DAYTIME INTERIOR ILLUMINATION -REALITY and PERCEPTION

Post 486  by Gautam Shah

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Landscape Lattice Ceiling

 

Illumination is required in interior spaces in several contexts. At realistic level, task illumination is the most obvious requirement, but one needs sufficient illumination to move around known as well as unknown interior spaces. At perceptual level an illuminated space is associated with cleaner and healthier space. The perception has been so ingrained into our psyche that interior brightness and well-being of the space as one concept. For ages, in absence of glass, openings were ‘open’, allowing sufficient ventilation through the cracks and gaps in the door or windows. And even when openings began to be glazed, the sunlight seeping through it warmed up the interior space to cause air movements, and act as bactericide.

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USCapitol_-_Capitol_Visitor_Center_Skylight_-_U.S._Capitol

In Northern hemisphere, the North, and in Southern hemisphere the South, gets solar exposure throughout the day. And so, at realistic level, the North and South facing openings are chosen for illumination in factories, schools and homes. But perceptively, it is the East, than west, or combination of both, have found favour, for religious buildings. East-west light is nearly horizontal in the morning-evening and penetrates deepest section of a building. It is varying hour by hour, unlike the consistent North-South light. East-West light is dynamic and awe inspiring. In early Egypt the Sun god was revered and the main doors of temples were East facing. North and South doors have high inclination of the sun, so horizontal penetration of illumination is not very deep.

West front of Wells Cathedral UK

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Door orientation has a direct bearing on the level of illumination. Early Church buildings had Eastern entrances to illuminate the altar from front, but an altar with an Eastern back-lit glass windows proved to be a better alternative. Gradually churches began to have Western entrance doors. The East-West have been prime directions for illumination in many historical buildings, however, with the ascent of the clear storey openings the importance of a door as the chief illumination provider has decreased.

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The size and Width-Height proportions of a door have a direct relationship with the depth of illumination. A taller door is more effective then a wider door in illuminating deep interiors. Monumental buildings have tall doors not just for architectural grandeur, but the upper section of a tall door provided the deep illumination during a crowded ceremonial function. In Egyptian temples the upper section of the door was supposed to bring in the Sun god with the first rays of rising sun. The tall doors were unmanageable for shutter mechanisms and also too narrow for ceremonial passage. The upper section was either left without a shutter, or latticed to form a ‘transom’. It was more practicable to leave a transom or a rose window than load a wall over the door lintel.

Inside_one_of_the_rooms_of_the_Rang_Mahal

The illumination through a door has also been enhanced by providing side lites or sidelight and also ‘within the door’ with lattices. Greek buildings had panelled doors that were partly latticed in the upper sections, or had additional latticed shutters. Side lights or side windows decrease the size of the shutter and reduce the structural span of the lintel, but increase the perceptive width of the opening.

Shipping Warehouse Bay Industry Storehouse

Illumination through a door invariably accompanies the radiation. The solar radiation through a door varies depending on the geographical location, orientation, time of the day, shading devices, nature of the foreground and surroundings, etc.

Puerta del Perdón, Catedral de Toledo, España Pic by Sevillista on Flickr

The depth of the door (depth of the wall) defines the quality of illumination. A door in a very thin wall (Gothic architecture) -the flush set door, allows fuller distribution of light, (a larger segment of brightness on the inside), but a deep-set door curtails the brightness due to the sides of the wall. In Gothic cathedrals due to side buttressing the side walls were thin and allowed flush set openings (with stained glass), but the same structural advantage was not available in case of un-buttressed front walls. The entrance doors of Gothic churches were deep set in thick walls but with serrated edges. Door sides (i.e. wall sides) and heads have been chamfers cut, on inside or outside faces, to enhance width and height. Chamfered edges on outside make the opening flush on the inside wall, and allow wider perception of the outdoors. A bevelled edge on the inside, make the opening flush on the outer edge of the wall. It allows visually more perceptible brightness on an interior surface due to the additional lit surface of the bevelled faces.

