SPACE PERCEPTION and ILLUMINATION

by Gautam Shah  ➔

The space and environment mould each other, and jointly define a process of perception. Perception of space and environment helps to know about position, context, constancy of things, and features, postures, and gestures of inhabitants’. Perception of space and environment helps in improvising our expression and communication, and thereby our behaviour. Here two processes are considered vital: How a person will perceive others, and How others will sense the person?

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A strong back illumination makes it difficult to perceive a Chair-person’s features and gestures

The position of a person, in terms of the body posture, visibility, stability or consistency and the background context, etc., are issues how others sense him or her. Similarly a person trying to project self must be aware of the perceiver’s distance, angles of connection, social dependency and postural condition. The process of perception is a two-way affair.

Position of a person relative source of illumination is a very important consideration for Space Planning.

In a dwelling, head of the family occupies the head position at the dining table. This position at the far end of the room, is often set against a window. The window from this perspective illuminates everything (people and objects) during daytime, such as breakfast and lunch periods. The head of the family gets a well-illuminated view and so feels commander of the situation. At the same time, however, other participants on the dining table see (in the reverse position) the head of the family against a brightly lit window. This occludes perception of details of the body posture and facial gestures. As a result of this family members derecognize and ignore the head of the family. Wife of the head of the family, if she occupies the opposite chair, or if the kitchen is in that direction, she too disregards the position and cold-shoulders the person.

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Strong back illumination makes it difficult for customer to see the bar tender’s face However, Bar attendant can clearly see customers.

This daytime happenings, change considerably at supper time, as the ‘backbite window’ illumination is replaced with artificial lighting. Nominally the situation should stand corrected (if not reversed), but attitudes formed during daytime persist at other times.

In a related space planning setting, the person in charge of cooking has to face the platform, and therefore show the backside to the dining table sitters. And this becomes cause of devaluation of the ‘person in charge of cooking’. This is now being corrected with island cooking facilities, or cooking and dining being placed at a right angle. Correct direction of lighting vastly improvises the situation.

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A strongly back lit room

Position of a person relative to the source of illumination also holds true in conference rooms, executive cabins, reception areas, lecture rooms, press conference rooms, etc. Natural or artificial illumination -as singular source and that too from the backside must be avoided, and if inevitable, reinforce it with lighting from other directions. One of the simplest ways is to envision how the situation manifests from every single position.

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Two persons getting side illumination recognise each others features, but third person at the end of table may not be able to read facial gestures

Side illumination eliminates many of the anomalies of perception and recognition but not all. To create good diffusion, the source for side illumination needs some depth from the seating -standing position. In small rooms this is not possible, so it requires reinforcement with lighting from other directions.

Exclusive illumination from top, through spot light or skylight creates under the chin shadows. This can be corrected by counter illumination from other directions. Light colour floors and table tops can counter the effects of top -down lighting. TV studios use light colour or reflective table tops, but avoid showing them in a visual frame by positioning the participants on a raised platform, and cameras at a slightly lower level then the table tops.

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PAPER -part 3

by Gautam Shah

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PAPER FORMING

Paper forming means forming or casting a sheet of paper from the pulp over a surface that will allow removal of water. The pulp nominally is 1 Lt of water and 1 to 10 grams of solid matter. For draining off the water a bed of wire mesh, deckle, fabric, etc. are used. The quality of pulp and the forming process determine the basic nature of paper. Later processes of conversion further modify the surface qualities.

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Hand-Paper making

The differences between various grades and types of paper are determined by:

1. Type of fibre or pulp

2. Degree of beating or refining of the pulp

3. Addition of various materials to the stock

4. Sheet formation method, basis weight or substance per unit area

5. Physical or chemical treatments after paper formation.

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Paper is produced by three basic processes:

a. Hand made or traditional way

b. Mould made or semi-industrial way

c. Machine made or fully industrialized way

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HAND MADE PAPERS

The basic process of making paper has not changed in more than 2,000 years. It involves two stages, the pulp forming and the formation of felted sheets. The pulp suspension is spread on a porous surface, to drain out the excess water. The pulp forming process may be partly mechanical or chemical but sheet formation is a hand operation.

In making paper pulp by hand, an appropriate mix of raw materials is placed in a vat or trough and is pounded with a heavy pestle or hammer to separate the fibres. During this phase the material is washed with running water to remove impurities. When the fibres are sufficiently broken up, they are kept in water suspension. At this stage the pulp, called half stuff, is ready for the actual process of paper making.

