Tuesday, March 7, 2017

SHEER FABRICS


Post 146   by Gautam Shah

Sheer is tactile feeling that is satisfying and delightful. It is a feeling or a state of experience. Sheer fabric is a very fine, gossamer or diaphanous material that does not occlude vision through it. It is an important quality mark for lightness of mass. The word sheer is used to emphasize a state or situation that is extreme or complete, and does not involve any mix-up with anything else (does not involve anything else).

Tent Curtain Pixabay image by Unsplash

In the 1175-1225 period or Middle English word sheer (scīr, scere, shere, schere, shire) (cognate with German schier, old Norse skīr, Gothic skeirs) was used for a clear, free, bright, thin, shiny or water like material. Some of the synonyms are: utter, complete, absolute, total, pure, perfect, downright, out-and-out, thorough, thoroughgoing, through and through, consummate, patent, surpassing, veritable, unqualified, unmitigated, unalloyed, unadulterated, unmixed. 

 
Old Window with curtain Pixabay image by Paul Brennan Winder/USA

A Sheer fabric has three basic qualifications: It is thin or lightweight, It is translucent, and it is very supple. The lightweight features come from the quality of fibre material, its filament or spun thread (denier), the low density construction through knitting or weaving. Its translucency derives from sectional form of the fibre, degree of spinning, massing during spinning and weaving, and minimal or no addition of processing materials like dyeing, sizing, etc. Its suppleness results from the quality of fibre material, the low denier of fibre or filament, and avoidance of massing during spinning and weaving.
 
Sheer curtain with pattern > Pixabay Image by Unsplash

Sheer fabrics from natural fibres such as Silk, have yarns with multiple fibre stands, whereas Cotton has several staples entwined during spinning. The natural fibres create a fabric that is dull or with small sheen. Rayons are produced as staples, and so have slight sheen, unless treated differently. Synthetic fibres such as Nylon and Polyesters are filaments or very long staples, and usually with uniform cross sectional shape, and so provide glossy face.

Sheer curtains > Flickr image by Ket

Sheer fabrics are made from very thin threads and have low density construction, through mainly weaving, but sometimes through knitting. Sheer fabrics of netting type have comparatively low gloss due to greater de-fraction of light. Denser weaves have more sheen or shine. The density of a fabric (knitted or woven) is determined by several factors such as sectional form the fibre, degree of spinning, massing during spinning and weaving. The resultant fabrics have various levels of translucency. Sheer fabric of low density weave is supple, but a flimsy cloth.
Occluding the view with sheer fabric > Wikipedia image by TriviaKing (talk)DWS-Montag Zen

Denier is a unit of measurement for fineness of fibres or filaments, as threads, expressed as the weight in grams for 9,000 metres length of yarn. The surface area of a fabric is directly related to the denier. Smaller deniers yield more fibres per unit weight of the material. A micro-fibre is less than 1 denier, fibres for sheer fabrics are finer, just 0.9 denier, in comparison, a human hair is 20 denier.

Fabrics with a high denier measure are bulky, sturdy, durable, but nearly opaque, whereas fabrics with a low denier measure tend to be sheer, soft, and smooth. A fabric, of 3-5 denier is like a clear film, extremely thin. Ultra sheer refers to very light deniers of stockings or pantyhose, usually 10 or less.


Celula Nave "It happens in the body of time, where truth dance" Art installation in Nylon and Polyester Sheer fabric > Wikipedia image by Celula Nave Ernesto Neto (2004)/elefterial1
Sheer fabrics have a crisp to soft feel, depending on the quality of fibres and the density of weave. Fabrics’ coarseness or fineness, are mainly due the techniques of weaving. It is measured in warps or ends per length and in wefts or picks per length. Sheer fabrics include: Silks, Cotton, Rayon, Nylon, Polyesters and other synthetics. The fabric forms are crispy organdy, organza, voile, lawn, georgette. Supple forms include natural silk (unsized), artificial silks, rayons, tulle, netting, gauze, Gossamer, muslin. Soft sheers are difficult to stitch in comparison to crisp sheers. Art Silk or artificial silks are heat and chemically treated, or co-spun with rayon, cotton and silk staples to achieve desired level of feel.