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PAINTING WHITE – 2

Post 485  by Gautam Shah

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During 1930-50s Paint shops used to offer Oil-bound Distempers (OBD) and combination of Zinc pastes and double-boiled Linseed oil, for household painting. These were mixed with pigment pastes for shade creation. Post 1950s ready mixed oil paints or General purpose enamels (GP) became popular. But than paints’ shops had to stock several tins of different measures, for each of the shades and varieties (oil paints, distemper paints, flat and egg-shell plastic paints). And to match a desired shade, it was necessary to buy small bottles or vials of concentrated pigment pastes called tinters and top up an available shade or create one from a white.

Paint Shop of earlier era

There were two whites available, a ‘super-whitewith some form of ‘optical whitener or brightener, an ‘opacifier’ or colourants like blue or violet, and pure stuff called base-white, without any additives. Few lay people were aware of the later variety, or considered it to be some inferior stuff due to its less romantic name (super white versus base-white), and discounted price.

Zinc paste-based paints and General purpose enamels had linseed oil or its alkyd resins as the chief film forming material. The linseed has a tendency to oxidize and turn yellow over the age. This began to change due to strong demand from manufacturers of white-goods (consumer goods painted white such as ovens, fans, washing machines, refrigerators, etc.) for long-term non yellowing finishes. This led to use of non yellowing oils for resins, and new generation formulations of Urethane, Amino resins and epoxies. The same innovations began to percolate to home-paint markets. From 1960s Plastic polymer-based emulsion paints (called Latex paints in USA) began to be available. This offered non-yellowing white paints.

Shade Card

Titanium Dioxide as a whitest pigment had few technical problems of paint formulations, but these were initially solved with use of Zinc and Lithopone as additives. Oil paints in glossy and flat varieties, and Plastic Paint with, sheen, egg-shell-matt and flat varieties now were offered as one or two coat systems. This high hiding-covering was due to excellent pigment grinding-dispersion in machines like attritors that replaced ball and roller mills.

United States Capitol west front

Paint markets are now radically changed. Paints manufacturing companies depend on shops to match the colour shades. The shades are created from basic, and few vials of ground pigments, which inject exact-micro quantity of colours into range of base formulations. The base formulations, include nearly clear to several types of white paints. White bases have natural shades of white pigments, and some have whitening-opacifiers. A white base is used for light tints, but not more than 100 ml paste can be added for darker shades to avoid loss of gloss or the effect on drying time. A neutral, pastel or mid-base contains lesser quantity of white pigment and is used for creating darker colours. And a clear base is used (it may contain white powders of low refractivity or extenders, but is free of high refractivity white pigments), for very deep colours. Some manufacturers use this base to add little sheen to matt paint.

Whites are affected by surroundings and show many variations

Whites are affected by smallest amount of additive colourants. These colourants may come from residues of earlier colour in brushes or rollers, any loose particles on the surface to be painted and thinners (solvents and water). Some additive colourants, if not thoroughly mixed, begin to darken the colour shade over brushing or rolling. Extra ordinary care is required in selecting, buying, mixing and using, white and ‘off-white’ shades. Shops have a file of colour shade cards, which are rarely fresh. The shade card viewing must be done in natural light, as it is affected by the surroundings and type of illumination. Shop computer calibrated and mixed shades, are not necessarily exactly right as per the shade card or as per your need.

A colour shows many variations at different angles of viewing and so colour matching must be done perceiving it from as many positions > Pic by https://www.flickr.com/photos/horiavarlan/4271993197

One of the best ways is to buy a small trial pack, and apply it on two different walls (preferably at right angles), at the site location. Once a right shade is achieved, leave some quantity (see the next paragraph) in the trial pack for master batching and matching.

HOW to mix a white shade with very light tinge of other colours at home? Buy the most appropriate white-base out of several ones available at a paint shop (usually 2-6 varieties). Now separately mix the concentrated tint to small quantity of white-base, with shade as close matching to your desire. Such faint tinges of colours are very difficult to visually perceive. So place a drop of experimental mix over the quantity left in trial pack. Your shade will be either darker or lighter, but easily perceptible.

