by dry mass, greater compaction casting and non plastic raw materials. Clay is considered the most sustainable and eco-friendly material.

Nukus - Khiva, view from Ayaz Qala

Broad classification of Fillers for clays are, 1 Addition of bulk, 2 reinforcement, 3 adjustment of viscosity for shape forming, homogeneity, 4 Bonding, 5 moisture resistance and 6 substrate bonding and workability for surface applications.

Clays have been used from palaeolithic age or earlier. These were earth structures formed, repaired or improvised by dressing, slope forming and shape contouring the lands for forming terrains, flood protection, burial sites, fishing, and water management. These were in the form of embankments, dykes, canals, bridging paths, etc. Various grades of soils and clay were exploited or the purposes of alteration of the angle of repose, drainage, safety from colloidal clay spreads, dousing of bush fires, etc.

2 Soil mixing, raw bricks casting and stacking for drying Image by Bild von Siva Nanthan auf Pixabay

For building of walls, for homes and protection structures clay blocks were cast. For casting viscosity and to prevent cracking on drying reinforcements fillers were required. For both of these purposes’ husks, fine chopped hay, grass and stems, dried leaves, animal excreta, bird droppings, ashes from fires, jute or coir like vegetable fibers, human and animal hair were used. Hay, grass and dry leaves are vulnerable to white ants, but rice-husk due to presence of toxic oils is almost immune from it.

17 Cow Dung Soil mix allowed to mature for few days before using it surface Finish Village women Bangladesh

Cow dung is the most popular filler for clay type of surface finishes, in India. Typically dry season fresh cow dung consists of, 33% solids and 67% of water+gases etc., by weight. The solids in a cow dung are as follows:

  •                   Soluble organic             7.5 parts
  •                  Insoluble organic         76.0 parts
  •                  Soluble inorganic          4.5 parts
  •                  Insoluble inorganic       12.0 parts
  •                  Total                              100.0 parts by weight

A matured or rotted dung is better filler then a fresh one. Rotting and consequent decomposition leaves an odourless mass that does not leach out with the addition of water. Rotting also generates fungicidal and insecticidal agents like gallic acid and tannin. Best way of maturing dung is to mix it thoroughly with 1/3 of all the soil to be used and then allow the slurry to remain in a dark, warm, impermeable pit for at least 72 hours. The clay to cow dung proportion vary according to the type of use such as:

  • Quality of dung           dry of summer or wet of monsoon
  • Type of soil                  organic or mineral
  • Type of plaster            plain, decorative, mural
  • Substrates                    smooth or rough

Dung to clay ratios of 1:4 to 1:8, is common for plaster work, but 1:1 ratio is often used for flooring and art work. Cow dung provides homogeneity, improves workability, retards shrinkage on drying. Clay+cow dung surfaces are fairly impermeable to water.

Dungs of other animals, like horse, donkey and other domestic and wild animals are drier and more fibrous due the quality of diet. For this reason such dungs are more suitable as fillers for excessively plastic clays. But such dungs do not rot or decompose as readily as cow dung.

Scrapping of old Clay+Dung floor and wall surfaces, are added to clay to control the plasticity. Such scrapping from Chulhas and Tandoor are fire baked products, and dust of bricks (Surkhi in India) have cementious siliceous compound. Surkhi is added to clays for floor and wall daubing besides being used for clay tennis court, country cricket pitches, paths and low traffic country roads. Surkhi may need addition or presence of lime in clay to form a cement like compound. Properly rotted, Clay+Dung mixtures have been found to be low-cost eco friendly water seepage resistant base for freshly dug pits and canals.

16 Volcanic Ash Yogyakarta_eruption of Kelud

Pozzolana is volcanic ash. It is an active siliceous material that reacts with hydrated lime to form a gel, which on drying becomes insoluble and stable. Slag is a siliceous waste taken off from the molten ores of metals. If slag is quenched immediately on its removal from a furnace, crystallization of silica into glassy structure is stopped. Slag also needs hydrated lime to harden. Slags however contain sulphur and can be used to neutralize alkaline soils. Surkhi is a manufactured siliceous compound to which addition of lime is not required. These materials are used with organic plastic clays (which tend to be acidic) to achieve initial setting and with mineral soils, for greater homogeneity.

Fly ash, a fine residue of from pulverized burnt coal, collected from chimney stacks and boilers. It contains 55% SiO2, 30% Al2O3, 5% CaO and 7% Fe2O3. These crude forms of tri calcium silicate and tri calcium aluminate in the presence of water bind particles of mineral types of soils. Mineral coal ash, if fine and free from u-burnt coal and sulphur can be used as filler provided black colour is not objectionable.

Portland cement 5% to 18% on dry clay weight basis is used for quick setting, better wear-tear properties and overall mass strength. Sandy or mineral soils require lesser amounts of cement then organic or silt soils.

Additives like, protein glues, vegetable gums and chemical binders are used as binding agents to improve the workability and fast setting. Such additives are of little use with plastic clays but are more suitable for sandy soils. These are water thinnable, hygroscopic and so soften up every time they come into contact with the humidity. But some chemical binders, though is water thinnable, on drying harden into a water insoluble matter. Typical agglutinates are guar gum, arabic gum, casein, soluble starches, cooked starches, molasses, sodium alginate, acrylate and other polymeric resins, amino resins etc. For optimum results the quantity of agglutinate required is small, but their high costs prohibit the use.

Sand stone dust, shell and lime and other kankers provide ‘body’, improve workability and to an extent reduce the shrinkage. Calcined, hydraulic, non hydraulic limes and calcined gypsum (plaster of Paris) are used for better initial setting and overall strength. Whiting and china clay are mainly used to impart lighter colour tones. China-clay, because of its hydrophilic nature helps the mixing of water and `false’-initial setting of the mass.

Other clay fillers include partially ‘digested’ paper-pulps, paper shreds, lint (of cotton seeds), staple fibers, viscose, glass wool, hairs, carding waste of wool and cotton. These mainly reduce the cracking on drying.

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CLAY MATERIALS for SURFACE FINISHES and PRODUCTS MAKING > Part -I

Post 706 -by Gautam Shah

Part -II will deal with ADDITIVES for CLAYS

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Surface finishes and Products composed with CLAY as the prime raw material have been used, for every conceivable purpose and in all parts of the world. Clay is preferred for : Abundant supply, cheapness, universal availability, insulation qualities, ecological value and simplicity of application. Clay finishes and products have some drawbacks like: shrinkage on drying, i.e., cracking, poor weathering qualities, lack of homogeneity in dry state, high water permeability -hygroscopic, poor bonding to a substrate peel-off, vulnerability to white ants and insects.