Glow curtains Pixabay image by Pexels
Sheer fabrics are favoured for garments and draperies due to the suppleness (fall, contouring), transparency and low weight. Sheer fabrics are too thin to control incoming sunlight, but cause its de-fraction. As a curtain the sheer fabric allows sunlight to pass through during daylight, while maintaining a level of privacy.
 
Spanish Colonial era House 1780s > Wikipedia Image by Infrogmation of New Orleans

Early glass for windows was a flattened plane from cylinder or a flat cast sheet, but available in small sizes. Flattened glass had crinkles, whereas the cast sheet was unevenly polished. The vision through it was distorted, muddled or frosty. The sheer curtain masked the vision through the window. Sheer curtain fabrics do not offer any insulation against heat or cold, so need additional layer of heavy-opaque fabric curtains. Sheer curtains over bedsteads provide a romantic transparency. Sheer fabrics of low denier and high count weaves have little sound absorption, but higher proportion of gather or creases which add to sound absorption capacity.

Green Hued Sheer curtain > Flickr Image by Jessie Lynn McMains
 

Sheer fabrics for curtaining look best in their natural colours (original colour of the constituent fibre) or very lightly dyed or bleached shades, such as white, off-whites, cream, ivory, shades. Though many base-shades and prints are available. Lighter colours are preferred, due to the greater capacity to defract the light. Colour tinted sheer fabrics were popular to tinge the room with the particular hue. This is no longer needed, as vast varieties of paints and wall finishes with subtle variations of hues are available.


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Tuesday, November 22, 2016

DE-WINDOWING

Post 145   by Gautam Shah

Fenestra-Window and Defenestration-Dewindowing

The Latin word FENESTRA (plus the normalizing suffix -ation) stands for the WINDOW. Fenestration in modern sense is an act of opening multiple (computer) screens or windows simultaneously. The word Defenestration comes from the Latin de- (down or away from) and fenestra (window or opening). That is why computer hackers humorously refer to it as the act of removing Microsoft Windows from a computer.

 
Defenestration > Wikipedia ART by Karel Svoboda 1824-1870

Historically DEFENESTRATION has been an act of throwing someone or something out of a window. It connotes the forcible or peremptory removal of an adversary. It was often said, if you throw your adversary out of the door, chances are the person will come back with more vigour, but by de-windowing (defenestration), the action is injurious or fatal. Historically, the word defenestration referred to an act of political dissent. ‘In December 1840, Abraham Lincoln and four other Illinois legislators jumped out of a window in a political maneuver to prevent a quorum on a vote’. In the "Cologne Defenestration,” during the Revolution of 1848, an agitated crowd forced their way into the town hall of Cologne. Two city Councillors panicked and jumped out of the window.
 
(New) Town Hall Prague place for defenestration > Wikipedia image by VitVit
 
The term Defenestration originates from two incidents in history, both occurring in Prague. The First Defenestration of Prague involved killing of seven members of the city council by a crowd of radical Czech Hussites on July 30, 1419. Jan Želivský, a Hussite priest of the Church of Virgin Mary of the Snows, led his congregation on a procession through the streets of Prague. It was as a result of the growing discontent at the inequality between the peasants and the Roman Catholic Church, the Church's prelates, and the nobility. The enraged crowd stormed the New Town Hall (Novoměstská radnice) and threw the councilors out of the windows onto the spears of the armed congregation below.

Defenestration ART by Matthaus Merian the elder 1593-1650
 
The Second Defenestration of Prague was when the Roman Catholic officials ordered the cessation of construction of some Protestant chapels on land which the Catholic clergy claimed belonged to them. This was interpreted as a violation of the right of freedom of religious expression, and two imperial governors were found guilty. They were thrown out of 16-meter high windows of the Chancellery. The governors, however, landed on a large pile of manure and survived unharmed. 

Death of Jezebel > ART by Gustave Dore (1832-1883)
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Thursday, September 22, 2016

FUSION JOINING without using any intermediate material

Post 144   by Gautam Shah 

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Fusion joining without using an intermediate material, are used to join mainly metals and thermoplastics. Fusion joining is a common term used for many different types of welding processes. The welding processes rely on high temperatures that change the phase of materials to be joined aided by pressure (or impact). For phase change, the materials to be joined should have same softening-melting temperature and nearly similar composition.

