ABRADING TOOLS

Post -by Gautam Shah

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Traditional street side grinding of knives and scissors

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Metal abrading grinder

The first abrading tools were rough stones and hard grained abrasive sands. Tough fibres like asbestos, wool, and coir were also used for buffing purposes. Today sandpapers in sheet, stripes and tape forms are available with paper and cloth backing and bonded with water-based gums and synthetic resins. Carborundum and other man-made ceramic granules are embedded or cast in various base materials and shaped as discs, wheels, cones, rings, etc. for use with various machines. Such abrading tools are also used for drilling, edge dressing, tunneling, boring, etc.

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Abrading stones are used to grind, de-husk and surface polish the food grains, nuts and seeds. This is done by pounding or by milling between stones. Nails, Screws, Nut-bolts, Toffees and sugar coated pills are rotated in drums to polish the surface.

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Automobile and other lacquer finishes are buff-polished with very fine abrading media mixed with wax and silicon oil-based rubbing compounds. Abrading materials are also included in soft articles used in household utensil cleansers and jewellers polish to the hardest known material, the diamond. Leather, Jute, Linen, Chamois and may other materials with harder fibers are used for rubbing and polishing. Abrasives are used in the form of tumbling and vibratory mass-finishing media as for polishing for nails, sandblasting, flour mill stones, ball mills. Spectacle lenses and telescope lenses are ground with a abrading and then polishing media.

Hubble Telescope lens grinding

Abrasive materials and tools can cut through hardest materials at a faster speed than metal saws, while generating less heat and providing smoother cut face. New hard alloys and ceramics can only be cut by abrasives. Granite, marble, slate, and highly vitrified tiles are cut to size with diamond abrasive wheels. Grooves for expansion joints in runways and roads, holes in RCC structures are made by metal blades with embedded diamond abrasives. Metal components are cleaned by grinding tools of wire or hair wheels or by sand blasting.

Files of Different grains

Rasps

FILES: Files are abrading tools. Files are of many different cross sections, lengths, notch configurations and the coarseness of the cut (density -teeth per area). A file could be very thin, almost like a knife with a serrated cutting edge, to a wide chequered figured plate. The most common sections are rectangular, triangular, round and half round. Most files have reduced size of section at their tail end. There are three tooth forms: The single-cut file has rows of parallel teeth that cut diagonally across the working surfaces. The double-cut file has rows of teeth crossing each other. Rasp teeth are disconnected round top notches. Rasp files, or rasps, are usually very coarse and are used primarily on wood and also soft materials like leather, aluminium, lead, etc. Files are used for many different purposes: to smoothen nails, cut injection vials of glass, removing human skin blemishes and birthmarks, for shaping bones during plastic surgery, removing spots and discolourations from suede fabrics, and for levelling teeth.

Grinder brush of Metal or Hair

Milling Machine Control Joinery Industry Carpenter

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EARLY PROGRAMMING LANGUAGES

by Gautam Shah  ➔

Animated Clocks

A set of commands to control a series of actions by a human is a very intelligent and natural action. But to translate, that for a machine, is the primary programming language. Here the predictable sequences are linked in such a way that follow-up actions are dependent on the preceding process. First programmed tools were watches, animated clocks, toys and music players. These mostly worked on sprocket wheels, where an odd teeth initiated an action. The programmed tools worked on mechanically powered sprockets, so were mostly fixed time apparatus. There was no human intervention in its operations except for powering the movement.

Musical Cylinders

First programming languages were process oriented languages, consisting of commands to control a machine. The commands were executed by pressing levers, marked buttons or switches. Such processes were often chained to one another for sequential activation, a rudimentary form of automation.

Winding Clock

In the process languages such as Kashmir carpet weavers’ manuals, the commands were recite-able names in ordinary language. Often strings of words were used to not only name the command but also its purpose. However, in Jacquard looms, piano playing scrolls and cuckoo clocks, the commands were punched holes or slots. These were machine-readable languages, and used a very small vocabulary. The dash-dot language of earlier wireless communication is an example of such an economical expression. Later binary, hex and many other types of number formats were used.

Jacquard Card Punching machine

Artisans who weave the carpets use a unique code language called ‘Talim’ devised by early Kashmiri for the pattern of knotting handmade carpets. The language was coded with abstract signs.

