CARBON and STEELS

CARBON and STEELS

Post 365 ⇒   by Gautam Shah 

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Iron as a metal is very ancient material. It was difficult to process (smelt), unlike materials with lower melting temperatures, such as copper and its alloys. Iron is rarely obtainable in pure form. The impurities in iron derive from the ore, and carbon through the smelting process. Carbon is one of the most important of impurities, varying between 0.002% and 2.1%. Presence of Carbon makes the Iron up to 1000 times a harder material. Technically more than 90 per cent of all steels are carbon steels. Presence of small amounts of carbon changes the quality of steel. It affects strength, hardness, mechanical properties (machining, forming, etc.). With very high percentage of carbon workability and impact strength are reduced, whereas with lower carbon content hardness and tensile strength are higher.

Iron of meteorite -similar to Earth’s inner core

Iron ore pellets

Crude iron or Pig iron metal is produced in a furnace, by mixing ore with coke. The high carbon content of crude iron can be further reduced by refining it with air or oxygen, to turn it into steel. A carbon content metal is commonly called Cast Iron. The carbon content of cast iron is 2.1 percent or more. Gray cast iron is relatively soft. It can be easily machined and welded. It is used for engine cylinder blocks, pipe, and machine tool structures. White cast iron is hard, brittle, but not weldable. When annealed, it becomes malleable cast iron. Malleable cast iron can be welded and machined. It is ductile material. Ductile cast iron is sometimes called nodular or graphite cast iron. It is ductile malleable and weldable.

Iron Ore

Pig Iron billets

Besides carbon other elements present are, manganese, silicon, copper, nickel, chromium, molybdenum, vanadium, tungsten, tin, niobium, zirconium, and non metals like sulphur, phosphorus. These materials mostly find their way through the scrape that is partly used for steel making or through an intentional quality markup. The additions of these materials take steel to the category of Alloy steel. Such alloying elements are added to gain properties like better strength, hardness, durability, or corrosion resistance. These are often called specialty steels.

Crankshaft casting

Adjusting the carbon content is most common tool to control quality of steel. Other quality determinant is the rate at which the steel is cooled. Steel properties are also modified by heat treatments, mechanical working it at hot or cold temperatures and by adding other alloying elements besides carbon.

Steel with high carbon content is hard and strong, but not ductile enough for common uses. In carbon steels, the higher carbon content lowers the melting point and reduces weldability.

Mild steel bars

Low carbon steel has approximately 0.05% to 0.25% carbon content with other materials like manganese. Mild steel, is also known as plain-carbon steel or low-carbon steel. Its very common form of steel, and its material properties are adequate for many applications. It is ductile and malleable. It has a relatively low tensile strength, but is cheap and amenable to cold forming processes. Its surface hardness can be increased with carburizing. It is used for structural steel.

Steel forging

Medium carbon steel has approximately 0.29% to 0.54% carbon content (with 0.60 to 1.65% manganese content). It shows good wear resistance and used for large parts, forging and car parts.

High carbon steel has approximately 0.55% to 0.95% carbon content (with 0.30 to 0.90% manganese content). It is very strong material and used for springs and high-strength wires.

High end Steel – chef’s knife

Ultra high carbon steel has approximately 2.5–3.0% carbon content. These steels that can be tempered to great hardness and used cutting tools, knives, axles or punches. Steel with a carbon content above 2.14% is considered cast iron.

Clydach Gorge Iron Bridge Cast iron supports

Hardened steel usually refers quenched or quenched and tempered steel. Silver steel or high-carbon bright steel, gets its name from its appearance, due to the high carbon content. Silver steel is used for cutting edges and axle components.

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STUCCO WORK

Post 299 – by Gautam Shah

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Stucco work has been interpreted as architectural plaster work, surface texture rendering, painting technique, ornamentation body and sculpting material. It has been also used as a wet ground for fresco painting and dry gesso surface base for painting. Stucco creates a dull or matt surface, so in recent periods it has been used for Calcimine or Dry Distemper and Oil bound Distemper (OBD)  painting systems.

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Palladio built his projects from bricks plastered with stucco rather then stones clad with marbles like his contemporaries. The ornate capitals for columns were made of terracotta. The pediments and architraves were made of, if wood covered with straw lathing and then stucco. He avoided using, the then popular tapestries, to cover the interior walls and instead applied frescoes.