Raincoat with fused joints > Flickr image by Mantelmann

Fusion joining as a category may include many other nearly similar processes, but which involve an intermediate to form the joint. There are three categories of such fusion joining systems, Soldering and Brazing, where the work pieces are not melted, yet joined using a meltable filler material, Welding the work pieces, and in some instances, the filler material, both are melted, and Chemical fusing or solvent welding (which are actually forms of adhesion fixing), where plastics are joined by solvents to dissolve (soften) the surface areas of the work pieces. The joint is created with or without application of pressure.


Brass vessel making 4 by Forging joining > Flickr image by McKay Savage  (HiH - Enterprises - MSE  )
The first fusion joining process was the forge welding. Blacksmiths used to beat the heated metals like brass, copper etc. for joining. For heating the work pieces, wood, charcoal and later mineral coals were used. Forging: Forging was an ancient process of hammering to shape materials like iron and other malleable metals, or by pressing (or rolling)in their plastic state (by application of heat).

Forged joints of Brass vessel at Madhurawada Visakhapatnam India > Wikipedia image by Asityamadhav83
 Forging has many modern versions. In these variants, the heat is created by electrical resistance, friction, laser beams, etc. Continuous pressure or intermittent impaction is done to fuse the heated components. Forge welding components are in sheet, or small section forms.

Forging created desired form, but also refined the grain size and arrangement, and thereby improve the structure of the metal. Forged metal is stronger and more ductile than cast metal, and exhibits greater resistance to fatigue and impact. Forging is also used to compact materials by removing gases and by packing the cavities.

Butt or spot welding is a widely employed technique for assembling sheet components of metals and plastics like car bodies, cabinets, furniture. It is a type of spot resistance welding. A high electric resistance-heat softens the material close to the melting level, and under pressure (of impact) the thin walls fuse and join. The joint developed has no apparent deformity, except a charred spot.
 
Wrought iron joints > Pixabay free images by avantrend


Seam or strip welding: Seam or strip welding is also a type of resistance welding method. It is used to join overlapping metal sheets of up to 3 mm thick. Instead of pointed (butt end) electrodes, and wheel-shaped electrodes roll along the work-piece, making a long continuous weld. Weld strength though is lower than other welding methods. The method is suitable for specific uses like formation of seamed pipes, and in terms integrity it is a fairly reliable process.
 
Blister packing -fusion joining > Wikipedia image by Alex Khimich
 
Seam or strip welding is also used for joining plastic sheet materials, like raincoats, wind-cheaters, shopping bags, containers, etc. In one process the sheet materials to be joined are pressed by a preheated straight wire, knife or a roller.

Induction welding is a form of resistance welding. Here the materials to be joined are heated by induction (non-touching or a distanced heat source). For this purpose a coil wrapped around a cylinder, causes opposite direction magnetic field in the materials, to melt-join together.

Butt fusion welding creates a joint between pipes gas and water pipe or other sections of doors, windows etc. The ends are pressed against a heated plate, and brought together to form a ‘beaded joint’.

Fusion joining requires a heat source, such as a gas flame, an electric arc, a laser, an electron beam, friction, or ultrasound. Fusion joining sometimes requires a slight to very heavy pressure. Forging is a very noisy process. Fusion joining is done under many different environmental conditions like open air, rain, frost, underwater in vacuum or space and sometimes under the shield of inert gases like Nitrogen, Argon, Helium, Carbon dioxide, etc. Fusion joining in spite of all care is essentially a hazardous procedure. It involves risks of high electric currents, high temperatures, sparks, fumes, and radiation.