Kaolin

The quality of the clay-based surface finishes and products depend on:

  1. Quality of soil
  2. Fillers
  3. Additives
  4. Manufacturing processes

OxfordClay_Weymouth

Quality of Soil

Soil is a product, formed mainly from the decomposition of a rock and ashes of lava origin. The decomposed product may remain at its place of origin or get transported to other places by natural forces like water, wind etc. The product, which remains at the place of origin the Residual clays, are comparatively pure, but have less uniform particle size distribution. Materials that after being transported get deposited somewhere else are the Sedimentary or secondary clays. These are generally contaminated by other materials and have smaller but uniform particle size distribution.

Red Iron rich Earth

Principal constituents of clays are Alumina and Silica. Alumina provides the plasticity, and Silica, if free, reduces the shrinkage and warping. Composite silica, though increases the warping on baking. Other elements of clays are Calcium, Magnesium, Iron, Manganese, Potassium and Sodium. Various compositions of these elements and their crystalline structure affect the quality, colour and texture of the soil. Kaolin is the chief constituent of clays used for Ceramics production.

bulldozer-2594001_640

Clays used for products making and surface finishing, are either Top-organic soils or Virgin-non organic soils.

geograph-5983880-by-Philip-Halling

Top-organic soils have substantial amounts of organic matters from the decomposition of vegetation and human, and animals excrete. The presence of organic matters makes a soil light in weight and dark in colour. Organic soils usually show high workability and low shrinkage characteristics. When organic soils are found below an existing layer and are old, contain gallic acid and tannin in small proportions but sufficient to act as fungicide and mild insecticide.

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Virgin or non organic soils have negligible amounts of organic matters, and so reflect the basic characteristic of the predominant constituent element, i.e., lime, silica, or alumina. Non-organic soils, however, do take-on the personality of the other minor minerals present in it. Iron oxide as ferric and ferrous is the most important colourant. Other important colourants are quartz, kaolin, mica etc. Soils show a wide range of colours from off-white to yellow, light brown and chocolate to reddish tones. Non-organic soils unless constituted by colloidal particles show very little plasticity. Some mineral constituents of such soils are reactive to water resulting in swelling and leaching.

640px-Soil_material_containing_Sand,_silt,_clay

Residual or sedimentary materials available at the top of the surface, or below a certain depth, can be classified as: Clays, Sands, Silt, Shale, Colloids, Hard pan, Hoggin, Loam, Peat-Muc, Humus.

Estructura-suelo

Clays are fine albuminous products formed by decomposition of igneous rocks (lava activity). Clays are tenacious and plastic when wet. Clays are highly cohesive, have high capillaries and no internal friction. Clays are smooth to touch, sticky and plastic. Clays can also be classified according to their plasticity, or silt content. Hard clays or stiff clays have low sand content, and are difficult to excavate. Fine clays have medium sand content, and can be excavated with slight effort. Soft clays have coarse texture and are easy to excavate. Pure clays are mostly useless because of the high plasticity and excessive shrinkage on drying. Plastic clays are called fat clays, and less plastic clays and are also called lean clays.

Ball ClaysClays are black, white, red, brown and yellow in colour. China Clay is a residual material, contaminated with silica, mica, feldspar and decomposed feldspar. Ball clay is a sedimentary material of fine grain size and some organic contents. It is finer than china clay. Fire clays are formed from feldspar as residual and sedimentary deposit. Brick clays are high in iron content, and impurities of calcium compounds and organic matter.

Sands

Sands are of small granular particles, usually of stones. Sands are gritty to touch, with little cohesion. It has high internal friction and very little capillarity. Silts are soils that are somewhere between a clay and sand. Silts are slightly gritty to touch and are darker in colour than clays. Colloids are gluey matter found with clays but of ultra fine particles. The colloids absorb moisture and remain suspended, rather than settle down in water. Shale is a compressed and laminated clay with or without organic matter. Shale is plastic when wet but disintegrates when dry.

Volcanic ash deposition

Hard pan is a very dense accumulated mass of soil, consisting of clay, sand, gravel, etc. held together in a rock like but layered formation. Hard pan does not soften when wetting. Hoggin is a natural deposit of a mixture of clay with small stones, grit and sand. Loam is a soft mixed deposit of silty clay and sand in different proportions. Peat-muc and Humus, have fibrous or spongy organic matters formed by the decay of plants. These deposits are black or dark brown in colour, varying compressible in presence-absence of water and so unsuitable for heavy loads. The decomposition of organic material is more advanced in muc than in peat.

digging-in-the-dirt

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RYUKYUAN LACQUERWARE

Post 704  –by Gautam Shah

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This article is compiled from several Internet resources and my own lecture notes on Surface Finishes.

1 Footed Tray with Figures in a Landscape and Symbols of Seven Immortals LACMA

2 Footed Tray

Ryukyuan lacquerware (Ryukyu no Shikki) is the chief craft product of the Ryukyu Islands (Okinawa Prefecture of Japan). Shikki incidentally, stands for lacquerware. Ryukyuan lacquerware represents a unique form and style distinct from the neighbouring places. These have three distinguishing features: the brilliant red colour of the background, gold patterns and use of inlay of mother of pearl. Many items and techniques of making the lacquerware of Ryukyuan, elsewhere in Japan and China are common. ‘Ryukyuan lacquers, yet, are neither purely Chinese nor purely Japanese’. The craft of making or decorating with lacquer is common in many Asian countries.

3 Red lacquer tray with gold engraving Song Dynasty

The art of Lacquerware came to Japan with Buddhism in mid 6th C from China through Korea. When Okinawa was the Ryukyu Kingdom, the lacquer items also came through trade with China during 14th and 15th C. Ryukyuan artisans over the years while exploiting, both the local and imported materials, matured the lacquerware into an ethnic craft by using Ryukyuan motifs.

21 Bowl with cover from Okinawa, 18th C Mother of Pearl Inlay work Wikipedia Image by Hiart Honolulu u_Museum_of_Art

20 Mother of Pearl

4 Lacquer case

Ryukyu, lacquerware have over the years seen several political upheavals, forcing imposition of new styles, but yet the most popular red lacquerware has survived such vagaries. During the 17th and 18th C, following the invasion of Okinawa by Satsuma the Chinese style black lacquerware production was made mandatory. It resulted in mixing up of Ryukyuan and Chinese styles lacquerware in single pieces.

