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

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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.

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

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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.

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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.

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STONES -viability now -1

Post 687by Gautam Shah

. Part 1 of Two articles

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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. There are other issues that are forcing reappraisal of Stone as the viable material of construction. The issues are > economics of transportation, wastage in production, and reuse of the material as debris and production residues.

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Stones, like the clays-soils are universal materials of construction and require very simple technology. There are Three essential sources of stone: 1 Surface collected stones, 2 Extracted stones, 3 Wastes and debris stones. Use of the surface collected stones in original size-form is easiest. Such stones, however, require down sizing and form dressing, before carriage to a place of use. Extracted stones are surface protruding and subterranean mass. These are often stratified or layered. Stone extraction causes ecological devastation due to removal of the top burden, large volume of reject-mass, and wastage of local cleaning, cutting and size dressing. Wastes and debris stones are man-made endeavours. Wastes occur at points of extraction and location of constructions, whereas debris occurs due to the demolition of structures. These need sorting, cleaning and transportation.

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To make Stones viable now, Technological Developments and Materials Management are required. Stones are used for their mass, surface and structural strength. These can be exploited further by new design, joint technology, assembly methods, formation of composites, improved structural geometry and conversion to different materials (chemicals).

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1 Extend the Surface Area: Stones are valued for their surface qualities and the prime need is to increase the surface area. The extended surface reduces the mass / weight of the stones. The surface area of the stones can be enlarged by two basic methods: by Thin Sectioning and by Amalgamation of bits and pieces, which otherwise end up as a collection and production wastes. Other methods of optimizing the surfaces are to endow new sensory qualities and surface properties. Many exciting technologies are now available.

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2 Exploring structural properties: Stones have certain directional structural properties which can be exploited and reinforced. The efforts start with new ways of excavation, extraction and conversion of the material. Other common processes are selection, orientation, rational sectioning and controlled aeration-seasoning. Structural potential of stones can also be exploited by developing new areas of usage and new techniques of construction.

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3 Stone’s Combinative formations: Traditionally stone composites have had lime and cement as the matrix component. The explorations now relate to composites with new forms of filler arrangements and new types of a matrix.

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4 Designing geometrical or spatial compositions: Stones shows great promise in offering radically different materials’ combinative formations. The formations include various ways of combining or ‘synthesizing’ materials of diverse nature, such as, with metals, polymers, ceramics etc.

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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. Though, qualitative consistency of man-made materials poses a great challenge to multifarious nature of stone materials. Stones have structural attributes, often called Engineering characteristics, which regulate their usefulness for conversion to: Building or Dimension stones, Veneered or thin slabs and for crushing. Similarly stones also exhibit very distinctive sensory properties that govern their use as a facing material in the form of building blocks, cladding and flooring slabs.

The opportunities of intervention operate on two fronts: Improvisations over existing methods and Adoption of radically different technologies.

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Part 1 of 2 articles

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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.

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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

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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.

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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.

surface-experience

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

 

BAKELITE PLASTICS -the beginnings

Post 583 by Gautam Shah

Clay was the first plastic material that could be formed to desired shape. Clay gains ‘plasticity-a moulding or shaping capacity, due to its grain shape, size and distribution and addition of water. A natural metal nodule or a purified one from the ore, on heating becomes, ‘plastic’. This property was not available with materials like wood and stone. Materials like Bamboo or Cain, have the capacity to bend, but cannot be reshaped or moulded. Plasticity is the property of material to be deformed repeatedly without rupture by the action of a force, and remain deformed after the force is removed.

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Potters clay > Wikipedia image by Yann

Historically few natural materials that exhibited the plastic behaviour were known, but without clear perception of the categorical behaviour. These natural materials were organic polymers or bio-derived materials such as egg and blood proteins. In 1600BC. Mesoamericans used natural rubber for balls, bands, and figurines. Treated Cattle’s horns were used for their translucency in lanterns and windows. Materials with similar properties were developed by treating casein -a milk-protein with lye. Casein was also used as gum material. Bitumen was used as a water proofing material for boats and also as a joint material for masonry. Plant-based starch materials on being cooked showed flow-behaviour. Lac, an insect exudate was used as gum or joining material in India. The lac was used for cast mouldings since 1868. Rubber, a plant exudate was used since 1535, as water proofing material and for shoe making.