Felt Cloth non woven assembly of fibres > Wikipedia image by en:User:Sannse from english WP

There are several other joining systems that use pressure, but not the heat (high enough for softening or melting). Here the (often purposely disarrayed fibres) two surfaces are pressed or rolled together to form a joint. These techniques are used for joining fibrous surfaces like papers, leathers, woven and non-woven fabrics, etc.
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Monday, August 29, 2016

UNDERSTANDING NON GLAZED versus GLAZED CERAMICS




Post 143   by Gautam Shah


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Making a pot with coil technique > Wikipedia image by Poupou l'quourouce
Clays are fine albuminous products formed by decomposition of igneous rocks. Clays are tenacious and plastic when wet. Clays are highly cohesive, have high capillaries and no internal friction. Clays are smooth to touch, sticky and plastic. Clays can also be classified according to their plasticity, or silt content. Hard clays or stiff clays have low sand content, and are difficult to excavate. Fine clays have medium sand content, and can be excavated with slight effort. Soft clays have coarse texture and are easy to excavate. Pure clays are mostly useless because of the high plasticity and excessive shrinkage on drying. Clays, if very plastic, are called fat clays, whereas less plastic clays are called lean clays.
 
Top layer or organic soils have substantial amounts of organic matters, from the decomposition of vegetation and human, animals excrete. The presence of organic matters makes a soil light in weight and dark in colour. Organic soils usually show high workability and low shrinkage characteristics. When organic soils are found below an existing layer and are old, contain gallic acid and tannin in small proportions, but sufficient to act as fungicide and mild insecticide.
Incised ceramics in Mexico > Flickr image by Giulian Frisoni

Virgin or non organic soils have negligible amounts of organic matters, and so reflect the basic characteristic of the predominant constituent element present, i.e., lime, silica, or alumina. However, soils do take-on the personality of the other minerals present in it. Non organic soils unless constituted by colloidal particles show very little plasticity. Some mineral constituents of such soils are reactive to water resulting in swelling and leaching. Kaolin or China-clay, is pure mineral clay that is used for making Porcelain. Ball clay is added to other mineral clays for plasticity. Fire clay is used for high heat resistance items, such as for kiln lining bricks.


Clay Deposits Estonia Wikipedia image

Clays are black, white, red, brown and yellow in colour. China Clay is a residual material, contaminated with silica, mica, feldspar and decomposed feldspar. Ball clay is a sedimentary material of fine grain size and some organic contents. It is finer than china clay. Fire clays are formed from feldspar as residual and sedimentary deposit. Brick clays are high in iron content, and impurities of calcium compounds and organic matter.


Unglazed pottery in India > Wikipedia image by McKay Savage from London UK

 
Clay products forming process is determined by the clay ingredients and the shape or form and size of the object. It is Semi dry or semi plastic process, Wet or plastic process and Liquid processes. Semi plastic processes are adopted where water supply is scarce, and the condition of soil is very plastic, where high density mass by pressing is possible. This is used for forming building blocks. In case of plastic soils, the addition of water causes swelling of the mass and an increase in cracking during drying, so some additives are required. It also needs high degree of compaction, mainly achieved on potters’ wheel and with thin body forms. The item has to be so designed that all parts even cross section thickness, and changeover from one thickness to another, if any, is very gradual. Plastic processes allow sufficient time to a craftsperson to mould and finish an article. Liquid processes are used where through mixing of ingredients is carried out in presence of water. 
 
Recuay Peru Effigy jar 100-300 BC > Wikipedia image by Helvetiker

Historically, unglazed pottery has been more common than glazed pottery. Unglazed pottery can be produced from wide variety of clays, and is comparatively easy to produce. Unglazed potteries are commonly identified as ‘earthenware and terracottas’. Unglazed potteries were first used for pots and vessels for storage and cooking, and materials’ processing. Later the uses included architectural elements like building blocks, drains and tiles for floors and roofs. Later ages saw development of three basic classes of ceramics. Very thin body or walled pottery produced on wheels, from comparatively good plastic soils, and controlled firing techniques. These were sometimes incised with decorations, or coloured with iron oxide pigments. The next class consisted of non-wheel based formations such as the coil method, used for creating larger storage utilities for grains and water. These were polished with clay slips and appended with clay decorative motifs. The third class consisted of figurines, toys, sculptures, of solid and hollow type, through press-cast and poured in the mould formations.

Brick Production Tanzania > Wikipedia image by Egbert in donker Afrika

Clay-based potteries are also called Terracottas due to the reddish colour, imparted by Iron oxide as ferric and ferrous. Other important colourants are quartz, kaolin, mica etc. Soils show a wide range of colours from off-white to yellow, light brown and chocolate to radish tones.