5 Red Lacquer Cabinet with Butterflies

In Ryukyu, lacquerware like cups and bowls were used for offerings in religion rituals, whereas items such as necklaces and decorative utilitarian articles were offered for political gratification. The descendants of Ryukyu samurai and royalty used the lacquerware in formal places in order to forge a connection between people and the Gods. The royal Sho family of the former Ryukyu Kingdom have a set of lacquerware luncheon-basket, leg bowl and wine cups, cherished as the national cultural asset.

6 Chest with Peonies motifs LACMA

Ryukyu lacquerware, over the ages, have seen several modifications. These were, in earlier periods due to the change in patronage by the rulers and also inclusion of new patterns, materials and techniques in the repertoire. In modern times these have been mainly markets driven changes. ‘Chinkin’, the gold inlayed items had traditional vermilion and additional green lacquer. ‘Raden’ the flaked seashells inlayed articles were produced in red lacquer. In later periods Raden pieces were produced with green turban or marine snail shell over black lacquer. From 18th C other techniques were used, such as Hakue (foil lacquering) and Tsuikin (red lacquerware with raised designs). After the annexation of the Ryukyu Kingdom in 1879, Ryukyu lacquerware began to be produced by private workshops and companies.

7 Cosmetic box Kamakura period 13th C plover design in Maki-e Lacquer Tokyo National Museum

4x5 original

Hakue consists of painting a design in lacquer with a makizutsu or a kebo brush and then applying gold leaf or gold-silver powder while the lacquer is half dry. Modern method uses gold, silver, copper, brass, lead, aluminum, platinum, and pewter, as well as their alloys. The Maki-e method was initially used to decorate arms like swords, but adopted over lacquered surfaces.

8 Sutra Box Buddhist with Gold Ming Dynasty

Chinkin (Qiangjin in Chinese) technique is submerging or sinking gold as leaf or powder into carved cinnabar red-lacquered surfaces. This required very fine knife engraving work onto a polished surface. Ryukyu craft-persons preferred a variation of relief building the designs with lacquer putty, called Tsuikin, over the original Chinese method of lacquer (tsuishu) carving. Tsuikin, post 18th C is more common method. Thin sheets of Lacquer mixed with pigments are rolled out. From these various motifs are cut and applied to the craft-item. Due to its easy process, the Tsuikin is very popular process. Hananuri uses the contrast between vermilion and black lacquer. Raden uses seashell flake for inlay work. Mitsudae is a method oil painting (with lead-based pigments) motifs like flowers, birds and skies with white, pink and other bright pastel colours or coloured lacquers (iro-urushie).

10 Modern Vietnam Banana leaf motif in Gold leaf on a red background 1953

In the Heian period (794-1185), when in Japanese history Buddhism, Taoism and other Chinese influences were at their peak, sacred vessels and other articles used by temples of various faiths were of Maki-e style lacquerware. Similarly aristocrats, samurai families, merchants and artisan classes were using Maki-e style items as status symbol and proud possessions.

11 Dish (Pan)With Dragon amid Clouds LACMA

The lacquerware have evolved with many decorating techniques.

Lacquer as a raw material (resinous exudate or secretion of insects flourishing on certain trees), is not local. The material was brought to Okinawa through trade. Exclusive officers were appointed to supervise the production of lacquerware in the Ryukyu Kingdom.

12 Chest with Cartouche Figures on Donkeys in a Landscape Magnolias Plum Blossoms Peonies Birds and Butterflies LACMA

Local woods of Okinawa, such as Deigo coral tree, Sendan or bead tree, Egokoki, Gajumaru, with uniform grains are used.

13 Seal Box with Lotus scrolls & Eight buddhist symbols Red lacquerincised with Gold Qiangjin style

■ Okinawa islands are part of the northern limit of Black sea current which offers the hardest turban shells. Use of wafer-shin shell, prepared by boiling the shell in water for about a week and then pulverizing it (mijingai-nuri) is a local technique. The mix of pulverized shell and lacquer, after applications are rubbed to make a smooth surface (roiro-togidashi).

19 Korean Box, Lacquer inlaid with mother-of-pearl and tortoise shell

15 Gold Lacquer work Tray Japan 19 C

Ryukyu, lacquerware motifs include papaya, plantain, palm trees, hibiscus chrysanthemums, peonies, and other representations of islands’ coastal zone flora. Similarly local and exotic birds and animals, such as long-tailed hens, wagtails (genus Motacilla), chicken, swallows, wagtails, sparrows, mandarin ducks, peacocks and peonies, and a fictional phoenix is found here. Designs that combine and depict flowers and birds are called kachō-zu. Many non local motifs were included to serve the export markets.

Digital Capture

17 Channapatna India Lacquer coated toys

Lacquer coating is common in many parts of the world. Thin lacquer coatings or as applied in multiple layers, nominally do not crack or peel off the surface. Lacquers with additives like wax or oil as plasticizing agents can be applied on many surfaces.

16 Sake Bowls with Lacquer motifs

Shellacs finishes, were the first true clear coatings. Sankheda (Gujarat India) furniture and Chinese lacquer items are examples of shellac coatings. Shellac is a very effective coating material even in very thin viscosity, as a result its penetration and filling capacity is excellent. It is eminently recoatable so a very level and glossy surface is possible. Modern synthetic version NC (nitro-cellulose) lacquer provides a very clear and superior film compared to a shellac and maleic modified resins. Lacquers are modified with alkyds, other synthetic resins and plasticizer so as to control adhesion, softness, toughness and malleability. At fixed levels of viscosities it is possible to formulate lacquers with variable solid contents by varying the degree of molecular linkages. This property renders lacquer as the most versatile coating material for wood, metal, metal foil, leather, fabrics, fibers, plastics, stones, metals, glass, masonry, paper, ceramics, grasses (cane, bamboo), human hair and skin.

Lacquerware from across the world

Links to My other articles

446 COROMANDEL LACQUER

https://designsynopsis.wordpress.com/2019/05/01/446-coromandel-lacquer/

UNDERSTANDING LACQUERS

https://interiordesignassist.wordpress.com/2015/08/16/understanding-lacquers/

LACQUERS or NC LACQUERS

https://interiordesignassist.wordpress.com/2014/04/27/lacquers-or-nc-lacquers/

SHELLAC COATINGS and FRENCH POLISHES

https://interiordesignassist.wordpress.com/2014/04/26/shellac-coatings-and-french-polishes/

LIST of BLOGS on LACQUERS, PAINTS and THINNERS

https://interiordesignassist.wordpress.com/2015/08/17/list-of-blogs-on-lacquers-paints-and-thinners/

 

 

 

WHAT DO WE DO WITH MATERIALS

Post 624 –by Gautam Shah

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We use objects for their many different qualities. Some are used for their structural properties, while others are useful due to their surface qualities. We try to find an object with the best combination of such attributes. Where such a combination is not easily or immediately available, we primarily try to change the object appropriately and secondarily we try to combine materials and create geometric compositions.