Paper is formed over a mould, a reinforced sheet of metal mesh having either a square mesh pattern, called a wove-pattern, or a pattern of more widely spaced longitudinal wires held together with smaller transverse wires, called a laid pattern. The mould pattern imprints itself on the finished sheet of paper. Handmade papers that are not given special finishes are identified as wove or laid papers, depending on the style of mould that is used in their making.

There are TWO processes for manufacturing hand made papers.

1. A framed wire mesh -mould, called a deckle is dipped into a steam heated pulp tub. When the frame is removed from the vat, the surface of the mould is coated with a thin film of fibre-water mixture. It is given a shake to orient the deposition of fibres in all directions. It also causes the individual fibres to interlock with those adjacent ones, giving strength to the sheet and allow drainage of much of the water from the mixture through the mould mesh. The frame along with the deposited mass is allowed to settle until the paper is sufficiently cohesive to permit its removal from the deckle. The paper is then transferred onto a felt blanket. Several layers of blankets are pressed together to remove the excess water. The sheets are then separated and allowed to dry in a natural or forced air ventilation system.

2. In the second process, the wire mesh frame is nearly similar. But instead of dipping the frame in the pulp tub, the pulp is allowed to float in horizontally, or is poured over a submerged mesh. The pulp is levelled with jerks. The entire frame is placed in a shaded area to drain and dry. Pressing if any occurs much later and often without interleaving of felt blankets.

A major structural feature of a paper web is the lack of uniformity in weight per unit area. Minimizing these variations involves skill. Dilute suspension of fibres (1 to 10 grams of dry solids per litre) in water is allowed to drain through a net (woven polyester fabric) to leave behind a coherent layer 6 to 18 mm deep and several metres wide are formed. A visible change occurs in the appearance of the stock, as it reaches a concentration of 20 g, dry solids per 1 litre, its surface ceases to be mobile, loses the liquid sheen and becomes matt. At this stage natural drainage stops, further forming is done by vacuum removal of water and pressing by a roller.

The sheets of paper are separated from the felts, stacked, and pressed. The process of pressing the stack of paper is repeated several times, and each time, and the stack is built up with the individual sheets in different orientations relative to one another. This procedure improves the surface of the finished paper and is called exchanging. The final stage in paper making is drying. The paper is hung, in groups of four or five sheets, over ropes in a special drying room until its moisture has almost completely evaporated.

Hand made papers are produced in small quantities, with local raw materials (often rare or scarce), and techniques (traditional, proprietary, rudimentary). Even where machine or chemical pulps are used, the unique style of forming gives a special flavour.

All hand made papers are unique in quality, texture and colour. Batch to batch acute variations gives a variegated character. Hand made papers have deckled edge on all the four sides, lesser thickness over the border regions, and multidirectional nonuniform grain structure. Hand made papers are less compact or dense. Hand made papers are naturally fluffy and absorbent unless heavily sized and severely calendered. Handmade paper is a reflection of its maker’s personality.

Hand made Papers are widely used for craft and decorative purposes. For writing or printing, however, it needs additional treatments following drying to make it less absorbent. The treatment consists of sizing the paper. Rough-textured papers are pressed lightly for a comparatively short period, and smooth-surfaced papers are pressed heavily for comparatively long periods.

Museum of Handmade Paper (Museo della Carta) View of Piazza del Duomo.

Museum of Handmade Paper (Museo della Carta) View of Piazza del Duomo.

The Museum of Handmade Paper, located in Mill Valley in the northern part of the modern town, celebrates the long-established paper making tradition in Amalfi. The town was one of the first centres of paper making in Europe, the skill having been acquired by the Amalfitans from the Arabs. The museum is housed in an ancient paper mill which was once owned by the Milano family, a family famous in Amalfi for its involvement in the production and manufacture of paper. In 1969 the building was converted into a museum as a result of the will of Nicholas Milano, the mill’s then owner. The museum contains the machinery and equipment (restored and fully functional) that was once used to manufacture paper by hand.