Terracotta work on Shyamrai Temple Bishnupur India > Wikipedia image by Amartyabag


Clay products are baked at different temperatures depending on the constituent clays, form, shape, size, mass, and the use of the product. Earthenwares are comparatively low temperature (approx. 1000°-1200° C), Stonewares are mid temperature range (1100°-1,300°C), whereas Porcelains are fired in the range of about 1200°-1400°C. An oxidizing atmosphere inside the kiln, allows air and affects the surface and appearance of the products. Whereas by limiting the oxygen in the kiln, some glazes change the colour.

 
Roman Amphora 520-510 BC Wikipedia image
 
A ceramic can be decorated before or after firing. Glazing is one such process to make a ceramic product more opaque or less permeable. Glazing process may add colour and lustre. Sewer pipes etc. produced from low-cost materials are salt-glazed during the firing to provide impermeability. Other products are glazed in raw (green) form or after first stage of firing. Building blocks are left unglazed, as porosity increases cement bonding.

 
Terracotta Etruscan Sarcophagus of the spouses > Wikipedia image by nl:Gebruiker:GerardM
 
Glaze is a combination of materials, consisting of glass-forming minerals (silica or boron) combined with ‘stiffeners or bodying materials’ (such as clay and fluxes) and melting agents (such as lead or soda). In raw form, glaze can be applied to the unfired pot, or after an initial, or biscuit (or unglazed) firing. Many kinds of glazes are used. Some heighten the colour of the body, and others mask it. Basically, there are four principal kinds of glazes: feldspathic, lead, tin, and salt. Feldspathic, lead, and salt glazes are transparent, tin glaze is an opaque white. Hard porcelain takes a feldspathic glaze, Soft porcelain usually takes lead glaze. There are many other modern glazes that do not fall into any of these categories.

 
Glazed Celadons Pottery Longquan Zhejiang China 13 C > Wikipedia image by Vassil
 
Slip (liquefied clay strained of coarse particles) may be used for imparting specific surface finish. Slips are applied to completely dry, or half-dry items by coating or dipping them into the slip of creamy consistency (to which colourant is sometimes added). Slips can be brushed, sprayed, or trailed on with a spouted can or a syringe. Designs can be drawn or incised with a pointed tool into the slip to reveal the body, a technique known as sgraffito.

 
Dish with Cyprus decorations Iznik, Turkey 1570 > Wikipedia image by deror avi 2011-02-19 07:58:48
 
Alkaline glazes, popular in the Middle East, are shiny and frequently transparent. They are composed mostly of silica (such as sand) and a form of soda (such as nitre). Lead glazes are transparent, with traditional types made of sand fused with sulphide or lead oxide. They were used on earthenware by Roman, Chinese, and medieval European potters and are still employed on European earthenware. Tin glazes are opaque and white. Metal oxides give colour to glazes. Copper makes a lead glaze green and an alkaline glaze turquoise. Iron produces yellow, brown, grey-green, blue, and with certain minerals, red. Feldspars (natural rocks of alumino-silicates) are used in stoneware and porcelain glazes because they fuse only at high temperatures. Glazes or their firings, if defective show pinholes, bubbles, crazing and peeling. Metal coating, enamelling, minakari, etc. are ceramic like coatings or depositions of metallic and non metallic compounds. Vitreous enamel coatings are glassy but non crystalline coatings are matt.

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Tuesday, May 31, 2016

CORRIDORS


Post 142   by Gautam Shah

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Corridors are formal transfer zones in buildings, but sometimes passages get formed with intense movement conditions between two points. Corridors are architecturally articulated built forms, whereas passages are marked or delimited sections. Corridors and passages are distinguished by barricades, flooring differences, sensorial markings, graphics and signages.

Meenakshi temple Corridor Madurai India Flickr image by Jean-Pierre Dalbyra
 A corridor as a built form is highly a formal entity and it is difficult to breach the discipline, but passages have no formal structure, and can be overstepped. A corridor is a passage, but a passage needs to be well modulated to become a corridor. A corridor without the traffic, will still remains a corridor, but a passage without movement just merges in the surrounding space. Corridors are more formal then passages, but passages allow greater public participation, and so ceremonial.
 