White shades1

Most plastic emulsion paints now have a ‘Thixotropic’ compound, which gives a heavy, butter like false viscosity to the paint, to prevent separation or settlement of heavier phases or solids. Stirring is required to reconvert the stuff to a temporary liquid phase. Plastic paints come with good odours, to suppress the unpleasantness of paints, but one need not judge a paint on that count.

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HOW DO PROFESSIONALS and CLIENTS SEEK EACH OTHER ?

Post 484  by Gautam Shah

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Professionals and clients seek each other in a variety of ways. A client can go about it without any inhibitions, whereas a professional can go about it with certain restrictions, depending on the type ethics followed by the profession. Client and professional come to know about each other primarily through intermediaries like friends, relatives and so on. However, in a rare case, the client may contact a professional directly after seeing or experiencing the work as a real entity, sketch or a publication about it.

CLIENTS’ approach

A lay-person as an Individual is always free to appoint any person as an adviser or helper for the professional services. Here no Government regulations or rules of the professional bodies like council or guild can be operative. Perhaps by dealing with ‘unrecognized professional’ one may not get legal protection or redressal.

When an organization, as a client is not allowed, or authorized to deal with any professional, on a person to person basis; a process for an appropriate selection of a professional is required. The process of selection begins with invitations offered to:

  • any competent member of society,
  • member of bodies with a certain level of competence
  • members of a body who necessarily have certain level of competence.
  • persons belonging to a certain geographical region, experience, age, sex, nationality, religion.

For complex jobs, selection of a professional is done through a competition, wherein professionals are required to tackle certain essential components of the job, or offer a holistic concept towards the issue.

Intermediary

A client may not contact a professional, unless there is some foreknowledge, reference or suggestion by someone. This usually comes through another professional, like a financial adviser. Members of the society usually know where and how to locate professionals of well established or traditional fields. However, in newer branches of human skills, the professional and the client do not have an appropriate forum to interact. In such situations, the intermediary professionals help to bring together the potential clients and professional.

PROFESSIONALS’ approach

A professional on realizing a person’s potential as a client, may seek the person directly or through a mutual acquaintance or a friend. However, if the person concerned is a potential client in the official capacity (employed official of Government or private organization), than an official appointment with the clear declaration of intent is necessary.

A professional can seek a client in a variety of ways. Most of the professional bodies regulate a professional’s exposure and consequently the behaviour with the society in general and with potential clients in particular. Many professional bodies discourage direct advertisements by professionals to seek clients and assignments. “An advertisement however effective cannot project the professionalism or the competence of a professional”. It provides an undue advantage to the user.

Lawyer of the years

Most professional organizations believe that professionals should receive jobs in proportion to their professionalism and not their capacity to project through media. Paying out any consideration or any promise to that effect, to procure a job is also considered unethical. Problems of this ground arise; when a person is a client on the basis of the official position (so is capable of selecting / appointing and compensating a professional).

1024px-Consultation_-_Health_Check-up_Camp_-_Howrah_Swamiji_Sangha_-_Dumurjala_-_Howrah_2015-04-12_7598Cultivation of social contact is the most common method for a professional to come into contact with a potential client. Other Personal approaches include, specific letters, generalized bulletins, telephonic calls and face to face meetings. The impression created through a meeting or telephonic call may not be of desired type and intensity. Letters are very objective, last longer but have to be brief to be effective. Professionals get clients from other professionals. Here their competence is assured by the referring person.

Bio-data or resume is ever lasting, and very effective medium of exposure. Bio-data may contain basic information about the person, professional achievements and competence. Bio-data could be a very specific document, prepared (tailor made) for a potential client or could also be a generalized document that may serve to a set of potential clients with similar needs. Bio-data could be a very general introduction, good for any person whether potential client or a lay person.

A bio-data that is tailor made, may reveal or emphasize data that is relevant to that particular exposure. Concealment or non emphasis of data in such a bio-data is intentional and is generally not unethical though could be malafide. General bio-data tends to create impression of a commodity pamphlet. Creative professionals generally do not favour this type of medium. Internet has become an ideal medium for placing a Bio-data. A digital document is very flexible and accessible worldwide.