Style European Art Stucco Rococo Facade Painting

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The varied interpretations across ages and cultures relate to the different techniques, materials and purposes, but all relate to surface rendering system. It is now often used for substantial coating systems that are applied with textural effect, convert into a textured formation, or allow ‘work’ post application. These coating systems are based on polymeric emulsions (or Latex systems, as known in USA).

complex of Sultan Qalawun Cairo

Stucco work has been persistently used for interiors, but more diversely on exterior surfaces. In interiors stucco was a surface forming system over which variety of coatings (such as Fresco, Encaustic, Oil, Acrylic) and mural making (such as glass, ceramics, inlay) techniques were applied. On exterior face it was used as a surface rendering (texture) system like for sculpting decorative motifs, figurines and statuettes, and for formation of applique architectonic elements (such as pilasters, tympanums, pendants, pediments, cornices, column fluting, pillars’ heads and bases).

Iran Stucco

Stucco-work began as a wall coating system, probably to rejuvenate the soot-covered walls (blackened due to oil lamp lighting and indoor fires’). It provided a smooth surface over a variety of wall surfaces such as adobe, reeds, brick and stone. Examples of stucco-work occur in the Aztec architecture of Mexico, Egypt, Sumerian buildings and Greek buildings. Romans erected masonry structures, often with recovered materials from ruins of earlier age buildings. These walls were of random pattern, and required plaster as well as textural renderings. For faster finishing of vast buildings, stucco was ideal system for interior and exterior work. With little craftsmanship it provided ‘sculpted and decorative’ artefacts for middle class to replace marble and other stones.

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Stucco work reached new heights during Baroque period. Renaissance period provided smoother stucco surfaces in buildings to contrast the rusticated stone’s corners of openings. Post Renaissance period saw festoons and medallions of stucco on exterior walls. During Gothic period stucco work applied to wood a lath lattice was used for creating intricate ceiling patterns. Walls had cornices, freezes and panels over wood base. It was also realized that a plain wood wall was darker in colour and was susceptible to fire on the other hand stucco or gypsum-covered walls could be painted by water-based coatings (lime-wash, calcimine, distemper, etc.) and, these were fire resistant.

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The basic ingredient for stucco work has been Lime, with addition of Gypsum and marble dust. Other reinforcing additives were hair, fibres, stone chips, etc. Gypsum was costly material, yet it was used with marble dust for imitation marble finishes called Scagliola. Since industrial revolution Portland Cement is being added, and in last 50 years polymeric binders are included.

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Stucco and Plaster work have overlapping interpretations. Plaster is comparatively planer work, created from Gypsum, Lime or Portland Cement and applied for surface leveling and waterproofing. Stucco can have the same materials but applied for creating designs, patterns and statuettes, on internal and external surfaces. The base surface could be structural elements like slabs, walls, and framed or latticed work. Stucco were once created from slow setting lime or gypsum but nowadays could have chemical and polymer binders. High bodied paint formulations applied with texturing tools are also used.

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WROUGHT IRON LATTICES

Post 226 – by Gautam Shah

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Wrought Iron lattices have been used primarily over windows, doors and other gaps. Latticed structures of wrought iron are used for balconies, as space dividers, church screens, vine climbers, stair railings, estate gates and barricades, frames for furniture items, lintels, beams, brackets, columns and for garden structures like orangeries and pavilions.

Iron forming reflects man’s innovative and craft skills. It has been a very difficult material to work with, as it presents different behaviour in its various forms. Yet, it has been cast, resealed, joined, spliced, chased and engraved. It has been reformatted with hot and cold treatments. Wrought iron has been used for household utilities, tools, vessels, arms, building elements, architectonic entities, decorative items and statuettes. It has replaced wood for its stability, strength and malleability.

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Before the Middle Ages, wrought iron was used primarily for weapons, tools and utilities that only could be made with a metal. Unlike Cast iron, Wrought iron has a lower carbon content. It is stronger, non-brittle, and could be forged to any shape, and join by beating. Literally, Wrought iron means an iron that can be worked, both in hot and cold forms.

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One of the most creative forms of wrought iron manifests in trellis, grills, and other hollowed or pierced-out planner forms. Earlier trellis or grills were formed of wood, bamboos, vines, and cast of copper or bronze, or even of ceramics. These materials were not amenable to plastic shaping. Wrought iron has been used as a plastic material to form variety of trellis, in simple or multi-curved planner forms and also mould sub-elements differently.