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MOULD MADE PAPER

Mould made papers are also produced on machines that are fairly automatized. The basic paper formation technique is like any hand made paper, but these are continuous one. A rotating mesh drum with part of the surface submerged in a pulp tub, draws in the pulp due to a partial vacuum. The drum continuously transfers the mass on the other side to felt-covered rollers which press the mass to drain out the excess water. The process is not only fast and continuous but provides a uniform output. Mould made papers have grain orientation along the length. Only two edges of a mould made paper are deckled. Mould made papers are fairly smooth, compact, of even thickness and uniform quality. Straw board sheets, rag papers, card papers, card boards, carton box papers, ledger paper, art work, graphics and lithography papers etc. are produced by this process. Most mould papers have one face with mesh impression while the other, face is comparatively smoother.

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MACHINE-MADE PAPER

Machine paper making is more complex, but basic processes are similar to hand-papermaking. Nominally paper machines can be divided into two main types: Cylinder machines and Fourdrinier’s machines.

Machine-made papers are produced in very large scale plants. Paper output is of very uniform quality, colour and thickness. Production of very wide (6 mts) and in large continuous lengths is possible. For the cheapest grades of paper, such as newsprint, ground-wood pulp alone is used. For better grades, chemical wood pulp, or a mixture of pulp and rag fibres, are employed. For the finest papers, such as the highest grades of writing papers, rag fibre alone is used.

Additives like colouring matter, sizing material such as rosin or glue, and fillers such as sulphate of lime or kaolin, which give added weight and body to the finished paper, are mixed into the pulp.

The face touching the wire mesh shows impression of wire compared to even face of the top side. In twin wire mesh processes two thin sheets are cast and their wire faces are joined together (usually without gums or sizing materials) to achieve both side smooth paper. Such sheets, because of natural lamination and disorientation of fibres show high strength, stability and tear resistance, as in currency notes.

Water-Mark

The dandy roll is a light unit lightly upon the wire and the surface of the sheet. Its function is to flatten the top surface of the sheet and improve the finish. Dandy rolls help create woven. laid and imprints names, insignia, or designs called watermarks. Paper watermarks have served to identify the makers of fine papers since the early day. A watermark is actually a thinner part of the sheet and is visible because of greater transmission of light.

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PAPER -part 2

by Gautam Shah

Earliest paper was made in China around 200 BC from a mass of entangled silk. Later (AD 105) it was produced using mulberry and other bast fibres, old rags, and hemp waste. The art of paper making was introduced in Japan in 610 AD, and into Central Asia about 750 AD. The first paper In Baghdad was made during 793, the golden age of Islamic culture,. Earliest paper in Europe was made in Spain, around 1036 AD., from linen and cotton rags. . By 14th C Several paper factories came up in Spain, Italy, France, and Germany. The demand for paper increased with the introduction of printing.

Till 18th C each region relied on local raw materials and so produced paper of local quality and style . By 19th C many pulping processes were innovated to overcome shortage of raw materials. The pulping processes related to separating fibres from wood by mechanical as well as chemical means.

Paper making

Nicolas-Louis Robert (1798) of France created first practical machines for paper manufacturing. Machine By 1875 papers created by machinery formed papers were used for new photoengraving process for printing halftones. Fourdrinier machines, (1884) produced long rolls of paper dried by suction, pressure, and heat. Pulp production by grinding wood, and chemical pulp processes offered cheaper raw materials.

Fourdrinier process

Earlier paper sheets were sized by a tedious impregnation process using animal glue or vegetable gums. But by 1800, paper sheets were sized with rosin and alum and bleached with chlorine.

Handmade Paper forming

Paper is mainly made from cellulosic fibres, derived from plant sources. The cell walls of all plants contain fibres of cellulose. It constitutes about one-third of the structural material of annual plants and about one-half that of perennial plants. The fibres depending on their origin have different types of cell structures and so provide unique character to the paper. Paper of some sort can be produced from almost natural plant, but qualitative requirements and economics of manufacturing, limit the sources of supply.

Pulp for Paper making

Cellulose for paper manufacturing is derived from many sources. Cellulose fibres have high strength and durability. They are readily wetted by water, exhibiting considerable swelling when saturated, and are hygroscopic. Even in the wet state, natural cellulose fibres show no loss in strength. Most plant materials also contain non-fibrous elements or cells. The non-fibrous cells are less desirable for the paper-making, than fibres, but mixed with fibre, are of some value such as the filling material in the paper sheet. It is the combination of these qualities with strength and flexibility that makes cellulose of unique value for paper manufacturing.