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Cattle horn spectacles > Wikipedia image by Daderot

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Bakelite body Radio at Bakelite Museum > Wikipedia image by Robneild at en,wikipedia

Polymers were not distinctly identified till around 1900s, however during 1860s Thomas Graham noted that some dissolved organic compounds -typically cellulose, cannot be purified into a crystalline form. This was different organization of matter. Graham called them ‘colloids’, after the Greek word for glue =kolla. This was the beginning of the Age of Plastics or Polymer Age. (Plastic =plastikos Gk = mouldable) (Poly+mer=many molecules).

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Parkesine (London) developed the first plastic from plant origin cellulose by reacting it with nitric acid, to form a cellulose nitrate. Celluloid was plasticized with camphor, dissolved in alcohol and hardened into a transparent elastic material. On heating it could be moulded and coloured with pigments. It was a substitute material, for than (1860) widely used ivory balls for billiards. The product was patented under the trademark Celluloid. It was also used later in the manufacture of objects ranging from dental plates to men’s collars. Celluloid, despite its flameability and capacity deteriorate when exposed to light, was commercially successful.

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Ericsson Bakelite phone > wikipedia image by Holger.Ellgaard + sjalv laddat upp

The first totally synthetic plastic was the phenol-formaldehyde resin, Bakelite. In the early 1900s, Bakelite, the first fully synthetic thermoset, was reported by Baekeland. Baekeland’s was looking for a replacement for shellac that had difficult supply. And that is the reason, their first product a soluble phenol-formaldehyde like shellac was called ‘Novolak. Baekeland also worked on a process to strengthen wood by saturating it with a synthetic resin of phenol and formaldehyde.

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Bakelite chips colour chart 1924 > Wikipedia image

Baekeland reacted Phenol with Formaldehyde (an exothermic reaction) but stop the reaction midway, while the product was in liquid state (called A stage). ‘ The A resin (Resol) could be made directly into a usable plastic, or it could be brought to a solid B stage (Resitol) in which, though almost infusible and insoluble, it could still be ground into powder and then softened by heat to a final shape in a mould. Both stages A and B could be brought to a completely cured thermoset C stage, by heating under pressure. This last stage was Bakelite C, or true Bakelite.’
In 1927 the Bakelite patent expired and the market were flooded with competitive thermo setting resin products of Urea and Melamine formaldehyde, and other new thermoplastic resins such as cellulose acetate, polyvinyl chloride, poly-methyl methacrylate, and polystyrene.

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Bakelite, was recognized as the ‘National Historic Chemical Landmark’. Bakelite was mouldable material with electrical non-conductivity and heat-resistance properties. He saw a wide variety of uses of the resin with many different filling materials such as cotton, powdered bronze, slate dust, wood and asbestos fibres. It was used widely in electrical appliances replacing bulky ceramic components. It was used for kitchen handles, radio and telephone casings, kitchenware, jewellery, pipe stems, toys etc. His one of the first patents describes ‘Method of making insoluble products of phenol and formaldehyde’. Bakelite Company began to produce many material forms, but laminating varnish, was most successful products. Laminating varnishes are used for coating copper circuits, paper, fabrics and for manufacturing laminate sheets. Blocks or rods of transparent cast resins, known as artificial amber, that could be machined or carved to shapes were used for pipe stems, cigarette holders and jewellery.

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Old style vacuum cleaners with Bakelite body > Wikipedia image by Rosebud23

Baekeland’s heat and pressure patents expired in 1927 soon placing the company under severe pressure from competitors like Catalin. Catalin is also a phenol formaldehyde resin, but produced by a different, two-stage process. It was produced without any fillers like sawdust or carbon black. It can be worked with nominal carpentry tools like files, grinders and cutters, and polished to dull gloss. Another advantage of it was its transparency and capacity to take bright colours.

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Colourful buttons made of Catalin of 1930s > Wikipedia image attribution: Chemical Heritage Foundation

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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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HOW DO MATERIALS RESPOND ?

Post 453 -by Gautam Shah

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Stone Old Church Architecture Ancient Wall Gate

Materials respond to

Other Materials,

Environment,

User.

Old Wood Windows Shutters Architecture Broken

OTHER MATERIALS:

Materials respond to other materials within their realm. The reactions occur 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.

Federation Square Melbourne -tessellated grid Wikipedia Image by Cookaa

The response of a material, occurs through the surface, more emphatically, than anywhere else. Materials with their own surface systems (inherent finish) respond in the same manner as their body would. However, applied surface systems of the same or of foreign materials show different behaviour. In such reactions, the important factors are, surface preparation, application method, and bonding techniques.