The first lattices were functional elements like the protective cover within gaps, and in doors and windows. Simple linear cast or forged elements were inserted in side structures of masonry or wood. These, however, soon became interlacing or entwined entities of bars, hot-forged or riveted forming a grill. Same techniques were used for creating grills for hearths and sieves.

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Wrought Iron lattices began to be used 13 and 14th C windows of mansions and cathedrals requiring high security. Same structures were used as barricades and partitions. The lattices were designed with variegated shaping of bars’ profiles, and in terms of angle and spacing. Hot-forging and cold working methods were used to alter the sections and shapes of the linear elements. Round and square rods and bars were twisted, coiled and beaten into complex foliated forms. Iron pieces were chiselled, chased, riveted, shape forged. Iron plates were also used for plate like tracery elements. Ends, finials and cresting were cast from other materials like brass or bronze and mounted over steel roods. Riveting and hot forging was chief techniques of joint making. Joints, However, were so skillfully concealed that the grill seemed like one cast or formed piece.

Wrought ironwork began to serve other decorative purposes. Famous cathedrals and other public buildings ( Canterbury and Winchester Cathedrals of England and Notre Dame de Paris) have extremely crafty pieces wrought iron works.

21793578980_aed850cf69_cWrought Iron lattice work, began as a rough surface entity, but by end of middle ages, the surfaces were well formed, ground and joints were concealed. Surfaces were often chased, engraved, inlayed with materials. Finials, caps and other elements of brass, copper, bronze and gold were added. Ornaments were forged out as separate parts, and assembled with riveting, or welding. Decorative elements, such as of flowers, leaves, vines, birds, names, and coats of arms, were bunched or heaped to provide a composition language.

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SINGLE MATERIAL OBJECTS

Post 184 – by Gautam Shah

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We endeavour to create Single Material Objects. Objects made of single material, whether natural or man-made, have inherent efficiencies. We try to achieve the state of a single material efficiency by integrating or by synthesizing different components.

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  • A window consists of a structural frame, shutters, glazing system, mosquito-nets, curtains, weather-sheds, etc. It would be ideal if one integrated system, made up of a single material were to serve all the purposes.

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  • Similarly a roof is made of the structural slab, outer side water proofing coat, insulation, and floor finishes, and under side plaster, an acoustic ceiling, etc. It would be very efficient to have one material serving all these functions.Roof – multi layer.

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  • A partition is designed to divide a space in terms of visual privacy, safety, stability, sound proofing, fire proofing, heat insulation, provisions for apertures and services, etc. The partitions as a result consist of a structural system and various layers, each designed for specific need. The partition is further coloured and textured for use requirements. The structural elements, layers and the surface treatments can be replaced by a single material-object system. Composite panels for partitioning, is a first attempt in integrating various sub systems.

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640px-Back_side_of_National_Parliament_of_Bangladesh_20A single material system capable of serving many different purposes is not easy to devise. Such an event takes years of effort. However, human ingenuity out-paces such attempts, by inventing superior but totally a different entity, for the given situation. The superiority of a newly invented entity may not be due to the unitary structure or the multi purposiveness of the material, but for its multiplex system of simpler and lesser number of elements.

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An automobile, a computer or a building, is formed of as many parts, as they consist of different materials. If one can reduce the number of parts, automatically the number of materials used, will come down. If a conscious attempt is made to reduce, the number materials used, then there will be reduction in number of components.

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At any cross section of time, we find a large number of materials systems either are overtly attached to other objects, or are in the process of being integrated with them. It is very desirable that an object system in such a situation, be singular in constitution or at least be effective in that manner. Designers aspire to provide a singular object system in place of a multi-component system. In designers’ world, however, there are very few situations where singular object system can satisfy all the demands in a particular time-space profile. Multi-component surface systems are reality.

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TEXTURES and MATERIALS

Post 162by Gautam Shah

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A surface, is often the reason, why an object is being preferred or rejected for a use, and continues to survive in a particular setting. A user perceives the surface of a material-object in many different conditions. A surface is the most proximate and tangible part of an object. The proximity to a surface defines its visual experience whereas the tangibility refers to the mainly tactile sensorial characteristics. Texture is an important qualitative parameter of a surface definition. Textures are intimately linked to specific objects, and deviation from that is immediately registered.