In dealings with clients, what kinds of behaviour, actions or attitude are considered as unethical, malafide or bad, varies from country to country, region to region, profession to profession, and time to time. In professions where rules regarding behaviour have not been formalized, it may vary even from a professional to professional.

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PAINTING WHITE – 1

PAINTING WHITE – 1

Post 483  by Gautam Shah

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Painting anything white is easier said than actually achieved. Lovers of white are like ‘platonic lovers’ and so are confused as to what colour needs be used. The sensual lethargy arises because there are too many tinges, chroma, hues and tones of colours in the market to select from, and earlier affairs have been disappointing. Some lack the daring to experiment, or incapable of orchestrating coordinated response with the variety. And to this, the response is extremist, not only white is sought, but want whitest white and everywhere. The maddening craze cannot be achieved on own, through a painter, or a novice designer. It needs help of a person of experience with technical know-how.

White Sands Pensacola Beach, Florida USA

A white colour seems different to different people, in specific environmental conditions, spatial settings, and most importantly in presence of other colours, in proximity or even memory. There are many examples of whites around us, Clouds, vapour, milk, flowers, teeth, bones, cotton, snow, swans, ducks, rabbits, and skies. Then why is it so difficult to colour anything white? Nature has provided one of the most abundant materials to create the white, Lime or Calcium Carbonate. There were several other minerals like China clay or Kaolin (so-called after the towns of Gaoling or Kao-Ling in Jiangxi province, China), Magnesium carbonate (Magnesium was first discovered outside of the Greek city of Magnesia), Talc, Diatomaceous earth, Marble dust, etc.

White Cliffs of Dover

 A white is effective due to the high refractive index. Lime powder and gesso (China clay, gypsum), were the first whites available in prehistoric times. These were used for levelling the surface and for creating a white ground. As per the modern day terminology both the materials are not white pigments, but extenders. A white pigment has refractive index, above 2.0 (Titanium Dioxide Rutile grade -2.73, Titanium Dioxide Anatase grade -2.55, Antimony Oxide 2.09-2.29, Zinc Oxide -2.02, White Lead basic Carbonate 1.94-2.09), where as most extenders have refractive index range of 1.65. This in very simple terms means that a white colour will have low covering-hiding capacity and so seem ‘dull’ or transparent white, if entirely or partly made of extenders. A white colour of Titanium Dioxide will seem ‘full’ or opaque white.

by JJ Harrison (jjharrison89@facebook.com) Wat Rong Khun, Chiang Rai, Chiang Rai Province, Thailand

Pigment Volume Concentration -PVC is relative proportion by volume of pigment to a resin (binder). Glossy paints have lesser volume of (17%) pigments compared to semigloss 25 % and flat paints can have 38-40 %. It is preferable to use a flat paint over fresh plaster, as it levels the surface better, but a flat paint on a virgin surface may look extra flat, due to greater absorbency.

Pic by Luc Legay on Flickr > Fascination of all White party

Lead white was used by artists and decorators for several centuries in spite of its known toxicity. Greeks called it Psimithium and Romans Cerusa. Most of the older classical oil paintings were created over a lead white canvas primer coat. White Lead or Basic Carbonates pigment in linseed oil paints offered good adhesion and brush-ability and so was used for creating highlights in canvas painting. Zinc oxide, was known as a medical material for open wounds as mentioned in the Indian medical text ‘Charaka Samhita’, from 500 BC or before. Zinc white was accepted as a pigment for linseed oil-based paints for paintings by 1834. Lithopone is a white pigment, a mixture of barium sulfate and zinc sulfide. It was used as a substitute or supplement for toxic white lead.

National Library of India Calcutta

Titanium Dioxide as a white pigment was discovered in 1821, but its commercial use as pigment began in 1921. It has a tinting strength far superior to any other white. In artistic oil pastes, it dries to a spongy film, so needs to be mixed with Zinc or Lithopone. Cheaper brands of paints or Oil bound distempers (OBD) often use titanium dioxide mixed with barytes or other pigments, but at the cost of brilliance and tinting strength. Titanium dioxide ranges of pigments are nontoxic.

