SURFACE MODIFICATIONS

Post 647 -by Gautam Shah

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Natural and Industrially-produced materials require some form of surface modifications or treatments, before being put to functional use, or for readying them for the next process. Surface modification at a basic stage, consist of cleaning and mechanical scrubbing. The surface modifications are for creating use-worthiness by levelling, texturizing, or for application of additional materials for shielding. The surface modification starts with visual observation and touch-feel experience that no foreign materials have remained on the surface, and all loose (removable) materials are removed. These simple processes ensure integrity of the surface.

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The next level of surface modifications are applications like coating, physical-chemical treatments, cladding, mounting, plating, joining, welding, levelling, cleaning, washing, ph balancing, static removal, etc. Surface modifications are intently surface preparation processes and may impart radically different surface qualities such as textures, ionization, etc.

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At another level Surfaces Modifications are not attempted, but such situations are negotiated with technologies. These include defining means to override the hindrances of texture, handling issues, electrical and other properties. These technologies also include forming shields around the users, tools and other equipments rather then over objects. The shields are physical layers and non-physical arrangements like restricting the exposure through time-space management.

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In early ages, the surface modification and applications were an integrated process for exploiting the surface of any object. Primitive arts and crafts had a comprehensive treatment that consisted of 1: Modification of the surface, 2: Application of surface forming materials, and 3: Rendering new textures and tonal variations or shades. At a later stage an additional treatments for protection of the new surface were devised.

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Surface modifications are physical, chemical and mechanical processes.

The Physical processes are mainly used to remove unwanted particles or materials (such as rust, nodules, residual deposits, dust or grease, lubricants, cutting-oils, etc.) adhering to the surface. Rubbing, air-dusting, vacuum cleaning, wiping, water-bathing, etc. remove such adhered materials. The particles have remained on the surface due to the holding by surface texture, bonding or ion attraction, and horizontal storage. Washing with soap or a surface active agent (surfactant) can weaken the ion attraction break the weak molecular bond generate by-products that can be removed easily.

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The Chemical processes include acid-alkali treatments and solvent washing. The processes roughen, etch or smoothen the surface. In many instances the resultant by-product is beneficial or neutral, and so allowed to remain on the surface. In other instances a secondary treatment is required just to remove the by-products of the first treatment. Sometimes Surface preparation agents themselves are the primary surface finishes. Such agents cover the surface area as an intermediary film. Such films help in bonding of the final surface finish. Chemical processes also include burnishing, flame-treatments, surface annealing and hardening, cathodic modification, sputtering and material’s depositions.640px-A_brass_utensil

The Mechanical Processes affect the surface superficially. Cleaning of the surface by removal processes include abrading, grinding, rubbing, blasting, planning, chipping, etc. Other mechanical processes alter the surface with newer textures by engraving, patterning, planning, surface deformation, etc.

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Surface modifications processes have been used for body painting, pottery, home building, agriculture, mural or wall artwork, adornments, jewellery, ornamentation, household utilities, tools, musical instruments, etc. Surface modifications were explored pattern making, texture creation, personalization, cultural expression, totem, abstract or symbolic representation etc.

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Surface levelling is achieved by scrubbing or rubbing off the impurities, removing select protruding sections, or by skinning the entire surface area. In later cases there are chances of removing a seasoned or matured face and exposing a fresh one. Partial scrapping of the surface creates qualitatively unequal zones. This is the reason why over the ages levelling ‘plasters’ have been preferred. The ‘plasters’ can be thin coating, or an application of thicker mass. These were often rendered with patterns and textures or ‘loaded’ with minerals and colourants. Wet surfaces were, either, engraved or embossed with patterns to encourage the penetration of colours, to produce a bas or relief effect, or provide a highlighting boundary to the drawn object. Colours were blown as dry powders or applied as pastes and dabbed (pressed) into the wet plaster.

Gesso, a mixture of plaster of Paris (or gypsum) with size, is the traditional ground. The first layer is of gesso -grosso, a mixture of coarse, un-slaked plaster and size. This provides a rough, absorbent surface for ten or more thin coats of gesso sotile, a smooth mixture of size and fine plaster previously slaked in water to retard drying. This labourious preparation, however, results in an opaque, brilliant white, light-reflecting surface, similar in texture to hard, flat icing sugar.

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RATIONALIZING DEMANDS for OBJECTS and their SURFACE SYSTEMS

Post 640 –by Gautam Shah

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Objects and Surfaces have their demands, which must be tackled before one can use them. Objects are used for their dimensional features, mass, form, engineering attributes, and other consecrations like cost, availability, ecology, etc. whereas the surfaces are used for sensorial purposes. Objects and Surfaces are rationalized to prepare them for technical use, handling, environment and assembly.