Corbet's Couloir -a ski run or passage Wikipedia image by Enricokamasa

Alleys, arteries, aisles, channels, lanes, couloirs (narrow passageway on a hill), tunnels, paths, lobbies, vestibules, avenues, all have one common element: a linear passageway. A labyrinth and maze, are entwined passageways, where the former one ‘has a single path -unicursal, reaching the centre; and the later is a complex branching -multicursal puzzle, with choices of a path and directions’.


Labyrinth Chartres Cathedral Wikipedia image by Maksim
Corridors and Passages, as transfer systems in buildings are well defined and functionally supported by other systems. Such transfer systems become ineffective, if design definitions are improper, have inaccurate capacities, or lose the validity due to the changed circumstances. When a transfer system becomes ineffectual, many other systems in the building become useless.

Books in Corridor Pixabay image by Unsplash

Corridors, are defined or recognized as passageways, connecting a point to point location, or several ones on the way. Corridors are defined by architectural features, distinctive materials and environment, sensorial recognition of their existence, signage, and preference for the shortest and easiest access route.

Corridors originate at points of transfer such as doors, other branch corridors, stairs, elevators etc. Corridors also occur where conditions for superior and efficient transfers are available, such as: shaded or protected areas, finer floorings, smoother gradient, pleasant surroundings, promise of fulfillment, expectancy, escape from hazards.

Passage Junctions Pixabay image by ujeans

Straight corridors provide a very efficient mode of transfer, but tend to be monotonous. Straight corridors allow continuous acceleration, which may pose problems to other transferees. Corridors with zigzag or variable movement directions heighten the expectancy. Circular or curved corridors tend to align the movement concentrically. Bidirectional movement corridors increase the social interactions among the users. Multi directional and multi velocity movements destroy the character of a corridor.
 
Main hall Brussels railway station > Wikipedia image by Saber68

Corridors are heavy movement areas, compared to many other spaces used for casual transit. Corridors, due to heavy traffic create environmental interference of noise, vibration, dust and spread pollutants and infections. Corridors enhance the fire hazards and security risks; however, if properly designed, may curtail such risks. A straight corridor can be policed from one point, but so an intruder (terrorist) also can command the entire corridor.

In complex buildings variety of work spaces, each with specific environment and controls are required; corridors as buffer zones isolate such spaces. Corridors create an intermediate or equitable zone of transfer for all such connected units. Corridors provide a strong cohesive identity among apparently very unrelated cells.

Main committee corridor Westminster London > Wikipedia+Flickr image by Mark Kobayashi-Hillary

 Corridors are ideal, if without any encumbrances, like cross passages, doors, and architectural transgressions (projecting out or receding in). But very long corridors, such as at Airports and underground metro services, without intervening interests become boring. Corridors are common utilities, so have several services attached to them, such as, toilets, drinking water fountains, fire fighting systems, emergency exits, air handling units for air-conditioning systems, seats, electrical mains, bulletin boards, exhibitions, first aids, security checkup systems, food and beverage dispensing systems and signs. A Tirupati temple (India) corridors are also used by devotees as a place to sleep, rest, eat, bathe and pray during the long wait for the Darshan.
 
Parikrama around Girnar Mountain Gujarat India > Wikipedia image by Nileshbandhiya
 
The word Corridor derives from Italian Corridore =place or space to run, which in turn has derived from correre or Latin currere='to run'. By association courier, meant a man or horse who could run to deliver messages, money or documents. Italian word corridoio is a place, or rather space for the courier (man or horse) to run.


Ponte Vecchio and Vasari Corridor from Galleria degli Uffizi > Wikipedia image by JasonF007

From later part of 16th C. Corridors were strategic spaces or routes of access in fortifications. Couriers and corridors were used for quicker deliveries by the military. It had military ramifications for defence or offense, but very little civilian relate. The space for a faster messaging, the corridoio was not a marked territory or a facilitated ground within a fortification or dense urban setting. It was simply a familiar-well travelled precinct. In late 16th C it denoted a military term for a narrow strip of land along the edge of a ditch or fort-wall sometimes protected by a parapet. It was also a narrow passageway along the slope of a hill and sea. Trails are marked passageways but in the wilderness. Trails are so narrow that most vulnerable or unafraid ones lead the way, and others must trail.
 