Oia Santorini Greece

To be continued to Painting White -2

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COATINGS as thin Surfacing

COATINGS as thin Surfacing

Post 482  by Gautam Shah

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Coatings are thin surfacing with or without a colourant additive. The colourant if present, may be transparent, translucent or opaque. Coatings consist of many different components, such as a film forming substance, and additives like, colourant, reactive agents, solvents etc. In a very complex coating composition such clear-cut distinctions are not apparent, because film forming substances and additives serve purposes beyond their nominal roles. Historically coatings were created as art medium for illustrative and decorative effects. These then began to be used to alter the appearance, improve the tangibility and to provide a protective cover to objects and human body.

Toroid_electronic

Phenolic Varnish coated Copper coil

Coatings are used for 1 changing the quality of the existing surface, and 2 applied as a permanent cover over an object. In the first case the changes are just few molecules deep, like: removal of few molecules of the object or some products from the surface section, rearrangement of the molecules, varied chemical formulation. In second case a composition is applied as a permanent coating, through bonding processes like adhesion, cohesion, chain linking, and material-phase change, intermolecular interactions including van der Waals forces, hydrogen bonds and strong covalent bonds.

Internal coating

Surface Treatments form a very important section of coating technology. Some surface treatments are temporary and are removed once the required action is accomplished, others remain as full or partial deposition. Many surface treatments serve specific purposes such as cleaning, roughening, smoothening, etching, moisture proofing, rust inhibiting, air barriers, static arresters etc. Some others only facilitate the application, setting or drying of the coating.

Anti Glare / Anti reflection coating on Glass

Traditional Coatings are usually liquids of low solids content. These first ‘dried’ by evaporation of substantial content of organic solvents, and later ‘set or hardened through oxidation and long chain formation. This technology began to fad out with use of Plastic or latex paints. These are applied as aqueous dispersions or water-based emulsion of polymers. Now formulations are also solvent less or powder coatings.

Micro Surfacing Road Paver

At application-stage the film-forming mediums are in various phases such as liquid, solid or vapour, or a combination thereof like, suspensions, solutions, dispersions, emulsions, thermoplastic compounds, thixotropic compounds, etc., but coatings once applied ultimately settle to a heavier phase, usually (but not necessarily) a solid phase.

Roof underside fireproof coating

At an application stage a lower phase helps in many ways. Mainly due to liquid state there is uniform and thin level of application. Liquid state of the material permits better dispersion of costly or rare constituents. During application the integrity (thorough dispersion of constituents) can be maintained. Energy required for application of coating is very small. Liquid coatings can be formulated for varied but controlled deposition and rate of phase conversion, to match the substrate and environmental conditions.

Glazed Bakery products

Coatings form a continuous film and so do not have joints, except at junctions where coating application is delayed (a dried out portion and a fresh coat touch each other or overlap). Coatings are thin surfacing so the coated entity remains malleable, and allow the post-forming operations (e.g. coated metal sheets). A coating film has a thickness ranging from 0.0005 to 0.5 mm (0.00002 to 0.02 inch). Coatings are deposited on the entity by many different techniques such as daubing, brushing, spraying, screen printing, roller coating, and dipping.

Wood Deck staining – Coating

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LEGENDS of OPENINGS -3 Door and the Sun

Post 481  by Gautam Shah

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The Door and the Sun are omnipresent in this world. The Sun relates to the horizon, from where it appears. And the Door in spite of its portal of sides and threshold is held by the lintel head. The skyline is a reachable limit, but the lintel head makes a door godly or human. For Gods, the threshold is inessential but for mortals it is ubiquitous hurdle and challenge. The sun rises at the edge of the earth, at different points and time, but its reincarnation is inevitable, yet reassuring. Mystically the sun opens the door with a new day of changed fortunes.