Fibre sources: Major sources of cellulose for paper manufacturing is wood. Cotton is the next important source of cellulose for paper making. Cotton fibres are used in the form of lints (seed hair left behind after ginning), staples, waste yarn and threads and rags. Lints require no processing, staples need length shortening, but yarns, threads and rags need undoing of all mechanical processes such as spinning and weaving. Cotton fibres are used where maximum strength, durability, and permanence, as well as fine formation, colour, texture, and feel, are required. These properties are attributed to the greater fineness, length, and purity of rag fibre as compared with most wood pulp. Rag papers are used extensively for bank note and security certificates, life insurance policies and legal documents, for which permanence is of prime importance, technical papers, such as tracing paper, vellums, and reproduction papers, high-grade bond letterheads, which must be impressive in appearance and texture, lightweight specialities such as cigarette, carbon, and Bible papers, and high-grade stationery, in which beauty, softness, and fine texture are desired. Khadi paper is an example of high rag content paper.

Linen, Jute, Hemp, various type of grass, bamboo, cane (rattan), paddy (rice) straw, banana leaf, sugar cane waste (bagasse), are some of the other sources for cellulose.

The cut and cleaned rags are cooked (to remove natural waxes, fillers, oils, and grease) in large cylindrical or spherical boilers. About three parts of cooking liquor, a dilute alkaline solution of lime and soda ash or caustic soda combined with wetting agents or detergents, is used with each part of rags. Steam is admitted to the boiler under pressure, and the contents are cooked for three to ten hours. Once cooked, the rags are washed, then mechanically beaten. The beating shortens the fibre, increases the swelling action of water to produce a softened and plastic fibre, and fibrillates or frays the fibre to increase its surface area. All of these actions contribute to better formation of the paper sheet, closer contact and inter-fibre bonding that gives the paper strength and coherence.

Waste-paper is a major source for cellulose. By recycling the waste-paper the dependency for virgin fibre is reduced and the problem of solid waste disposal is minimized. However, the difficulties like, gathering waste-paper from scattered sources, sorting mixed papers, and recovering the fibre from many types of coated and treated papers, make it a very complex problem. Paper treatments such as asphalt, synthetic adhesives, metal foils, plastic and cellulose-derivative films and coatings, printing inks, etc. pose acute problems in reuse of paper wastes.

Waste-paper is of four main categories: High-grade, old corrugated boxes, printed news papers, and mixed paper. High-grades and corrugated stocks originate mainly in mercantile and industrial establishments. White paper wastes accumulate in paper conversion units and printing plants. Magazine stock comes from news-stand returns, but some comes from homes. Mixed papers come from collectors. There are two distinct types of paper recovery systems: 1. recovery based upon de-inking and intended for printing-grade or other white papers, and 2. recovery without de-inking, intended for box-boards and coarse papers. Caustic soda, soda ash, silicate of soda, phosphates, and surfactant are used to remove the inks.

Natural fibres other than wood: Alternative sources for paper pulp have been in use even before wood pulp was available. Cereal straws, plant stems, paddy husk, grasses like esparto, bagasses (sugar cane), etc. are used in many parts of the world, that are deficient in forests and where such products are abundantly available. Non-woody plant stems differ from wood, as these contain less total cellulose, less lignin, and more of other materials. Papers made from these pulps without an admixture of other fibre tend to be dense and stiff, with low tear resistance and low opacity.

Flax, Hemp, Jute. Kenaf have been highly prized because of the strength and durability it imparts to such products as tags, abrasive paper (sandpaper), cover stock, and other heavy-duty paper. It is also used for duplicating and manifold paper, in which extremely light weight paper must have exceptional strength. Flax is grown expressly for high-grade cigarette paper.

Synthetic fibres: Synthetic or man-made fibres provide certain advantage when compared to plant based materials for paper pulp. Natural cellulose fibres vary considerably in size and shape, whereas synthetic fibres can be made uniform and of selected length and diameter. Long fibres, for example, are necessary in producing strong, durable papers. There are limitations, however, to the length of synthetic fibres that may be formed from suspension in water because of their tendency to tangle and to rope together. Even so, papers have been made experimentally with fibres several times longer than those typical of wood pulp, these papers have improved strength and softness properties. Natural cellulose fibres have limited resistance to chemical attack and exposure to heat. For such purposes synthetic fibre papers can be made resistant to strong acids, for example in chemical filtration. Paper can even be made from glass fibre, and such paper has great resistance to both the heat and chemicals. Natural fibres swell when beaten in water and cement together as they dry, synthetic fibres must be bonded by the addition of an adhesive, requiring an additional manufacturing step. Synthetic fibres are not affected by changes in moisture and produce dimensional ly stable papers.