Texture by Modification

Textures are part of naturally occurring objects. We also fashion new finishes by varying the textural qualities. An object acquires a specific colour ‘tinge’ as the texture affects the angle of reflection of light. The angle of perception also has similar effect. The quality of light (the spectral range) and its brightness affect the perception of texture.

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  • There are more than 20 mathematical parameters applied to surface description, and some of the terms are: roughness, irregular features of wave, height, width, lay, and direction on the surface; camber, deviation from straightness; out of flat, measure of macroscopic deviations from flatness of a surface.

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Structure background wallart, backgrounds textures.

We perceive textures through Two basic manners. Visual textures occur through variations in grades of monochrome or coloured surfaces, aided by the shape, size, direction of objects. Contour variations cause tactile textures. But without going closer to the object we perceive the textures through play of shadows and illumination. At this remote perception the texture is visual happening.

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Surface texture is a roughness that can be quantified by the vertical deviations from its “ideal form”. Surface roughness is a very subjective term what is rough for some context may be perceived to be smoother for other conditions. Surface textures are perceived for their extent. Surface texture is also sensed in terms of its proximity as well as its tangibility. A brick wall may be very rough to touch but a very extensive surface may not be perceived to be so rough.

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Textured surfaces have larger area, so greater reactivity with the environment. Roughness of the surfaces and have higher friction coefficient so susceptible higher wear. Surface irregularities are nucleation nodes for trapping of moisture and promote corrosion. Surface texture allows better adhesion.

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Textures are created by several methods, such as:

  • Removal of material >> Etching, Scraping, Roughening, Filing, Grinding, Engraving, Notching, Sculpting, Machining, Blasting, Shearing, Shaving, Singeing, Spluttering, etc.

Burnishing

  • Addition of material >> Painting, Printing, Dyeing, Metalizing, Material deposition, Plastering, Coating, Nitriding, Carburising, Galvanizing, Gilding, etc.

Diamond Polishing

  • By displacement processes like contraction and expansion >> Brushing, Rubbing, Ironing, Chasing, Repousse, Forming, Hammering, Forging, Beating, Levelling, Rolling, Buffing, Washing, Bleaching, Enamelling, Surface Alloying, Denting, Forming, Re-rolling, Peening, Spinning, Twisting, Weaving, Knitting, etc.

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CEMENT FINISHES – part 2

Post – by Gautam Shah

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Cement mortars are rendered on masonry, concrete and other surfaces. The colour of cement, sand, amount of water, mixing, trowel pressure and rendering technique determine the colour of surfaces.

Cement mortars are mixed at two distinctive stages.

1. In dry state mixing of cement is mixed with other ingredients such as lime, chalk, sand, clay, various sizes and shapes of aggregates. Dry mixing requires continuous agitation till water is added, otherwise heavier ingredients settle down. Dry mixing is much easier, requires less energy then any wetted mass. Dry mixing helps penetration of water and thereby reduces the flocculation (wetting of cement particles due to enveloping air). In fast setting or hardening varieties of cements or due to presence of such additives, mixing of wet-mass becomes very difficult due to the resistance.

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2. Dry state mixed mass is combined with water. Very intensely mixed mortars are air entrained and allow calcination of calcium hydroxide (instead of allowing it to combine with silica alumina compounds for cementing action). Air entrained mass also have lighter colour for a very temporary period, due to formation of bubbles.

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Colour of the wet mixed cement-based mass and of the cured-dried mass are nearly uncertain conditions. There are great many operative variants. Cement mixed mortars are affected (tinged) by the colour of the aggregates. So it is very difficult to produce a perfectly white marble mosaic tile or washed chips plaster, unless only pure white aggregates are used. Cement and aggregate flooring such as IPS – Indian Patent Stone, Red Madras floor and Ironite (cast iron milling waste)are all strongly affected by the colour of the constituents.

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Coloured mortars have pigments of iron oxides (black, red and yellow). Green, blue and other colours (though not sun-fast or long lasting) are achieved by use of chrome pigments. For vertical and ceiling surfaces ziki plaster formed with marble dust containing substantial amounts of fine mica and talc. Similarly pearl glow and smooth surface can be achieved by including sea shell dust. Slow setting and engravable cement mortars require high workability, and are achieved by addition of fully calcined gypsum or lime containing such compounds.

Use of fine sands increases the air entraining effect and reduces the workability. Angular or flaky sands are difficult to use in sand face plasters.