Helios Greek God on Chariot (Greco-Roman mythology) NW pediment of temple of Athena in Ilion (Troy)

The sun takes many forms of travel across the sky, some realistic and other symbolic. Sun flies like an eagle, swims like a crocodile, drifts like a tortoise, ride a regal chariot with seven horses, floats with a boat or glides on the light rays. The sun’s passage has also been represented through flying, moving and rotating objects such as the wheel or dharma chakra, flag, toran, festoons, light mobile objects and shiny metal spirals. The sun’s rises in distant hills, ocean or landmarks but its arrival is celebrated as a passage through some built-forms such as an opening, gate, portal, arch, door, a colonnade of pillars or obelisks.

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Japanese Sun Goddess Amaterasu emerging from a cave or opening bringing out sunlight back to Universe

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Pharaoh Akhenaten and family worshiping the opening, the Aten with rays emanating from the solar disk

The Chariot of Greek solar deity Helios

Helios, a Greek solar deity drove a fiery chariot through the heaven by day, but at night floated back across the ocean in a golden bowl. The Egyptian Ra. swept across the sky in the sun-boat. The Japanese Sun, the king of nature comes like a bird, and roots over the bent beams of the Tori gate.

Shimogamo Jinja no Tori

Early Egyptian places of worship were entered through a cleavage formed by parallel pylons. It had set of shuttered doors at the bottom, just of height to conceal the magical ceremony preparations. The lower shuttered portion was for the mortals, but upper section was left open for the Sun god to enter. Ordinary mortals need a threshold, a mark of opening, but an ethereal god like Sun or Ra. needs no threshold. The god Ra. enters from high up so required no lintel or door head.

Ra in his solar boat

Egyptian’s temples and tombs had two openings: the East and the West one. The East door was real, for the dead body and soul to arrive. But the West door was a false or make-believe entity, known as ‘Ka door’. It allowed the Ka (the soul) to pass through onto an eternal journey. The False door was not a replica of the real door, but a metaphoric presentation of exit or departure. It had an offering niche, for real and imitative offerings, a stela with hieroglyphic inscriptions that contained the wishes for the afterlife and prayers or entreaty. It was a threshold between the world of the living and the dead.

Stele_or_False_Door_to_a_Tomb_by_Boston_Public_Library

False Door

Peruvian people, believe in a prophesy that God will appear in the light ship through the portal called ‘Gate of the God. It is a gateway to the lands of the Gods. The legend tells about heroes who had gone through it for a new life of immortality, and occasionally return to check the affairs of the kingdom.

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Peru Door of the God

The idea of return fills the mortals with hopes. A door is duality of two heads of Janus (the God of doors), as that of Sun and Moon. A door is as much for departure, as for return, or as in Sanskrit for Aagaman and Nirgaman. But life after death is uncertain, so complete your home duties before you step out and accomplish your tasks before you step in the door. Christ says ’small is the gate and narrow the road that leads to life, and only a few find it’ (Matthew 7:14).

Inspiration for Mid Lands

Author J.R.R. Tolkien (of Hobbit, 37, Lord of the Rings and Silmarillion) talks of Door of Night and Door of the Day.

The Sun was to pass through the Door of Night as it travelled above Arda. When the Sun passed through the Door, night would fall upon Middle-earth. The Moon would then rise from its resting place and continue on its path over the Earth. The Sun would traverse the border of the Wall of the World, re-entering the world in the East, at the Gates of Morning. At the same time the Moon would be sinking in the West and a new day would begin’.

Gateway of the Sun from the Tiwanku civilization in Bolivia (restored version)

Rear view 1903

Sun God Image over Door Head

Dharma Chakra Sanchi India

A high level object reveals the arrival of sun. It could be a dynamic object flying in the air and scintillating in the golden dawn, or static, gilded and decorated door head. The moving Dharma-Chakra of the Buddhist temples and stupas and over a Stambha -pillar had this purpose. Sun rays also shined the metal-clad tops of tall obelisks. It also lit up the moving flags, torans and festoons. The door heads had Sun, symbolically as eagles, rayed globe or heads. A Canton tomb door head is sculpted with the sun rising from the clouds. A falcon headed sun god Horus, after a battle with darkness took the shape of a human-headed lion, the sphinx or ‘sun on the horizon.’