Synthetic fibre felts (non-woven) are very similar to paper in construction. Yarn staples, carding waste, and filament cuts often re-carded, i.e., separated, combed and pressed to form a uniform, lightweight, and fragile web. This web, felt or the non woven-blankets if assimilated with heat or adhesive, a product similar to paper results.

Pulp is produced by both mechanical and chemical (alkali & acid type) processes. Wood is debarked cut into pieces, pulverized and pulped with water as the main suspending agent. A mechanical pulp sometimes contains several impurities like lignin, woody matter etc. Mechanical processes reduce the fiber length due to heavy handling of the mass. On the other hand chemical processes being less severe, do not reduce the fiber length. Removal of impurities’ is very good. However, adjustment of PH level is sometimes a problem. Chemical pulps are sometimes called wood free pulps, because there is a substantial removal of lignin and other woody matter. During pulping the mass is cleaned and bleached.

Mechanical or ground-wood pulp is made by subjecting wood to an abrading action, either by pressing the wood against revolving grinding stones or by passing the chips through a mill. The pulp stock flows from the grinder to a series of riffles and screens, which separate the heavy foreign material and pieces of non- fiber wood (shives), knots, bark, and the like. The wood fibres are separated. In ground wood pulp, the fibres are fragmented, and there is considerable debris (fines). Ground wood pulps contain all the chemical constituents of wood, including lignin, hemi-cellulose, resin, and various colouring materials. This debris on exposure to light and heat and after ageing, cause discolouration (yellowing) of paper. Ground wood pulps are not very white, so are often bleached with peroxide or hydro sulphite to improve the whiteness, yet it does not equal to whiteness of pure cellulose. Ground wood pulp fibres are relatively short and have only a moderate ability to bond each other, so papers made from such raw materials have low strength. However, papers containing ground wood have good opacity, high bulk and good printing qualities.

Chemical wood pulp is made by cooking wood chips with chemical solutions in digester operated at elevated temperature and pressure. The chemicals used for two prime purposes 1. To make the lignin of wood soluble, and 2 for purification and bleaching. Paper produced by the kraft process is particularly strong and durable. Chemical wood pulp that is purified both by bleaching and by alkaline extraction is called an alpha or dissolving pulp, and is used for speciality papers.

Semi chemical pulp is made by treating wood chips with sulphite or alkali in amounts and under conditions that soften the lignin, but dissolve only part of it. The softened chips are then de-fibred. The chips are steeped and impregnated with inorganic chemical solutions similar to those used for full chemical pulping, but in smaller amounts and with less severe condition.

The high fiber yield pulps are usually termed chem-mechanical pulps. The semi chemical-pulps have chemical and strength properties intermediate between softwood, ground wood, and full chemical pulps. These are used in a wide range of papers and boards. The major tonnage of semi chemical pulps goes into the light board (termed corrugating medium), which is fluted to serve as the interior layer of corrugated box board in heavy-duty containers. Stiffness and adequate strength are the important properties. Semi chemical pulp is used in many low-cost printing papers.

Various agents are added to paper pulp to enhance or to modify the bonding and coherence between fibres. To increase the dry strength of paper, the materials most commonly used are starch, poly acrylamide resins, and natural gums such as locust bean gum and guar gum.

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PAPER -part 1

By Gautam Shah ➔

Paper for Writing by Johannes Vermeer

Paper has been the prime medium for expression and communication. In addition, paper and paper-board products provide materials for hundreds of other uses, such as wrapping, packaging, towelling, insulating and photography. Paper is also used in several interior decorative and functional products.

Paper is a thin flexible sheet material composed of naturally originating cellulose fibres, interlaced into a compact web. The web is formed by deposition of cellulosic pulp -an aqueous suspension of cellulose fibres. Paper has also been defined as a matted or felted sheet formed of cellulosic pulp on a lattice from a water-suspended phase.

The word paper is derived from the name of the reedy plant papyrus, which grows abundantly along the Nile river in Egypt. In ancient times, the fibrous layers within the stem of this plant were removed, placed side by side, and topped with another set crossed at right angles. The layered sheet so composed was dampened and pressed. On drying the layers with the help of glue like sap of the plant that helps in cementing.