Finishes for Concrete Surfaces

A cement agglomerate like concrete can have a finish depending on several factors, such as:

         Form work surface, joints and continuity, use of a release agent, absorbency of the form work surface and setting or hardening enhancer and retarders used.

2          Concrete mix proportions, ingredients’ colour, size, and texture (lighter toned aggregates and sands produce a light-coloured concrete (Colour of cement is variable not only from plant to plant but often batch to batch). Degree of mixing and air entrainment that occur in the mass. Free limes in water creates a soapy foam which also affects the colour.

3          Insufficient or uneven curing affects the hydration and eventually the colour of the concrete.

         Inadequate vibration causes minor pockets of air bubbles, which affects the texture.

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.Joints and Lining works

Cements Joints or lining is rendered over stone, brick and other masonry blocks. Cement is used as a joint material for masonry work and component assemblies, coating material for masonry and other surfaces, casting materials as conglomerated compounds and bonding material for free particulate.

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Cement joints, from a surface finish point of view are very important elements in exposed masonry faces. The joint is usually of a contrasting colour and of smoother texture, then the main material surface. A raked joint or protruding joint looks much darker than a flushed joint or flat joint.

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Cement composites can be rendered to many types of finishes, patterns and textures. Type of ingredients, particle size, grain distribution, colour, structure, shape; techniques of application (trowel float, sprayed gunited, brush coated, sponge sucked, machine vibrated etc.) and post finish cares (premature wash etching, sand blasting, chipping, etc.) all form the quality of surface finish of cement composites.

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Cement is used in types of composites. One of the cheapest combinations is soil-cement, a combination to produce masonry blocks and temporary (light traffic) pathways. Cement and dry agricultural waste or wood chips are used in production of low-cost insulation boards. Cement is also used in binding wood charcoal, lignite, mineral coke and other combustible waste to produce briquettes or fuel pallets.

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VARNISH

Post –by Gautam Shah

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Varnish is clear coating of resin and solvent that dries-hardens to transparent film. Today, Varnish is a generic term for Clear Coatings that provide a colourless (transparent) and (mostly) a glossy surface.

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Clear Coatings are required for several reasons, such as to show-up the surface grain, colour, pattern, or protect artwork or craft pieces. The surface to be coated may not always be perfect or decent. So some form of Conditioning of the substrate surfaces is needed before application of a clear coating.

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The most common problems with surfaces are like:

    1. uneven colour
    2. unsuitable tone
    3.          uneven grain or pattern
    4.          patchy absorbency
    5.          uneven texture
    6.          bleeding or soluble constituents
    7.          waxy or oily deposits
    8.          alkalinity
    9.          acidity
    10.      .   galvanic sensitivity
    11.          moisture content and transfer

Varnished Wood Chair

The word ‘varnish’ comes from Latin ‘vernix’, meaning an odorous resin, Varnish as word comes from Greek ‘Berenice’, which was the ancient name of modern Benghazi in Libya. Perhaps the first varnishes were produced from resins of local trees of Benghazi.

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Varnishes are clear coatings usually made with oils, oleo-resinous substances and alkyds. Varnishes are comparatively slow drying, high bodied finishes and so can be applied by brush, unlike Lacquer or French polish. Varnish types of finishes have thicker film of high gloss, with better wear and tear resistance.

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Varnishes are convertible coatings (materials, which after application change into different but permanent substance), so are more stable.

In the past varnishes were made by boiling linseed or tung oil with modified rosins. Later varnishes were produced from oils with maleic or phenolic modified resins. Nowadays air drying varnishes (oxidation & polymerization) are produced from long oil alkyds, where as baking varnishes (heat polymerization) are produced from medium or short oil alkyds. Often amino resins such as urea and melamine formaldehyde are added to produce a very tough, hard wearing, solvent insoluble, alkali resistant, non yellowing and non degrading film.

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High temperature baking varnishes though superior in many respects have limited use so far as wood, paper and such other surfaces are concerned. Theoretically any film forming medium (used for manufacturing paints -coloured coatings) can be used as a clear coating material, but certain film peculiarities and clarity restrict their use. High grade clear coatings could be of polyurethane, epoxy, polyester, PVA, materials. Varnishes besides wood, are used on paper, leather, fabrics, copper winding wires, pottery products, polymers, insides of food tin and aluminium cans, glass, electronic circuit boards, toys etc.