Ecran_oled_flexible

ENVIRONMENT:

Materials are affected by many aspects of the environment. The effects are local, if environment effects are directional (through specific orientation), or occur comprehensively. The various constituents of the object also respond differently. Single, or mono material systems are often inadequate for such multilateral environmental demands. Multi-material objects or composites are conceived to serve such demands, separately as well as unitedly.

Farshid Moussavi, Detail, façade of Edificio Bambú =Bamboo Building Madrid Wikipedia Image from Francisco Andeyro (Alejandro García González & Francisco Andeyro)(www.arquima.es)

An applied surface material system, covering an entity, forms its own environment. Here the situation can also be equated to material to environment response.

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. 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.

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).

Material Response

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. A user perceives the surface of a material-object through factors such as:

EMP Museum founded by Microsoft co-founder Paul Allen in 2000, located at Seattle, designed by Frank Gehry

  • proximity (closeness, intimacy, distance)
  • duration (of encounter)
  • frequency and extent (area) of contact
  • mode of handling
  • our past experiences
  • our sensory capabilities
  • our physiological state
  • atmospheric conditions (temperature, humidity)
  • light (direction and level of illumination)
  • orientation, or point of observation.

Close up of a peyote cactus growing in the wild as mentioned in The Doors of Perception, by Aldus Huxley

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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NATURAL IRON OXIDE PIGMENTS -3 # Ochres

Post 408 –  by Gautam Shah 

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Ochres in Towns

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Ochre is an iron oxide pigment of natural and synthetic sources. Ochre are coloured soft deposit of clays often with mixed layers or pockets harder crystalline iron ore. Some of the best yellow ochre ’s are mined at Roussillon, Southern France. Here the mineral formations are naturally stained with colours to provide a wide variety of earth or natural iron oxide colours.

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The Greek word ochros, for Ochres describes it to a pallid or pale yellow, but natural ochers are brilliant colours. Ochres have a colour range that varies from yellow to deep orange or brown, due to the hydrated iron oxide. This is unlike the Red oxide which is from hematite powder, a form of iron oxide (Fe2O3). An ochre containing a large amount of hematite has a reddish tint, and is known as ‘red ochre’. The dominant yellow colour of ochre is due to the mineral limonite. Ochres are of two kinds, one with an argillaceous or clayey basis has richer colours, whereas the other with a calcareous base is slightly of ‘flatter’ colours. The nature of the associated minerals affects the colour, such as calcareous varieties have brownish-red and dark-brown shades, and aluminous types offer red and violet tints.

 

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Different colours of Ochre pigments are extracted from different veins, and then mixed to obtain specific shades. Other shades are created by roasting (‘burnt’ or calcination), and dehydrating the mineral clays.

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Yellow Ochre is a very ancient pigment. It is without any trace of green. The oxide colours are called Earth colours, due to their richness, brightness and warmth. Ochres are mixed with high refractive whites like Lime (or zinc, titanium dioxide), or low refractive ‘extenders’ such as the barytes to achieve, respectively, high opacity or translucency.

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Manuscript Cover India in Ochre colours

In Ancient Greece, red-ocher was called miltos, (hence Miltiades red-haired or ruddy). In Athens when assembly was called, everyone was supposed to attend it, and failure to attend it incurred a fine. To prevent people loitering around slaves swept the open space of the Agora with ropes dipped in miltos . It was also known as raddle, reddle or ruddle. In Ancient Egypt, the ochre was often used in place of gold, which was considered to be eternal and indestructible. It was used for painting tomb interiors in place of toxic orpiment (an orange-yellow coloured arsenic sulphide mineral). Ochre was used for painting women’s faces. Romans used the yellow ochre to to represent gold, skin tones, and as a background colour in their paintings such as the murals of Pompeii.

Egyptian Ochre colours

A rational process for refining ochre pigment was developed by the French scientist from Roussillon province of France, Jean-Étienne Astier (1780s). He washed the clay to separate the grains of sand from the particles of ochre. The decanted and dried ochre was crushed, sifted, and ground as the pigment. Best of the qualities were used for artists’ colours.

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Ochre robed Sadhus sitting on the Vishnu Temple of Kathmandu’s Durbar Square, Nepal Wikipedia Image by us Koljonen (Dilaudid)