640px-aerogel_hand

Aerogel, extremely low density, low thermal conductive material. It is solid and feels like hard styrofoam to touch > Wikipedia image by Image policy

There are Four categories of essential qualities sought in objects for various purposes:

● Engineering Attributes:

Chemical -composition, phase, resistance, structure.

Physical -thermal, electrical, magnetic, gravity-metric, optical, acoustics.

Mechanical -stress/strength, form-ability, rigidity, toughness, durability.

Dimensional Features

Shape -camber, lay/orientation, out of flat, roughness, waviness.

Size -scale, proportion, orientation, nature of perception.

Surface Properties:

Colour -hue, tone, illumination, refractivity, reflectivity, opacity, transparency, fluorescence.

Texture -level and direction of illumination, perceptive organ, nature of contact, scale.

Pattern -random, rational, orientation of cut, original, altered.

Other Considerations:

Availability -local, seasonal, quality, quantity.

Costs  -access, procuring, conversion.

Conveyance  -distance, time, weight, volume.

Handling -safety, storage, containment

Manufacturing -conversion, processing

Spider_silk_cape.jpg

Spider silk Cape from Madagascar golden Orb spider silk > Wikipedia image by Cmglee

For a material to be purposeful two broad considerations are required.

  1.          What one does to a material?
  2.         How the material responds?
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Moulding the earth > Flickr image by Julien Harneis

WHAT ONE DOES TO A MATERIAL ?

We seek an object with a perfect combination of many different qualities. Our quest is however further complicated when we require materials in very large quantities, and of equalized quality. We need materials locally, and often immediately.

512px-laterite_quarry2c_angadipuram2c_india-_c_004

Laterite quarrying for stones at Angadipuram, India > Wikipedia image by Werner Schellmann

HOW THE MATERIAL RESPONDS ?

The material’s response is evident on three counts:

● Other Materials,

● Environment

● User.

● Other Materials: A material responds to other materials within its field. The reaction occurs both, in the presence or absence, of the environment and the user.

A material of a higher phase reacts more readily to a material of the lower phase -, e.g. solid to a liquid. Material with an ion charge reacts to a material with opposite ion charge. A material with lower latent energy becomes recipient.

The response of a material occurs more emphatically, through the surface, than anywhere else. Materials with their own surface systems respond in the same manner as their body would. However, applied surface systems with the same or of foreign materials show different reactions. The surface preparation, application method, and bonding techniques, all play their role in such reactions.

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Doughnut Shop achieving consistent finish > Wikipedia image by Neil T

● Environment: A material-object is affected by many features of the environment. The effects are local if directional (through specific orientation), or occur comprehensively. The constituents of the object also respond differently to specific effects of the environment. For such multilateral environmental demands, single, or mono material systems are inadequate. To serve such demands, separately as well as unitedly, multi-material-objects or composites are conceived. A surface material, covering the entity, forms its own environment for the entity. Here the situation can also be equated to material to environment response.

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Abandoned ship in the former Aral sea, Kazakhstan > Wikipedia image by Staecker

Effects of the environment substantially relate to the movement of earth-sun, and so have a time dimension. The time dimension makes such environmental effects to be temporary, permanent, recurrent, or variable. The effects of environment are structurally causative (capable of causing structural changes in a material), and also sensually attributive (capable of providing the sensorial experiences).

One perhaps cannot terminate the processes of nature, however, the effects of environment can be temporarily delayed or quickened and spatially diffused, or intensified, to programme the functioning of an object.

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Faux rustication > Flickr image by marctasman

● User: A user perceives a material-object in different terms like: Engineering attributes, Dimensional features, Surface properties and for Other considerations. A surface is the most proximate and tangible part of an object. A surface, is often the reason, why an object continues to survive in a particular setting.

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This was part of First chapter – Section 1 of my Notes on Surface Finishes Interior Design Notes

 

PLATES, SHEETS and FILM MATERIALS -part I

Post 580 by Gautam Shah

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Sheets are surface materials with stiff to flexible body. Sheets have high proportion of surface area in comparison to volume. A sheet (mainly metal) is thinner than 6mm when compared to the counterpart, the plate. A film is a thinner formation than a sheet. Sheets, Plates and Films, all have different properties and uses. A sheet is used for packing tins, air-conditioning ducts, automobile bodies, furniture, appliances, utensils, pipes, purlins, etc. A plate is used for heavier structural entities like ships, tunnel sections, pressure storage tanks, chemical reaction vessels, reactors etc. A film is an independent entity applied as a cover or foil, formed by material deposition (gas, liquid or solid), or one integrated to a substrate (surface alloying, surface ceramic formation or molecule deposition).

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Woolaroc Oklahoma Silver Navajo belt buckle of Sheet metal > Wikipedia image by Wolfgang Sauber

Metal sheets are formed chiefly by hot or cold rolling. Polymer, glass, cement, paper, gypsum sheets are extruded or cast. Foams can be classed as cast sheets. Soft sheets such as fabrics, mats etc. are formed by weaving, netting or pressing the mass of fibres. Palm leaves, leathers, skins, timbers, stones, mica, are naturally formed composite sheets.

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Extruded Sheet metal can for beverage > Wikipedia image by http://www.flickr.com/photos/marcodede/116648094/ by Marcos Andre

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Cement cast sheet (board) > Wikipedia image by Swtpc6800 en:userSwtpc6800 Michael Holley

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In modern age substantial volumes of sheets are manufactured by sheet lamination or layering, particulate forming, impregnating woven or non-woven structures, or by sandwiching various types of sheets. A sheet could have skins formed from other or same materials (that constitutes the core). Sheets formed by rolling or extrusion could be in long lengths or small width strips. Sheets, otherwise, are formed and sized to ‘standard’ sizes. The ISO standard sizes (width and length) are in multiples of 300mm. Sheet forms like fabric are manufactured and sized in multiples of 100mm. Paper is supplied in sizes (ISO standard) of series A & B (such as A0, A1, etc.). Standardization of sheet sizes encourages standardization of manufacturing plants, processes, transport, storage and wastage rationalization.

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Embossed Metal floor deck sheets > Pixabay free images by yourschantz

Plates, Sheets and Films, basically have distinctive processing methods, though some may carry common terms. Plates processing, require greater effort to shape, cut or punch through due to their thickness. Plates have characteristic flexural stiffness. So sheets like plywood and other composites behave like plates. Plates may show different stress behaviour on two faces, such as seen in rolling, bending and welding processes. Plates are assembled by welding, rivetting, forging, mechanical joining and occasionally situational fixing. Sheets are processed by methods such as cutting, punching plain bending and deformation bending. Metal sheets formed by cold-forming. Sheets are assembled by butt welding, adhesion joining, seaming, rivetting, screwing and situational fixing (e.g. dove tail joining of wood materials). Film materials in sheet forms are applied by static charging, adhesion or heat melting.