First true paper through pulp process, as we know today, was made in China. It was a substitute product for Silk for many uses.

Paper manufacturing sequence

In ancient times writing media of many types have been used, such as Papyrus, barks of trees, parchment (lamb or sheep skin), Vellum (calf skin), Gevil (animal hides with shaved hair), Wax coated tablets, Clay tablets, Bhoj and palm leaves. Other writing materials included ceramics, metal sheets and stone faces.

Bamboo strips for Writing – China

Tree leaf as writing media

An Old map on Vellum

Parchment making

Clay Tablet

Foldable wax coated – rewritable writing tablet of Romans

Paper is a material with many different forms, qualities and properties. The manifold varieties of paper are achieved by selection of the fibre material, its subsequent treatments, additives employed and the way the paper sheet is cast or formed, consolidated and dried. In addition paper is modified by several subsequent conversion processes.

Paper as a material is available with many different surface qualities and constructions. It can be rough, smooth, greaseproof, water absorbent, water repellent or resistant, soft as cotton, stiff as board, heat resistant, fireproof, combustible, chemically resistant opaque, translucent, transparent, coloured, glossy, dull, strong, weak, tear-able, non-tear-able, light heavy, pulp-able cellular, waxed, sanded, embossed hinged corrugated, easily folded and pierced, coarse, fine or flocked.

Paper is used for writing, printing, drawing, painting signs and images. Paper is used for wrapping, filtering, absorbing, insulating, protecting (Thai umbrellas), cleaning, mopping, polishing, buffing, toys and product forming, mould making, engraving, etching, embossing, Medicare dressing, garment making, and for glazing (Shoji for windows and Fusuma for room dividers).

Paper is manufactured from material resources that can be regenerated and the product is a recyclable material. If we can replace trees as the source for raw material, it can be a perfectly eco-friendly or sustainable product.

Structure of paper differs from other sheet materials:

1. Paper unlike plastic films and metal films are fibrous.

2. Paper is composed of single short fibres, arranged largely randomly instead of a regular array as is the case with woven fabrics.

3 Unlike cloth, felt or leather it is a laminar product, that is each fiber is disposed mainly in the plane of a sheet.

Paper, however, resembles other sheet materials as its structure is anisotropic in its plane and most of the fibres are oriented along the grain or the machine direction.

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Next in series >> PAPER -part 2 History & Manufacturing processes / PAPER -part 3 Products and Conversion processes.

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HAMMERS

Post by –Gautam Shah

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A hand tool is an instrument of various forms and purposes, traditionally operated by the muscular power of the user. Major section of hand Tools are of Percussive variety. These tools are used to deliver blows such as axes, adz, and hammers, etc. Other varieties include cutting, drilling, and abrading tools such as the knife, awl, drill, saw, file, chisel, and plane.

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Dent repair tools Image from Photobucket.com/user/afazz65/media/tools/drawer18

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Carvers hammers of wood > Flickr image by Danny Ayers

Percussive tools deliver concentrated blows or impact in swift motion and so are also called dynamic tools. The prime tools in this category are the Axe and Hammer. An axe is a cutting tool, but it has been used for striking, so a percussive tool.

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Ancient tied Stone head hammers

HAMMERING TOOLS

A hammer is a striking tool also known as a pounder, beetle, mallet, maul, pestle, sledge, etc. There are many trade specific hammers, like, the carpenter’s claw type, smith’s riveting, boiler-maker’s, bricklayer’s, blacksmith’s, machinist’s ball peen and cross peen, goldsmiths’, smith’s stone (or spalling), prospecting, and tack hammers.

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Wood Hammer > Wikipedia image by Johan (GFDL)

Each hammer has a distinctive form, with minor variations in terms of weight, length and angle of the handle, and the profile of the face. A pounder, or hammer stone, was the second tool, after the axe to have a handle, marking a great technological advance. A long handle, is needed for striking effect such as in a tool used for light blows. It makes the tool easier to control, and generally reduces operators’ fatigue.

Splitting maul

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Stockhammer > Wikipedia Image by Reiner Flassig

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Forge trip hammer > wikipedia image by William F. Durfee

Club like pounders or mallet, with a handle of the same as well as different materials are widely used. The hammer as a tool, for nailing, riveting, and smiting, originated in the Metal Age. For beating lumps of metal into strips and sheet, heavy and compact hammers with flat faces are needed, whereas lighter ones are more suited to riveting and driving nails and wooden pegs.