Command triggering which was initially automated through sequencing and looping also had time delay mechanisms. The time delay mechanisms were made first by mechanical actions, and later through electric and electronics devices. Internally generated or supplied information of feedback, feed forward and other parametric definitions provided the specific conditions for initiation, continuation and termination of the process.

As the processes became long and complex it was recognised that certain independent sub-processes could be handled in a parallel mode. For linear processes the command structure -algorithms are easy to implement, but for non-linear processes (branched, looped), the commands are interdependent, requiring many complicated control-check systems.

  • Algorithms: A machine works on two basic inputs: the raw materials (or data) and instructions or activation commands (to initiate or terminate a process). An algorithm is an exact formulation of method for accomplishing a task. However, not all statements or documents of instructions have such logical order that can be seen as an algorithm. Algorithms are a must for machine processing of information. An algorithm is an aid or process analysis that ultimately is transformed through coding into a machine-language.
  • The key idea behind Jacquard’s loom was to control the action of the weaving process by interfacing the behaviour of the loom to an encoding of the pattern to be reproduced. In order to do this Jacquard arranged for the pattern to be depicted as a group of holes `punched’ into a sequence of pasteboard card. Each card contained the same number of rows and columns, and the presence or absence of a hole was detected mechanically and used to determine the actions of the loom. By combining a `tape’ of cards together the Jacquard loom was able to weave (and reproduce) patterns of great complexity, e.g. a surviving example is a black and white silk portrait of Jacquard woven under the control of a 10,000 card `programme’.

Creating a Carpet language

 

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COMPOSITION of a COATING

by Gautam Shah ➔

Coatings are thin surfacing. A coating comes into being mainly through a phase-change of a material. At pre-application-stage a coating material is in various phases such as solid, liquid or vapour, or a combination thereof like: suspension, solution, dispersion, emulsion, thermoplastic compound, thixotropic compound, etc. During application it changes to a Liquid phase, but once applied, it settles down to a heavier phase, usually (but not necessarily) a Solid phase.

Coatings are not exactly considered to be adhered-finishes, because the coating film is formed and (mainly) bonded through a lower to higher phase conversion process.

Coating is a thin Surface Finishing Technique. A coating system has Four main components.

1. Film forming substances

2. Solvents and Diluents

3. Pigments and Extenders

4. Other additives

Film forming substances are the prime materials of a coating system. Even if other components are not present, a coating (Clear coating) can still be created. Most of the film forming substances are in liquid form or convert to a liquid phase just prior to application. Film forming substances provide a film that binds all the ingredients, and also develop inter-facial adhesion between the coating and the substrate.

Solvents and diluents, impart solubility to specific film forming substances, allow dispersion and adjust the viscosity.

Pigments are chief colourants to coloured coatings. In some clear as well as coloured coatings, Dyes (dispersed or dissolved) are added to provide specific tinge (staining) to the coatings. Other colourants include opacifiers, whitening agents, fluorescent phosphorescence agents. These besides providing colour, impart transparency translucency, opacity, fluorescence, phosphorescent and luminance to the film. Extenders or fillers are low refractivity materials, usually white, but not necessarily. These are added to provide bulk to the coating, economise the use of pigments.

Additives help in manufacturing, storing, applying, drying and maintenance of a coating. These include surfactant, anti skin agents, wrinkle agents, dryers (metallic compounds that helps in polymerization of resins), thixotropic agents, foaming and de-foaming agents, catalysts, odour suppressants, mildewcide, insecticide, fungicide, plasticizers, anti setting agents, etc.

A clear coating (often called Varnish) has no pigments or extenders. For a specific tinge (transparent staining) dyes or very low proportion of pigments are used.

Surface treatments: Coatings are generally capable of forming a film on the relevant surface. But to receive a coating, the surface may require some modification or treatment. Surface treatments form a very important section of coating technology. Surface treatments are specific for the surface to be coated, such as cleaning, roughening, smoothening, etching, etc., or moisture proofing, rust inhibiting, barriers, static arresters, etc. Other surface treatments are designed to facilitate the application or deposition of the surface forming component and its setting or drying.

Coatings are deposited on objects by many different techniques and in variety of conditions. Common coatings are applied at normal environmental conditions. However, high end coatings require conditions that are usually unavailable at construction sites such as exact environment and controlled application, drying and handling techniques.