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Expanded sheet metal Lattice > Wikipedia image by Sven Teschke Budingen

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Sheet metal cabinets > Wikipedia image by sailko

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Thin Film material > Wikipedia image by Fieldsken Ken Fields

Malleable metal sheet products are manufactured mainly by stamping or pressing and drawing. Some drawn parts go through changes in body thickness (such as the kitchen pressure cooker forming). Large plastic deformation is an advantageous property for metals’ sheets. During stamping or micro drawing often there are no changes so some processes like corrugation or furniture are done on pre-coated sheets. Stiffer sheets like wood veneers and plywoods, stone (for cladding), acrylics, etc. must be sawn and in few instances shear cut. Sheets show anisotropy or directional variation of mechanical properties where the material reacts differently in different directions. Metal and composites take advantage of this characteristic while creating geometric compositions.

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Corrugated Paper boards Image attribution: Chris 73 / Wikipedia Commons

Sheets are further processed like folding, corrugation, embossing, and perforation to impart geometric qualities. Sheets are engraved or etched by mechanical, laser and plasma-based processes. Simple processes like grinding, rubbing, ironing, burnishing, flame treatments are applied on wood, paper, leather, fabrics and plastics to remove or suppress surface irregularities. Chemical treatments include Linear Plasma-based processes, nitridation, oxidation electroplating, zinc coating, chromate and phosphate treatments, coating, painting, material deposition, surface hardening, surface alloying and cementation. These alter the surfaces for polarity, wettable, electrical conductive, weldable or solderable, corrosion resistant, tarnish proof, chemical resistant, high wear, hardness and remove surface irregularities.

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Storage tanks of Plates > Wikipedia image by Alex Marshall (Clarke Energy)

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EMULSIONS

Post 577 by Gautam Shah

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Chocolate dipped ice cream on wafer cone (Flip 2019)

Egg white, yolk and plant gums have been part of our life since prehistoric times, as thickening and emulsifying agents. Plant gums, like ‘Gum Arabic’ was used as thickening agent (and as a binder) for body paints, pottery colours and as a food emulsifier. Egg yolks and oil do not mix well but slowly whisking it can create a non separating, stable emulsion. This was technique was also used for forming colour pastes for wall paintings. The colours mixed into an emulsion did not drip or run during application. The egg offered substrate binding properties, whereas the oil helped protect the surface.

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Churning cream to make Butter > Wikipedia image by Adam Engelhart from San Fransisco, California, USA

An emulsion is a mixture of two or more immiscible (that would not normally mix) liquids. It contains very small particles (droplets of microscopic or ultra-microscopic size) of one liquid distributed throughout the other. Chemically, these are colloids with liquids as both phases. In an oil-in-water emulsion, such as butter or margarine, the continuous phase is water and the dispersed phase is oil. Opposite to this, the water-in-oil emulsions, the oil is in continuous phase and water is dispersed into it. Butter and margarine, are examples of water-in-oil emulsions. Mayonnaise is an oil-in-water emulsion, stabilized with lecithin obtained from egg yolk. A mix of oil and water when agitated, forms a temporary emulsion, one where liquids separate immediately. But traditionally emulsifiers like gum Arabic, egg yolk, were used to stop the coalescence of oils droplets.

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Mayonnaise whisking > Wikipedia image >source http://.flickr.com/photos/fotoosvanrobin/3277764542/ author FotoosVanRobin from Netherlands

Milk is a common example of an oil-in-water emulsion. Cream and Butter are both material combinations with same substances, but in different proportions. A Cream is oil-in-water emulsion whereas a Butter is water-in-oil emulsion. Their tastes and textures are though very different. Emulsion products include mayonnaise, margarine, hollandaise, icing, fillings, chewing gum, confectionery items, face creams, skin lotions, make-up products, hair dressing products, dyes, tanning compounds, medical formulations, lithography inks, oil bound distempers (*OBD), and plastic or latex paints. Emulsions deliver a liquid product dispersed in a carrier liquid to reduce the cost, disperse the applied material and add body to the formulation.

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Shaving Creams consist of an emulsion of oils, soaps, or surfactants and water> Wikipedia image by Coffeeaddict

Emulsions are formed and maintained by single or combination of processes like: Addition of an emulsifier, Mechanical mixing, Thickening agents and Heat energy. Stable emulsions can be undone by nullifying the effect of the emulsifier through chemical agents, freezing or high temperature heating.

Emulsifiers: An emulsifier makes the emulsion stable. Addition of surface-active agents reduces the interfacial tension between the dispersed and the continuous phases.

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Body Creams and Lotions > Wikipedia image by Gryffindor

Mechanical mixing: Vigorous stirring with or without stirrer blades causes the dispersible phase into finer droplets to form suspension in the continuous phase.

Thickening agents: Such agents increase the viscosity of the continuous phase, which prevents the movement and coalescence of dispersed droplets. Nominally emulsions have higher viscosity then their individual ingredients. Most emulsions are shear-thinning fluids where vigorous stirring can reduce the viscosity.

Heat energy: The viscosity and interfacial tension of the dispersing phase is reduced by heating.

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Ancient manner of Butter making in Canada > Wikipedia image

Transparency and Colour of Emulsions: The size of the droplet of the dispersing phase affects the light reflection, changing its transparency and colour. Emulsions are cloudy or milky in appearance when disperse-phase is of finer droplets. If the droplets are very large, then it is closer to simple dispersion or suspension. Emulsion paints are added with thixotropic agents that lower the viscosity on stirring before application, but on storage gain high viscosity to prevent settling of pigments.

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Micro-emulsions are thermodynamically stable because the dispersed phase is 0.01–0.2 µm in size. Such emulsions have a characteristic transparency as their droplet size is <25% of the wavelength of visible light. Micro emulsions are stable due to the small size of droplets and high proportion of surfactants in the formulations.