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Old Pick Hammer > Wikipedia image by Vassil

Hammers with dual heads are in use since Roman age. Hammers with dual heads include, clawed hammers for pulling out nails, hammers with a chisel or pointed ends to dig out shafts, toothed edges to smoothen the stone surfaces. Other special forms of the peen (-the end opposite the flat face) like hemispherical, round edged, and wedge like shapes helped the metalworker stretch and bend metal or the mason to chip or break stone or bricks.

Hammer for upholstery work

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from a catalogue of suppliers to watchmakers and jewelers

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Ritual hammers from Early Bronze age to II Mil BC

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Dressing Hammer > Wikipedia image by Rasbak

A file maker’s hammer has two chisel-like heads, to score flat pieces of lead (file blanks) that are subsequently hardened by heating and quenching. Heavy hammers are used as part of power tools, and largest are the pile drives for foundation work. Trip-hammers are gravity impulse based but steam hammers use, besides gravity a downward thrust from a steam-pushed piston.

Pneumatic hammers are driven by air and include the hammer drill used for work on rock and concrete. The rivetting hammer is used in steel construction for flattening rivet heads over girders and plates.

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Pounding Rice Cake in Korea > Image by Cornell University @ Flickr Commons

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Making Rice Cakes > Flickr Image by A. Davey

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OTHER TYPES of DOORS

By Gautam Shah  

cooker

Pressure Cookers with Inner and Outer Lid sealing

PRESSURE COOKER SHUTTERS

These are pressure doors or plug doors. As the pressure inside increases the shutter leaf presses itself harder on the outer or inner seams. The bulge (convex) shape of the lid adds to the surface area for greater efficiency of sealing. A well-designed plug door relies only on the strength of the wall around (forming the seams) it. Plug doors like situations also occur on high altitude flying passenger air-crafts. Due to the higher air pressure within the aircraft cabin than of the surrounding atmosphere the door seals itself. This prevents the opening of a plug door on a pressurized aircraft. However, at lower altitudes or on landing the decompression, allows a door to be opened. Rapid Transit Series buses feature front and rear plug doors.

Hatch door with Hinge mechanism

HATCHES

Front loading Washing Machine Hatch Door

These are doors for entry into large tanks, reservoirs, boats, submarines, car roofs, washing machines and space vehicles. These doors like openings are very small size, just circumference of a person, and are placed in a wall or roof (though at places the wall or roof definitions are irrelevant). The door or the lid is either hinged one or is a free unit. The hatches have a glass lid, glass a view window, but all in bulged form. The hatches are required to fit snugly so have air-water tight gasket lining. The door closing is secured through multiple snap-clamps or bolts. The opening and shutting are often triggered by the pressure conditions on either side of the lid. The hatches in walls are slightly raised, whereas the in floors these have a marked and raised perimeter or are fitted in level with the surrounding structure. Hatch doors are designed as less frequently used opening system, but snug-closing is important. Ship and aircraft windows which are fixed and are round edged openings are also called hatch openings. Automobiles also have a roof level hatch openings.

Space Module Hatch Door

Submarine Hatch Door

CHEMICAL REACTION VESSELS SHUTTERS

These are similar to hatched openings, but could be as large as the mouth of the reaction vessel, or of functional size that allows addition of raw materials or drawing out a batch sample. These shutters are rim over the rim fitting type or flat-edge fitting systems where no internal pressure generation occurs. Otherwise, for pressure reaction vessels, the shutter systems are similar to domestic kitchen pressure cookers.

Chemical reaction vessels

NON-PLUG DOORS

A paint tin lid is a common example of a non plug door. It relies on the wedge shape of the seam edge. Canvas sheets in artists’ frames are held by clamps.

Paint Tin Lid

VALVES

Valves have a closing diaphragm or a plunger to seal an opening and thereby cut the flow. Butter fly valves have a central pivoting diaphragm similar to wings of a butterfly. Ball valves have a ball which gets displaced by the pressure of liquid or gas, but shuts the opening by falling down due to gravity, and thereby prevent any floe in reverse direction.