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GRISAILLE -monochrome form of presentation

Postby Gautam Shah

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In the later Middle Ages a new style, purged of colours, emerged to create artworks like painting, glass compositions and fabric arts etc. Grisaille painting is a technique where an image is executed entirely in shades of gray and modelled for the illusive effect of relief sculpture. The use of colour was a gray-scale palette like black, grey or single tones. This emerged perhaps as metaphorical simplicity for religious modesty or as a dissolution of the distinction between sculpture and drawn arts. The chosen palette merged the three-dimensional sculpture or built-form, and the two-dimensional drawings.

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The Grisaille sobered up the art, sculpture and architecture scene. In architecture, the clerestory windows of Gothic cathedrals replaced the saturated coloured glasses with patterned grisaille glass. This created interior architecture that was more honest to the form than the effect. It also devalued the story telling-board function of the windows.

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Grisaille style of monochrome or single hue presentations, encouraged the exploitation inherent patterns and textures of the architectural surfaces. The art of creating depth or its illusion through form-shape, shadows, silhouettes and forward-backward was re-explored.

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In French, Grisaille has also come to mean any painting technique in which translucent oil colours are laid over a monotone under-painting.

Grisaille (French: gris =grey), is an artwork form where Grey and its various tones are used to create sculptural effect in paintings. It is largely a monochrome form of presentation, though few other colours are also used. Frescoes with Brown tones have been called Brunaille, and with Green tones Verdaille.

Grisaille as technique is similar to Chiaroscuro. It uses shades as one basic tone to present many materials. It is also similar to charcoal or sinopia used for preparing a sketch, understudy, or prefigure outline.

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Grisaille form could be a painting or glass-art or an understudy for a painting. ‘Rubens and his school sometimes use monochrome techniques in sketching compositions for engravers.’ Grisaille was often used, to see the validity of a proposed sculptural composition. It was used to imitate classical sculptures in wall and ceiling decorations. In French, Grisaille has also come to mean any painting technique in which translucent oil colours are laid over a monotone under-painting.

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This art-form was preferred for being faster and cheaper. Sometimes, however, it was intentionally used for being less committal and also for its aesthetical beauty. Grisaille art-form was used by glass painters for colouring in place of stained glass or pot glass. Grisaille windows were popular because the monochromatic panes of white glass with black or brown painted outlines offered a very sober and brighter interior environment. It saved money, and worked well as a replacement for stained glass or leaded windows.

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PAPER FINISHING and CONVERTING

Postby Gautam Shah

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Paper Finishing Operations account for 20% or more of the cost of paper (raw cellulose to reusable paper conversion). A finishing process improvises the quality, or may give birth to a very different product. Many of the finishing processes are carried out at a different plants’ locations, along with size conversion. Such plant processes are sometimes called off machine processes, because these are carried out, away from the paper production plant.

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Showroom of traditional Laotian craft and hand made paper > Flickr image by shankar s.

Papers need to be conditioned before and after finishing materials and techniques are applied. The object of conditioning is to eliminate some of the undesirable side effects that have been acquired during paper making process. It is a maturing process having two principal objects.

To rid the paper of stresses that may have been incurred during the paper making process, and that may otherwise be released during subsequent treatments.

To stabilize the moisture content evenly across the width and along the machine direction, to a desired level.

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Hand pressed papers’ stacks Seoul Korea, Wikipedia image +Flickr image by jared

● Curls are caused by the different rates of shrinkage or expansion of the two faces of the paper sheet. Curls arise from the web due to differences in fiber orientation between the top and bottom of the sheet, and also due the difference in the distribution of fines.

● Cockle is caused by differences in internal stresses in a sheet. Generally this is the result of unequal drying, due to localized variations in moisture and substance contents.

Kites Festival Gujarat India

There are TWO distinct types of paper conversion. One is referred to as wet converting, in which paper in roll form is coated, impregnated, and laminated with various applied materials to improve properties for special purposes. The second is referred to as dry converting, in which paper in roll form is converted into such items as bags, envelopes, boxes, small rolls, and packs of sheets.

Calendaring is a process of pressing between two smooth chilled rolls, or plates to produce a smooth-finish, known as machine finish. Calendaring, also compacts the paper-mass and create a glossy finish or desired texture on the surface. Special papers are given additional treatments. Paper is subjected to a further calendaring process -super-calendaring, under great pressure between metal and paper-covered rolls. Coated paper, such as that used for fine half-tone reproduction, is sized with clay or glue and calendared.