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Screen printing Binders are Acrylic emulsions > Wikipedia image

Polymeric emulsions came into commercial use post 1940s. These are prepared with water as the phase, and stabilized with surfactants (molecules that are hydrophilic (water-loving) in one phase and hydrophobic (water-hating) in the other phase). The polymeric emulsions have very high molecular weight, and so when the water phase evaporates polymers coalesce into a tough film. Plastic or Latex paints as known in USA are plastic paints with polymeric emulsion-based formulations. First acrylic emulsion based ‘binders’ were produced for leather and fabric printing, but soon began to be offered as architectural coatings. Plastic paints were formulated at a time (1940s) when solvent-based paints made with alkyd or linseed oils ruled the markets. Oil paints’ were odorous, toxic, and flammable. Early acrylic paints didn’t bond well to ‘oil painted’ surfaces. Acrylic emulsions offered non yellowing, non cracking, environmentally safe, odourless and non-flammable system.

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Plastic Paint

Acrylic Plastic paint application > Flickr image by http://www.charlesandhudson,com

Acrylic emulsion paint formulations are costly to produce in comparison to ‘oil-based’ paints, and other ‘plastic paints’ such as of Vinyl and PVA (polyvinyl acetate) systems. Interior emulsion paints have high vinyl and low acrylic contents. A paint with a high acrylic content will have much better water and stain resistance.

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‘Emulsifying effects’ since prehistoric times, have now developed into science of fluid behaviour and mixing. The term emulsion has become synonymous for liquid-mix systems, and is used to designate solutions, suspensions, or gels.

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STATES of MATTER and COMPOUNDS

Post 573by Gautam Shah

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Materials have three fundamental states of matter, namely Gas, Liquid, and Solid. The state denotes the structural rigidity and resistance to changes of shape or volume. The state or phase of a matter is due to the temperature and pressure. Most substances are solid at low temperatures, liquid at medium temperatures, and gaseous at high temperatures. The state or the changeover of a phase is not always distinct. The temperature at which any given substance changes from solid to liquid is its Melting point, and the temperature at which it changes from liquid to gas is its Boiling point. In the reverse order the Gas to a Liquid transition is known as Condensation, and Liquid to Solid change as Freezing.

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Mixing Oil, Vinegar and Mustard for whipping into emulsion > Wikipedia image by jeffreyw

Solids have molecules held very close to each other, and so maintain the rigid form without any need for a container. Solids formed by slow cooling have constituent atoms, molecules, or ions packed in a regular order and are called crystalline. Solids cooling down very rapidly have no long-range order for the position of the atoms and so have amorphous structure. Solids can be broadly categorized as organic (Such as the wood, paraffin wax, naphthalene and a wide variety of polymers and plastics) versus inorganic (such as metals, alloys, minerals). Solids are formed when definite bonds exist between component atoms and molecules.

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Air entrained coffee of South India > Wikipedia image by Babithajcosta

Liquids are mostly non-compressible fluid, able to conform to the shape of its container but able to retain more or less constant volume irrespective of the pressure.

Gases are compressible fluids able to take the shape of the container by expanding (or compressing) to fill it.

Plasma is the fourth state of matter following solid, liquid, and gas. Plasma is an ionized (electrified) form of gas. It has a collection of charged gaseous particles containing nearly equal numbers of negative and positive ions. Unlike other gases, plasma may self-generate magnetic fields and electric currents, and respond strongly and collectively to electromagnetic forces.

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Plasma cutting machine Wikipedia image by Steve Brown Photography

Compounds are combination of materials in the same or different phases. Compounds can be separated by a chemical reaction. If a compound is uniform, it is called Homogeneous, and nonuniform compounds are called Heterogeneous. Homogenization is a process of distributing one substance, uniformly throughout another (Ice creams, ketch-ups, etc. are homogenized). A mixture is made from molecules of elements and compounds that are simply mixed together, without chemical bonds. Mixtures can be separated using techniques such as filtration, chromatography, evaporation and distillation.

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Salt + water solution > image attribution: Chris 73 / Wikipedia Commons

Solution: Solution is a homogeneous mixture of two or more substances. The substance present in larger quantity is usually called the solvent, and the other substance present in smaller quantity and dissolved is called the solute. The solvent can be either a liquid or a solid and the solute can be either a gas, a liquid, or a solid. Carbonated water is an example of a Gas (carbon dioxide) dissolved in a Liquid (water). Mixtures of gases, such as the atmosphere, are sometimes referred to as solutions as well. Solutions are distinct from colloids and suspensions in that the particles of the solute are of molecular size and are evenly dispersed among the molecules of the solvent. Solutions appear homogeneous under the microscope, and the solute cannot be separated by filtration. Salts, acids, and bases ionize when they are dissolved in water. Certain metals are soluble in one into another, in the liquid state and solidify with the mixture of atoms preserved. If such a mixture can solidify for different proportions of the two metals, they are said to form a Solid solution of metals.

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Compounded materials occur in following forms: (Medium in Phase)

  • Solid in Solid > Alloys
  • Solid in Liquid > suspension, solution, dispersion
  • Solid in Gas > smoke, airborne dust
  • Liquid in Solid > gel
  • Liquid in Liquid > emulsion, mixture
  • Liquid in Gas > fog, aerosols
  • Gas in Solid > solid foams
  • Gas in Liquid > froth, liquid foam, aerated soda
  • Gas in Gas > atmospheric air
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Cutting tools of Alloys > Wikipedia image by Glenn McKechnie

SOLID in SOLID  A solid solution is a solid-state solution of one or more solutes in a solvent. Solid solutions occur in nature as minerals formed under heat and pressure. It is formed when two metals are completely soluble in liquid state. Typically Brass has copper (64 percent) as the solvent atoms and zinc (36 percent) are solute atoms. Such a mixture is considered a solution (rather than a compound) when the crystal structure of the solvent remains unchanged by addition of the solutes, and when the mixture remains in a single homogeneous phase.

SOLID in LIQUID  Salt or Sugar get dissolved in water forming a Solution. Solution like, amalgams (mercury in silver) are uniform throughout and are homogeneous. On the other hand Sand, Rocks, and wood form heterogeneous mixture where each constituent retains its own chemical identity and properties. A suspension is a heterogeneous mixture containing solid particles that are larger than one micrometer for sedimentation. Colloids have finer suspended particles and do not settle. For suspension to occur some excipients or suspending agents or mechanical agitation is required.

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Smog at Brighton UK by Wikipedia image by Richard Rutter

SOLID in GAS: Very small particles (less than 0.002 mm) can float around in air and larger particles (greater than 0.5 mm) roll along closer to the ground. Smoke and airborne dust are solids in gas medium. The process is used to separate particles of different sizes through mechanical cyclonic effect.