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STONES for buildings

Post-by Gautam Shah

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Stones like many other natural materials are abundantly available. Most of the rocks that we are likely to encounter and exploit are within the top 16 kilometres of Earth’s face. This mass is made up of 95% Igneous rocks, and rest consisting of widely spread cover of Sedimentary and Metamorphic rocks.

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We today have greater capacity to search over wider terrains and also reach at sub surface locations. Exploitation of stones as collection from the surface or extraction from various depths is not a major technological problem, but economics of transportation limits its commercial usage.

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There are 3 essential sources of Building Stone Materials:

● Surface collected stones

● Extracted stones: protruding and subterranean mass

● Waste and recycled stones

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The stones occur in many forms and sizes:

1 Large pieces which can be further down sized or cut into smaller units,

2 Units that are used without any other processing,

3 Pieces which are crushed or disintegrated into finer particles,

4 Rejected material from mining and collection processes,

5 Wastes from stone sizing and dressing operations,

6 Debris material recovered from demolition of old buildings and other structures.

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SURFACE STONES

Surface stones from single geographic region show qualitative and size variations of minor nature. Further quality equalization can be done by location-based sourcing, visual selection, grading, separation. Surface collected stones can be further quality equalized through many types of ‘processes’.

● Surface collected materials are naturally formed such as boulders, pebbles, gravel, sands, etc. These are very tough materials and equally weathered on all faces.

● Other surface collected materials are broken by natural disintegrating forces like weather, chemical reactions, land mass movements, internal stresses, etc. These stones may show up with varied weathering on their faces. Such materials are fractured along the plane of shearing force or across the weakest plane, and so show unpredictable structural properties, inconsistent colour and grain structure (texture) on different faces. These stones due to their long exposure are either the toughest remains or the weaker fractures. In the first instance further dressing or downsizing is difficult, and in the second case consistent shaping is not possible.

● Such materials are found spread or located over terrain difficult to access. Collection unless manual involves a large amount of useless mass.

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EXTRACTED STONES

Extracted materials are buried (loaded) under the same or different nature of materials’ mass. The over burdening mass protects, as well as contaminates the deposit. The water leaching through the organic soil burden is nominally acidic and affects the alkaline stone mass. Typically Lime stones when freshly extracted, are not exposed to Carbon Dioxide due to the overburden, and so are soft and porous, but begin to harden on aeration.

● Igneous and metamorphic rocks are not strongly stratified and do not present distinctive layers or strata. Sedimentary rocks are stratified, generally in horizontal layers. However, due to movements in the earth mass inclined and curved formations also occur. Sedimentary rocks show grains intervened by a cementing medium.

● Igneous and metamorphic rocks are often made of many different substances, some of these components, as remnants, are nearly crystalline compounds.

● Sedimentary rocks are comparatively formed of uniform constitution though with streaked colouration due to seepage of dissolved substances and stratification.

● Extracted rocks, require dressing, and often downsizing. The cleavage or fracturing during dressing and fracturing depends not only on the basic classification of the stone and also on constituent minerals such as silica, quartz, feldspar, mica, etc. These aspects also define the types of tools used for working and the nature of surface finish possible.

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Igneous rocks, such as Granite and Trap are formed with the solidification of molten materials. Mineral gases and liquids penetrated into the stone and created new crystalline formations with various colours. Sedimentary rocks such as Lime stone, Sand stone, Soap stone Travertine, are formed from the bonding of deposition under pressure and heat over a very long period. Metamorphic rocks are formed by the transformation of igneous or sedimentary rocks, due to influence of heat or chemical action. Metamorphosed form of stones: Marble (of lime stone), Schist (of sand stone) and Slate (of mud-stone). Amorphous Solid is any material which does not have its molecules arranged in a lattice, or crystalline structure. Amorphous solids make up only 10 % of solids in the world. A well-known example of amorphous solid is glass, and that is why these solids are often termed glass. Amorphous solids’ structures have similarity to liquids, and so are also called supercooled liquids. Plastic is made from polymers, long strings of molecules purposefully chained together and is technically an amorphous solid. Crystalline Solids constitute nearly 90 % of all solids in the world. Crystalline solids have a lattice of molecules. The ordered pattern repeats substantially through the mass. Stones are classified as Siliceous when silica is the principal earthy constituent, Calcareous have carbonate of lime as the predominant material, and Argillaceous have alumina is the main component.