Multi-ply corrugated Paper Box

 PAPER TREATMENTS

Papers are coated by many different materials and through equally varied techniques. Lacquer or polymer coated papers are used where moisture resistance is required. Plastic papers have coatings or layers of pre formed polymeric films. These are generally moisture and dirt resistant, and are used for packaging, children’s books etc. Wax coated papers are used for disposable dishes and ice-cream containers. Carbon papers have a coating of wax impregnated with carbon black pigment. Thermal papers have static properties suitable for achieving a printout in xerox or fax like machines. Cheque or security papers have special starch coatings, which can be seen in UV light. Electrical winding papers are coated with phenol formaldehyde varnish. Laminates have printed design papers sandwiched between a paper substrate (layers of papers bonded to gather with phenolic compounds) and film or coating of melamine compound. Blue print papers have ferric azo compounds that are light sensitive but can be stabilized with ammonia. Photographic papers are super quality, ultra bleached, super calendared and low level PH, papers, coated with silver compounds.

Tetra pack of Laminated papers

Papers have been coated to improve the surface for better reproduction of printed images for over 100 years. The introduction of half-tone and colour printing has created a strong demand for coated paper. Coatings are applied to paper to achieve uniformity of surface for printing inks, lacquers, and the like, to obtain printed images without blemishes visible to the eye. Coated papers help to enhance opacity, glossy to matt finishes, and to achieve economy in the weight and composition of base paper stock by the upgrading effect of coating.

Laminated Cards

Co-extrusion-coating process, is a relatively new development in the application of functional coatings. It is used to apply polyethylene and such extrudable thermo-plastic materials to paper, or paper boards. Polyethylene resin has ideal properties for use with packaging paper, being waterproof, resistant to grease, water vapour, and gases, highly stable, flexible in heat sealing, and free from odour and toxicity. The hot extruded film is stretched and combined with paper between a pair of rolls, one of which is rubber-covered pressure roll and the other a water-cooled, chromium-plated steel roll. The amalgamation between the plastic film and the paper is perfect and a permanent bond is created.

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MOVING out of the BUILT FORM

post- by Gautam Shah

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Built form designing begins with a neatly defined geometric shape, but it evolves into a very complex form. A complex form becomes an architectural adventure to gain new spaces, experiences and uses. The basic form was modulated, followed by its vocabulary and treatment and ornamentation. In few years time the original entity is so morphed that the new entity becomes the defacto form or solution.

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There are several ways this is done:

1. Modulate the surface from a plane to singly and doubly a curved entity.

2. Introduce curving lines in parallel or perpendicular to gravity planes or askew planes.

3. The basic unitary geometric shape is recast into a formation of several volumetrically modulated entities.

4. Taper or enlarge the form in upward or downward directions.

5. Trim or Shape the edges and corners.

6. Transgress the form inward and outward, with voids and solids.

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Building forms are transgressed to the exterior for many different purposes. The prime purpose is to enlarge the interior space, to open out the omni present sense of enclosure, to bring in the lightness of the exterior, to stretch the internal and external surface area to enhance the built mass, to add a textural entity over the surface, to add thresholds (in-between) spaces and to sideways view, aeration or sunlight facilities.

Corner projecting oriel

■ ORIEL: Oriel windows are a form of polygonal bay windows. Oriel windows, have a larger perimeter then a normal flat window, and so allow wider view of the outside. Oriel windows increase the floor space without increasing the footprint (extent) of the building. Oriel windows are usually placed on the upper floors of the building, but siting on ground floors is not common. The windows are projected bays, supported off the base-wall by columns, piers, corbels or brackets.

Oriel window

Such windows have of many forms: start from the floor level, seat level or mid body level, the head-side of the projected gap terminates at lower, at human head level or reach to the ceiling level. Some oriels are partly or wholly glazed. Oriel windows like latticed forms are found in Indian Zarokha and in mid East or Arab architecture as Mashrabiya. In both the cases the lattice reduces the glare and provides privacy. Zarokha is more commonly made of stone work, and Mashrabiya have carved wood latticework and often stained glass. Oriels are also found extremely dark streets. Oriel windows were also placed over gateways or entrances to manor houses and public buildings.