LIQUID in SOLID: Gels are dispersion of molecules of a liquid within a solid. The solid is in continuous phase and liquid is a discontinuous phase. Liquid in solids combinations also manifest when excess amounts (than required for equilibrium) of solute are added to a liquid, a condition called super-saturation occurs. Supersaturated solutions are unstable, and may remain in that state for an indefinite period of time if left undisturbed. However, when solid particles are added at this stage, it encourages crystal growth. A sol is a colloidal suspension of very small solid particles in a continuous liquid medium. Sols are quite stable (often due to presence of dispersion agents) like the blood, pigmented ink, cell fluids and paints. Artificial sols may be prepared by dispersion or condensation.

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Hai dressing gel > Wikipedia image by Bangin

LIQUID in LIQUID: Liquids are miscible or immiscible and chemically they are colloids where both phases are liquids. The particle or droplet size is very large, then it is more likely dispersion or suspension, otherwise it is likely to be an emulsion or a solution.

LIQUID + GAS: Liquid in gas creates a visible mass, as the small particles of liquid have greater surface area, detracting the light. Fog is a natural phenomena considered as a low-lying cloud. Aerosols have liquids in the form of solutions, suspensions, emulsions, and semisolid preparations. Aerosols use propellants of two types: Liquefied-gases and compressed-gases.

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Aerosol cans > Wikipedia image by http://streetflies.org/stue

GAS + SOLID: A suspension of liquid droplets or fine solid particles in a gas is called an aerosol or particulate. In the atmosphere these consist of fine dust and soot particles, sea salt, biogenic and volcanogenic sulfates, nitrates, and cloud droplets. Gas entrained, solids create solid-foams, here the volume of gas is large, with thin films of liquid or solid separating the regions of gas. Solid-foams have two forms: Closed cell-foams, the gas is trapped inside pockets of solid material, and in Open-cell foams the gas pockets connect with each other. Open or continuous cell forms of pliable walls are compressible due to freedom for air to move around.

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Aerogel > Wikipedia image from NASA

 GAS + LIQUID Foams and froths are colloidal systems, where the gas form bubbles in a liquid medium. Liquid foams are made long lasting by addition or presence of a stabilizer or surfactant. Proteins (eggs, oils, gums) are used as foaming agents. Carbon dioxide dissolved in water is used in aerated drinks and firefighting systems. Foaming is not always a desirable condition such as in lubricating oils. Typically air releasing agents or conditions reduce the foaming. Aerogel is a synthetic porous ultra-light material (98.2% air) that is derived from a gel by replacing liquid with air. The result is a solid with extremely low density and low thermal conductivity. It is known as frozen smoke, solid smoke, solid air, or blue smoke.

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Liquefied Petroleum gas is a mix of Propane and Butane with a powerful odourant the Ethanol  > Wikipedia image by Krish Dulal

GAS + GAS: Gases have particles with vast separation in comparison to liquids and solids. This separation usually makes a colourless gas invisible, and offers greater scope for mixing. Mixtures of gases, such as the atmosphere, are called solutions. Gas mixtures are used in a brewery for sparging or purging, that is to remove a (harmful) gas, and for blanketing or inerting to fill up the residual volume with a benign mix. Anesthesia and diving gear have gas mixing facilities in addition to adding water vapour.

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PEWTER

Post 541  -by Gautam Shah

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Pewter Teapots

Pewter Mugs

Pewter is a metal alloy with Tin as the chief constituent. Pewter denotes a vast array of alloy-compositions of many different metals in various measures. Pewter metal of the ancient times contained about 70% Tin and 30% Lead. Both were known as distinct metals since 3000 BC. (Tin shows a chemical similarity to the periodic table group-14 element -the lead). Pewter has been preferred material for craft and utility items, mainly due to its low melting temperature, and the fine finish, it offered. Pewter with high lead content, offered a shining but tarnishing black metal that darkened further on aging. Primitive pewter with lead was hazardous for food storage. And as a result the composition pewter has seen many changes, with efforts directed towards eliminating the lead.

 

Pewter Tableware

Pewter Napkin Rings Flickr image by Didriks

Pewter as craft material offered certain advantages such as: low melting point, malleability, ductility, easy workability and highly crystalline silvery-white surface. Pewter can be crafted by cold-working, as it does not cause hardening like other metals, which often requires annealing. Pewter items are usually cast, and then further finished by hammering, turning on a lathe, burnishing, and sometimes engraving. Pewter alloys were rolled into sheets from cast blobs. Such sheets could be shaped, deformed, spun and welded with tin. The presence of tin provides affinity to all embellishing crafts metals like brass, gold, silver, etc.

Detail on a pewter fork handle from Norway, showing three scenes: King Olaf II of Norway, his men, and a Viking ship Wikipedia image by Author Goldenrowley

Pewter Continental Dollar, 1776 (proposed)

Romans used pewter utilities like cups, plates, dishes, etc. and medallions, rings, armlets, etc. But the use diminished due to lead poisoning. Use of tin with natural ‘impurities’ like bismuth, antimony, copper and silver was known but not clearly understood. Pewter utilities never formed cooking vessels as tin and lead had low softening point of temperature, besides an increased health hazard of lead. Pewter, in spite of its easy workability was primarily a utilitarian metal, and less exploited for its ornamental capacity. Pewter work finished like silver, and was passed off as silver. It was used where precious metal items were too expensive and theft prone. In the 11th C poor churches began to use pewter in place of silver items. Lower classes across Europe, were still using it for eating and drinking. Trade guilds in the 12th C in France and elsewhere began to control the constituents of pewter.

Components and products of pewter manufacture Wikipedia image

By 15th C, the Worshipful Company of Pewterers began to standardize pewter. The first, known as ‘fine metal’, with tin and copper, was marked for tableware. The second, known as ‘trifling metal or trifle’, with fine metal and 4% lead, was designated for holloware. The third, known as ‘lay or ley metal’, with 15% of lead, was meant for non food or drink utilities.

Rockport Pewtersmith Wikipedia image

Modern pewter is without any lead, but with about 91% tin, 7.5 % antimony, and 1.5% copper. Alloying materials like antimony and bismuth make it more durable. The surface of modern pewter is bluish white with soft satin to high sheen finish. It resists tarnishing, while retaining its colour and finish. Without any lead, it is safe for food and drinks. Britannia metal consists of tin, antimony, and copper.

Teapot, Britannia metal, Wikipedia image by Author Daderot

Pewter items are cast, moulded, pressure die-cast or shaped. Pewter was fashioned by hammering (workers called Sadware men) or by casting (workers called Hollow-ware men). Pewter wares were earlier cast in metal moulds, but now Silicon, Teflon and rubber moulds are for mass production. Few items are painted, enamelled, gilded, and inlaid or embellished with other metals and materials. Pewter was the chief tableware until the making of porcelain. Pewter items include household goods, (porringer, plates, tea sets, dishes, basins, spoons, measures, flagons, communion cups, teapots, sugar bowls, beer steins, and cream jugs), candlesticks bases, church vessels, snuffboxes, personal adornments, organ pipes dishes, statuettes and figurines, game medals and presentations, aircraft and other models (replica), coins, support or inner structures for gold-silver presentation items.