Secret passage between Vatican and Castel SaintAngelo Rome Italy Wikipedia image by Patnaik+ Alessio Damato
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Thursday, May 26, 2016

WORKING of INTERIOR DESIGN PROFESSION

Post 141   by Gautam Shah


Interior Design as a profession is changing at a very fast pace. Today many different forms of interior design practices exist, ranging from

Pure design (only),

Design + Supply,

Design + Supply + Execute (install-fabricate-operate).

Frank Lloyd Wright Pope-Leighey House > Wikipedia image by Cliff from Arlington Virginia USA

These classifications arise due to ethical reasons (professional bodies, governmental regulations, etc.), taxation, traditions and business convenience. There was a time when Interior designer or decorator worked on a site or few sites, within the travelable region. In very large, complex and remotely located projects, however, it was not feasible, for the designer or their representative to be present all the time on a site, and conduct the projects. Interior Designers, as a result, gradually began to limit their work to design matters only, and let other agencies handle the supply and execution. The practice of employing or appointing ‘third party venders or contractors’ serves varying degree of efficiency, reliability and satisfaction, for corporate or government types of organized clients.
 
Print 1833 of Dome of Rock Jerusalem > Wikipedia image by Georg Dehio/ Gustav von Bezold

In recent years large number of holistic Interior Items and systems have become available. These vendors (such as of modular kitchens, Toilets, Ceiling, Acoustics+Ceiling, Painting and other surfacing, Glazing, etc.) offer complete installation services. So Amateurs and Lay-users prefer services of such supply-install venders.

Vendor-Supply Interior Design Practice through use of Catalogues (by James Shoolbred & Co. 1876) Wikipedia image
 On the other hand, small practice designers found it more convenient to mange execution along with design. Designer self executing their own design often worked, without premeditated scheme. Designers, who lacked the capacity to detail out or document a project, preferred this route. These small time designers or amateurs have a capacity of creating design images (representations like Isometric, perspectives, 3D images, etc.) which are used as presentations for enticing a client. These amateurs rely on known craftspeople who can execute the design from such images and workout the lacking details.
 
Diagram of three corbel brackets at Chinese Hall by Official and architect Li Jie 1103 Wikipedia image by PericlesofAthens

There was a time when a Designer had to specify raw materials and the process of assembly or manufacturing to generate a product or a functional system. To check the suitability of the delivered product, and operative validity of the system, a series of tests and check parameters are also required. Very often these parameters remain worthless, because neither, the required level of manpower and testing equipments are available at a site, nor is it feasible to take the product or system from site to such locations.
 
Jasper Morrison Furniture in the Musee des Arts Decoratifs > Wikipedia image by Gael Chardon from Paris France
 Design needs are now documented in terms of ‘performance specifications’ or optimum operative functionality to be attained by the vendor or contractor, with their choice technological input (materials or manufacturing). This type of modern design documentation requires high level of skill input, technological knowledge-ability and professionalism. Amateur or untrained (hobbyists) interior designers do not have such proficiencies.
 
Documented design by Robert de Cotte 1700s

The separation of design and execution, is also favourable arrangement from point of view of Taxation. Pure Design practice is liable for simple taxation like Service Tax. In Design + Supply practice, a designer may be liable to pay other taxes (Sales Tax, etc.). Design + Build practice, is though an accepted norm in many countries of the world.

 
McElroy Octagon House on Gough st San Fransisco Cal 1891 Credit Library of Congress Prints & Photographs Division WIS,28-WATO,1-

 Interior Design like any other Design profession, is a dependent profession. Interior designers work in conjunction with other design professionals, needing interior design inputs in their projects, such as Architects, Building engineers, Landscape designers, Furniture and Product designers, Exhibition and Event managers. Interior designers also use expertise of other professionals for their work. These include environmental engineers, ecologists, furnishing experts, textile designers, painters, sculptors, and an array of crafts persons.

Pixabay Free image by stokpic
 Some degree of specialization is becoming apparent in Interior Design. Some of the major fields to have distinct identities within the ambit of Interior Design are: Hospitality or hotel design, Entertainment facilities, Public space design (air ports, railway stations), Exterior design or Street architecture, Exhibitions and events planning, Retail designing, Transport interior design. These fields naturally demand a varied manner of design approach and handling.
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