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■ BAY WINDOWS: A bay window is an exterior projection of room space, forming a bay of square or polygonal shape. The round shaped (segmental) windows are called bow-windows. Bay windows became popular with Victorian architecture (1870’s). A typical bay window consists of three windows, the middle unit is parallel to the house and adjoining two units are set at 30 to 45 degree angles. Bay windows are created: to increase the illumination, provide a wider view of the outside and enlarge the interior space. The bay windows are used on sunny sides in colder climates, over sections facing road side, garden and other natural scape.

There are three basic types of bay windows. In full bay window the opening stretches from floor to ceiling level to create a nook in a room. In half or part bay window the window starts at seat or nominal sill level and reaches head height level or full ceiling level. In the third version the bay is more of a flower box projecting out. The nook created by full bay window is well illuminated and has better view of outside so it is used as study area, breakfast space, solarium, hobby area, etc. For these purposes the inner ledge of the bay window is used as built-in seat.

The building act of 1707 in London and other towns of England did not allow projections on a road side, to prevent spread of fire along the wall. This was changed in 1894 so that windows were not required to be flush with the exterior wall. During the Victorian and Edwardian period houses began to have bay windows.

Ground Floor Bay window

■ BOW WINDOWS: A bow window, is a curved or polygonal bay window. Unlike the bay window, there is no middle window unit, parallel to the room. Instead, several small width window units (fixed and shuttered) are joined to form a bow shape. Bow windows first appeared in the 18 C in England and in the Federal th period in the USA. Bow windows are also called compass window and radial bay windows.

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■ MASHRABIYA: Mashrabiya is a projected window on second or higher floor in mainly in urban setting, but rarely in rural areas. Mashrabiya was used in houses and palaces although sometimes in public buildings such as hospitals, inns, schools and government buildings. It is commonly placed on the street side, but occasionally on the internal courtyard ‘sahn’ side. Mashrabiya windows are presumed to have formed during 12th C in Baghdad. Iraq and Egypt are two countries where many examples survive. They are more common in Eastern (Mashriq) parts of the Arab world then the western (Maghrib) parts. Basra is often called the city with Mashrabiya. It was introduced in France from its colonial sources, and called moucharabieh.

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Mashrabiyas are enclosed with carved wood latticework, composed of the lathe turned wooden sections called bobbins, in complex patterns. Smaller lattice openings in the lower section obscure vision from outside and reduce the air draft, whereas larger openings in the upper parts allow better air draft and illumination. Lattice design differs from region to region. Mid part of the Mashrabiya is provided with sliding or a side-hung shutter for a clear opening. Mashrabiyas are also lined with stained glass to form an enclosed balcony, and an independent space attached to a room. Mashrabiya in farm houses and for out of the town buildings are more open, with reduced amounts of lattice work and without the lining of glass.

Egyptian Mashrabiya projects out at a slightly raised level providing for a Dakkah (a Dakkah is a masonry platform attached to the front part of a house, covered with a rug, it is used for informal talk and tea in Arab rural areas, an arrangement similar to Ota or Otla in a traditional Indian house) or in front of the window similar to the Indian Zarokha.

Mashrabiya adds space to rooms on the upper floor without increasing the foot print area of the building, but these have also been used for correcting the shape of upper floor front room. Mashrabiya allows air from three sides to enter, even if the draught outside was parallel to the house facade. Mashrabiya also provides shade for the ground floor windows.

The word Mashrabiya has varied origins. Mashrabiya denotes drinking or absorbing. The name perhaps has derived from a wood lattice enclosed shelf located near a window to cool the pots of drinking water. The shelf evolved until it became part of the room with a full enclosure. Mashrabiya also has originated from verb Ashrafa =to overlook, ignore or to observe.

■ SHANASHIL: Shanashil (shanshool or rushan) is a porch, verandah or gallery like features covered with fine wood lattice work. It is found in old Iraqi houses of Baghdad. Shanashil is also a net or wood screen-covered verandah or porch over looking a street or garden.

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EVOLUTION of METRIC MEASURES SYSTEM

by Gautam Shah  ➔  These few SLIDES present Evolution of Metric Measure System .

This Blog is in continuation of earlier one (Dated July 11 2014 – Slides up to 9) This one has Slide 10 to 18.

https://interiordesignassist.wordpress.com/2014/07/11/measures/

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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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