Pewter manufacturing Wikipedia image

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COPPER – 2 Copper Compounds

Post 479  –by Gautam Shah

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Once distinctive properties of the pure copper nodules were known, no efforts were spared to reestablish the same results. The intention was to derive a copper material easily and locally, similar to the quality of a pure copper nodule. These search resulted in discovery of many copper-containing substances. The substances were realized while processing the raw materials and finishing copper products. It helped realize many ‘copper like’ materials, but with different properties. It was found that copper became more flexible and easy to work with when heated before hammering, a process of annealing. For example, it was known that beating or forging a copper made it little brittle, but stronger for tool making. It was known that some materials could be heated to very high temperatures, in restricted air or closed environment to extract copper metal, a process of ore smelting.

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Copper figure of a bull from the Temple of Ninhursag, Tell al-‘Ubaid, southern Iraq, around 2600 BC. app 600 mm

Egyptians used copper minerals like malachite and azurite for green and blue colouring the murals and also for lip colouring make-up or body colour. Copper Sulphate was used as a mordant in the dyeing to improve colour fastness. It was also used as a topical application for skin deceases and as biocide additive in mural colours. Copper compounds like cupric oxide were used in the ceramics for achieving blue, green or red tints in glasses, glazes and enamels. Chalcopyrite a mixture of pyrite and copper sulfide, is the most common copper ore, and it has been used to extract copper compounds besides the copper metal. Mineral chalcocite, a cuprous sulfide, was used as black powder.

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Chalcocite

Chalcanthite-cured

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Hathor, Egyptian goddess of the sky, music, dance and art, was also the patron of Sinai, the copper sourcing region for the Egyptians. She was often referred to as Lady of Malachite (the copper mineral). Copper is comparatively environment friendly material. But, historically copper ores were with natural Arsenic. The presence arsenic in copper made it a castable metal and strong enough for weapons and sharp edged tools. Osiris, an Egyptian god, often called the Great Green, is portrayed with green skin. Green malachite was a symbol of joy and the land of the blessed dead was described as the ‘field of malachite.’

Green coloured Osiris tomb of Nefertiti

The smelting process for arsenic containing copper produced poisonous fumes. Tin-bronze was a better choice as it was easier to add tin then control the amount of arsenic. But tin was comparatively rare material. Arsenic copper processing was at peak during Roman times, and its traces have been found in ice layers of Arctic regions.

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A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates. To find a native element in nature, it must be relatively non-reactive and there must be some concentration process. Metallic, semimetallic (metalloid), and nonmetallic elements are known in their native state as minerals. Copper is the only metallic element that has a “reddish” color – it’s actually a metallic orange color. Most metallic elements, apart from gold & copper, are silvery-gray colored. Copper tends to form sharp-edged, irregular, twisted masses of moderately high density. It is moderately soft, but is extremely difficult to break. It has no cleavage and has a distinctive hackly fracture. Such Copper mineralization occurred during the late Mesoproterozoic, at 1.05 to 1.06 billion years ago.” -from Copper skull from the Precambrian of Michigan, USA. https://www.flickr.com/photos/jsjgeology/16680420874

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STONES -Opportunities of Intervention

Post 329 –by Gautam Shah 

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Stones have naturally variegated constitution and surfaces. These, provide with inexhaustible opportunities to work to many different forms, sizes, and finishes. The qualitative consistency of man-made materials though, poses a great challenge to multifarious nature of stone materials.

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The Opportunities of Intervention for stones are of following types:

  1. Stones alone
  2. Stones with other earth-based materials
  3. Stones with natural organic materials: such as plants
  4. Stones with man-made materials such as Ceramics, Metals, Polymers (plastics and elastomers)

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1 STONES ALONE

Stones represent, one of the largest resource of earth-based materials. We have not touched even a small fraction of its top layer of mass. Ecologically its use or disposals are manageable. Only problems with stones supply are its inconsistency of sensorial and other surface qualities, and difficult to predict structural properties. This is where man-made materials prove to be superior and reliable. Man-made materials require complex and costly processing whereas stones as a natural resource though unlimited in supplies have high costs of extraction and transportation. Man-made materials are highly custom created and so are not reused extensively, but stones have nine lives and can be used till conversion to form of a dust particle. Man-made materials are produced through multiple-processing, making them difficult to recycle or dispose off safely.

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2 STONES WITH OTHER EARTH-BASED MATERIALS

Stones combined with other earth-based materials provide many opportunities of usage. However, stones by themselves or with other earth-based materials have limited scope for combinations. These are mainly by positioning such as spreading, layering or stacking with gravity, by using electromagnetic forces or by kinetic method of tying-knotting. Few earth-based cementing materials such as mud, pozolana or plant gums are insufficient in supplies and technically inadequate. Yet use of natural materials with very small proportion of man-made of joining materials and technologies can achieve outstanding results.

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3 STONES WITH NATURAL ORGANIC MATERIALS

Use of organic materials such as plant-based resources (Jungle, Farm produce) has not been explored adequately. Primitive man started using wood in combination of stone, which has been extended to buildings. Its use is limited, as wood is a scarce resource (not easy to replenish). Other organic products require several levels of processing before qualifying their application with stones. Every single new application is worth its wait and expense.

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4 STONES WITH MAN-MADE MATERIALS

Stones have been used with man-made materials like metals etc. But most technologies involve non-mixing combinations, such as mechanical joining, adhesion fixing or coating. Stones and earth-based materials have been used in many synthesizing processes. Stones in their physical form and characteristics have been exploited, as fillers, for creation of composites. However, stones have been less frequently synthesized with man-made materials such as ceramics, metals and polymers. These are going to be the opportunities for the next generation.

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The inspiration derives from the successes achieved in combining Ceramics with Metals. Ceramics and metals individually have diverse temperature of forming. At a temperature a ceramic begins to evolve some metal either evaporate, liquidize or form oxides. A combination seemingly impossible is now being achieved, for example in electrical transmission equipments, electronic components, tools and cutting edges making. Similarly stones can be combined with many other materials.

Metal application technologies provide exciting results here. Metalizing a stone surface with metallic particulate or molecules, by plating and sputtering techniques is not farfetched. Synthetics are mainly made with organic (carbon-based) monomers in polymers but chaining. These have been used both as the matrix and fillers components in composites. And can we visualize stones, not in the role of filler, but of a matrix in composite forming.

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