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WASTES AND RECYCLED STONES

Stone extraction or collection creates large quantity of rejected and broken mass. Site based dressing and downsizing, are mainly done to reduce the mass for transportation, These generates large quantity of wastes. As stone sites are very remote from the point of use or application, it is uneconomic to transport and use such waste materials. Downsizing and cutting workshops located near urban localities, have an advantage that the wastes originating here have consistent one face or dimension. Machines that dress a block with rotary or stripe saws create wastes with smooth finish on one or more faces. Similarly slabs’ end or edge cuts have a uniform thickness profile. Stone polishing machines provide ground particles which are used as filler media.

Angular cut wastes can be tumbled with iron bits in a rotary drum to achieve rounded edged pebbles. Stone wastes can be used to create cement and resin-based composites, and for ‘synthesizing’.

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Stone buildings that are demolished in urban areas end up as debris for land fill for lack of man power required for separation and re-use. However, in rural area, it is possible to separate and reuse the material. Older stone flooring units are thicker in comparison to modern supplies. This can be split into two or more units and use the cut-face as the new face. Similarly masonry or building blocks can be cut to thinner blocks for use in cladding or surfacing. The advantage in reuse is free supply of mature (weathered-seasoned) stones.

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Spolia (Latin, ‘spoils‘), repurposed building stone for new construction, or decorative sculpture reused in new monuments, is the result of an ancient and widespread practice whereby stone that has been quarried, cut, and used in a built structure is carried away to be used elsewhere. Entire obsolete structures, including underground foundations, are known to have been demolished to enable the construction of new structures. –Wikipedia

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Interpretations of spolia generally alternate between the “ideological” and the “pragmatic.”

Ideological readings might describe the re-use of art and architectural elements from former empires or dynasties as triumphant (that is, literally as the display of “spoils” or “booty” of the conquered) or as revivalist (proclaiming the renovation of past imperial glories). Pragmatic readings emphasize the utility of re-used materials: if there is a good supply of old marble columns available, for example, there is no need to produce new ones. The two approaches are not mutually exclusive, and there is certainly no one approach that can account for all instances of spoliation, as each instance must be evaluated within its particular historical context. –Wikipedia

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SHEER FABRICS and CURTAINS

Post -by Gautam Shah

A sheer fabric is very thin material which make it very translucent. Sheer curtains are also known as privacy curtains. Sheer curtains have ‘good fall’ or very soft bearing.

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Some of the best sheer fabrics are of pure silk, but most of the commercial curtain materials are made of synthetic filament yarn (long length fibres) like organza, polyester, nylon, etc. Many of the lattices like airy or net-woven fabrics are so pliable, flimsy and semi-transparent that they behave like a sheer fabric curtain.

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A sheer fabric has a natural graceful fall and allows light to filter through. Sheer fabric curtains nominally form the first layer in multiple curtains system. Such curtains allow a fuzzy view during day-time, but at night may require an opaque topping of a curtain. Sheer fabric must not be used with a lining fabric to maintain its translucency.

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Sheer fabric comes in a wide variety of colours, but white and natural shades of whites such as off-whites, cream, and ivory are popular. Sheer fabrics are also embellished and embroidered for patterns.  Such extra work, however, increases the weight of the fabric at the cost of graceful fall. Sheer fabrics are commonly heavily pleated and so the total quantity of cloth required for a sheer curtain is little more then a curtain of regular fabric. Sheer fabrics, due to their thin body and the lattice like weaves, offer very little insulation.

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Sheer effect is due to Diffraction of Light spreading out as a result of passing through a narrow aperture or across an edge. In case of curtain fabrics sheer effects are formed by latticed or net weaving. Similar effects occur due to the fuzzy transparency of materials like glass, acrylics, etc., and also due to the environmental conditions like rains, fog, sand storms, etc. Another remarkable sheer property for curtains occurs due to the pliable nature of fabric that adds to suppleness or fall.

Sudare screens

Sudare (簾 or すだれ) are privacy and illumination filtering screens. These are sometimes called Misu (御簾 or みす). The screen are featured in The Tale of Genji. Sudare have green fabric for hem. Sudare are made of slats of wood, bamboo, and other natural materials woven with threads. These are stiff but movable panels, or rolling-folding up screens of horizontal or vertical slats.

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