Butterfly Valve

FLY DOORS OR CAMERA SHUTTERS

Old style Camera shutters have multiple flaps, which is pin pivoted at the outer edge, whereas the inner edges overlap. The flaps open and close very simultaneously and quickly by a rotating mechanism that actuates the outer edge of the pivot. The inner edges form a polygon or nearly a circle, thus giving a smooth edge to the picture being shot. New technology cameras have CCD devices which are activated by an electrical impulse.

Camera Shutter

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TORAN

Postby Gautam Shah

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GC-X1E Image

Toran is a decorative bridging element between two posts, columns, or door sides. Torans are permanent (built-in) decorative treatments as well as seasonal or festival-days decorations. Torans are synonymous with doors, Gates and points of entrance. A series of torans marks a passageway to an entrance. Toran also denotes beginning of a precinct.

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Torans are a sign of welcome and honour for the bridegroom and a marriage procession arriving to a bride’s home (or a place of marriage), victors coming home, a deity being brought to home, or family member returning from a long-lasting voyage. A bridegroom has to wait under the toran of the gate till formally invited inside. Army platoons, returning from a remarkable venture touch their spearheads or flag-tips to the Toran.

Toran Jain Architecture Ranakpur, Rajasthan, India

Torans are hung over town or fort gates to ward off the evil or diseases. Shopkeepers in India hang seven green chilies and a lemon through a black thread to ward off evil effects of Saturn and generate good business. These hangings are changed nominally every Saturday, or more frequently during lean periods.

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Torans touch the head part of an opening as a decoration, but a doorway Toran that touches or swipes the head blesses every person passing under it, showering with an abundance of love, prosperity, health and happiness. The Toran is very often a part of a bride’s trousseau as it brings prosperity and well being for the groom and his family.

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Torans symbolically mark the alliance or dominance. No political gathering is without it. Toran hanging is beginning of festivity. Marriage, birth, child naming ceremony, social or political gatherings, all start with a Toran. Several torans, criss crossing an open ground create effect of an arena.

Highly polished thin Bronze metal sheets were hung high masts, on Eastern front of the ancient Egyptian temples, to glow with the first rays of rising Sun denoting arrival of Ra -the Sun God.

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The Torii Gate of Japan is symbolically very close to Gates of Sanchi Stupa, India. Both represent a bent bridging line (flexibility of string) between two poles, the essence of a Toran. Similarly the ‘Pai Lous’, or Gateways of Chinese architecture have features of Toran.

Sanchi Stupa, Buddhist Toran Gate, India

Chinese Pai Louis Gate -Toran Architecture

VARIETIES of TORAN

Home Door Toran for Celebration

Earliest Torans were Buntings with objects hanging from a rope or string. The flexible string made the objects mobile and vibrant. The softness of the string and the dynamic form of the hangings are the essence of a Toran.

Buntings

● Torans are made of perishable materials like flowers, (marigolds, roses, jasmine) fruits (bananas, pineapples and coconut), vegetables, green or dried leaves (Neem, Mango or Asopalav -Polyalthia longifolia, false ashok) of trees.

Lantern Toran

● Torans of Soft materials like pieces of ropes and fabrics (embroidered, patch-worked, printed and painted), paper (cut pieces, ribbons and formed into floral or lantern shapes).

A Fabric Embroidered Toran, Kutchh region, Gujarat, India

 ● Torans are made of lasting materials, glass beads and thin metal sheets and foils and plastic extruded shapes.

Glass Bead Toran 1 Deesa, Gujarat India

Glass Bead Toran 1 Deesa, Gujarat India

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Glass Bead Toran 2 Deesa, Gujarat India

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Glass Bead Toran 3 Deesa, Gujarat India

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Glass Bead Toran 4 Deesa, Gujarat India

● Architectural Torans are made of carved stones and wood. These built torans work as a bracket reducing the span of door heads. These may take the form of inclined support or corbelled-arch or partial support bracket.

Architectural Toran Modhera Sun Temple, Gujarat, India

 Chitra torans are drawn versions over top sections of the real or imaginary door, gates and also walls.

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Makara or Pātrā Toran (made of terracotta, brass and copper vessels are used on Temple entrances, town gates and in public squares.

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Illuminated Torans is a modern version of Toran. These could be as a series of lights, programmed to various types sequences, Neon lights, LEDs and LCDs with colour dynamic and variegated colour combinations. Other Torans in this category include Pyro Fire-works.

Fire Works

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