Egypte_louvre_091_faucon

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POLYCARBONATE

POLYCARBONATE

Post 480  by Gautam Shah

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Polycarbonate is a tough plastic valued for its transparency. It has very high impact resistance combined with light weight. It is, 1/3 the weight of acrylic, and 1/6 of glass. Acrylic is 17% stronger than glass, where as polycarbonate is nearly unbreakable, being 400 times stronger than glass. It is very ductile, self extinguishing and flame retardant plastic. It remains dimensionally stable in prolonged sunlight exposure. Polycarbonate is more expensive than Glass or Acrylic. It is recyclable and environmentally preferable to PVC. Polycarbonate is attacked by many organic solvents. It is also fairly expensive compared to other plastics.

Ajinomoto Stadium

Polycarbonates were first discovered in 1898, but remained without commercial exploitation for 30 years. In the post war period research resumed in 1953, with Bayer patenting the first linear polycarbonate. One week after this GE USA independently synthesized a branched polycarbonate and filed a conflicting patent. After the patent priority resolution, Bayer began commercial production under the trade name Makrolon in 1958. and GE began production under the name Lexan in 1960. After 1970, the original brownish polycarbonate tint was improved to glass-clear.

Polycarbonate is a versatile plastic, which can be injection moulded, extruded, blow moulded and thermo formed. Unlike most thermoplastics, polycarbonate can undergo large plastic deformations without cracking or breaking. It can, as a result be reshaped at room temperature by using techniques for sheet metal working. This makes it valuable for model or prototype making applications. It can be joined mechanically, solvent bonded, and welded with skill. Virgin polycarbonate is the original polymer, whereas re-ground polycarbonate is waste that has been prilled or formed into pellets. The properties do not change much after such prilling.

Polycarbonate Police shields

Polycarbonate is an amorphous thermoplastic of long-chain linear polyesters of carbonic acid and dihydric phenols. They are called polycarbonate because functional groups of polymers are linked by carbonate groups. An amorphous (non crystalline) polymer has a glass like, transparent appearance due to the random orientation and intertwined nature of its molecules like spaghetti. Polycarbonate has a glass transition temperature of about 147 °C and so begins to soften gradually above this point. It begins to flow at about 155 °C. Working tools or forming nozzles are held at above 80 °C temperature to get a product with a clean surface. The toughest grades have the higher molecular mass, but are more difficult to process.

Twin wall Polycarbonate Sheet

Polycarbonate water bottle

The prime uses of Polycarbonate relate to its transparency, toughness, lightness of weight, and exterior durability. Some of the uses are unbreakable openings’ ‘glasses’, roof domes, greenhouse enclosures, police riot shields, vandal-proof light shields, partitions in taxis, non rattling ‘glass’ for bus and tram sliding windows, bullet and temper-proof covers for the valuables and exhibits. Its easy form-ability allows its use for transparent gift and jewellery boxes, utensil covers, bodies of gadgets like hair dryers, housing for electric meters, switch covers, funerary caskets, safety helmets, and computer parts.

Polycarbonate Greenhouse

Polycarbonate has excellent transparency, durability, and high a refractive index, and so is used to make eyeglasses. A thin polycarbonate formed to required curvature makes it very light in weight eyeglasses for spectacles. The clarity, scratch resistance and ability to take on transparent colours makes it suitable for inspection glasses in industries, air craft interior fittings, mines lights, high voltage switches, sockets, back-lit advertising display boards, see-through floors and bottom lit dance floors.

CDs and DVDs

During the last decade polycarbonate is being used for making CDs and DVDs. Polycarbonate like ABS plastic can receive sputter deposition or evaporation deposition of aluminium without the need for a base-coat. Polycarbonate composites are used for marine utilities like boats, frigates. The addition of glass fibres to polycarbonate increases the tensile strength, flexural strength, flexural modulus, and heat deflection temperature.

cockpit canopy of the Lockheed Martin F-22 Raptor jet fighter