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Stone Wall > Pixabay Image by GregMontani Bayern

We do so by matching the requirements with readily available lots. However, we need to prepare, process or manufacture the objects or surfaces through several conversions. The processes of rationalizing, though begin with the object-modification, may eventually include changing the environment. Changing the environment immediately can bear upon a very vast field of actions. Like the old fable, for the king it is more efficient to cover own feet with leather shoes than layer streets of town, to protect from dirt’. ‘Similarly one may open the umbrella during the rain and not at other times’. It is more efficient to deal with the environment in space and time.

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The Parthenon -West side Weathering and usage > Wikipedia image by Yair Haklai

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Positional or differential weathering > Keshav Temple in Somanthpuram India  > Wikipedia image by Hemanth M Y

The time and effort expended in modifying the entity or its environment, is not very efficient. It is often more effective to compose a new entity (functionally, technologically and economically), than expend too much effort in improvising it. It is better to buy a new razor blade with a sharp edge, than polish the blunt one, or join a bone mechanically, than allow passage of time to do so.

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Tennis Balls – Multi material objects > Pexels image by freeimages9.com

Objects and the surface systems, if of single material, the operative demands are simpler, but if composed of many materials (similar or dissimilar), have complex and often in-specifiable demands. It is ideal to reform the object entity by integrating its surface systems with it. Where such one-to-one integration is not possible, the object entity and its surface system both may be individually refashioned to become each a single material entity.

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Diverse and Multi layered treatment of windows > Pexels image by Unsplash.com

A surface system can be facilitated by delaying or curtailing the effects of environment, for the functional period of the entity. Environmental effects are from specific orientation and for duration, and so a surface systems can be designed to be selectively local or dynamic. Liquids and gases have no stable object boundary, so must be contained, and for such material phases the container becomes the apparent surface system.

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Nuclear waste Storage > Wikipedia image by Bill Ebbesen

Ordinarily surface finishes are fashioned, only after the object and its relevant environment have been conceived. But sometimes an object could be so hazardous that until a really workable surface system is designed, the object cannot be allowed to exist or function. Similarly an environment could be so harmful that till an appropriate finish system is devised the object cannot exist, much less function in it.

The environment influences objects in such a complex way, that any search for logic is sometimes impossible. This is the reason why many surface makers seem to work with their intuitive faculties. To some people, ‘providing a surface system is an art or craft, rather than a scientific discipline’.

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Car assembly and finishing is a single process > Pexels image by Mike

At any cross section of time, we find a large number of surface systems are overtly attached to the object or in the process of being integrated to the entity-base. It is very necessary that a surface system in such a situation, be singular in constitution or at least be effective in that manner. Finish makers aspire to provide a singular surface system in place of a multi-component system. However, in a finish maker’s world there are very few situations where singular surface system can satisfy all the demands. Multi-component surface systems are reality.

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Installation of base for MUGA tennis court > Flickr image > credits > http://www.softsurfaces.co.uk

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STUCCO WORK

Post 299 – by Gautam Shah

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Stucco work has been interpreted as architectural plaster work, surface texture rendering, painting technique, ornamentation body and sculpting material. It has been also used as a wet ground for fresco painting and dry gesso surface base for painting. Stucco creates a dull or matt surface, so in recent periods it has been used for Calcimine or Dry Distemper and Oil bound Distemper (OBD)  painting systems.

Style European Art Stucco Rococo Facade Painting

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The varied interpretations across ages and cultures relate to the different techniques, materials and purposes, but all relate to surface rendering system. It is now often used for substantial coating systems that are applied with textural effect, convert into a textured formation, or allow ‘work’ post application. These coating systems are based on polymeric emulsions (or Latex systems, as known in USA).

complex of Sultan Qalawun Cairo

Stucco work has been persistently used for interiors, but more diversely on exterior surfaces. In interiors stucco was a surface forming system over which variety of coatings (such as Fresco, Encaustic, Oil, Acrylic) and mural making (such as glass, ceramics, inlay) techniques were applied. On exterior face it was used as a surface rendering (texture) system like for sculpting decorative motifs, figurines and statuettes, and for formation of applique architectonic elements (such as pilasters, tympanums, pendants, pediments, cornices, column fluting, pillars’ heads and bases).

Iran Stucco

Stucco-work began as a wall coating system, probably to rejuvenate the soot-covered walls (blackened due to oil lamp lighting and indoor fires’). It provided a smooth surface over a variety of wall surfaces such as adobe, reeds, brick and stone. Examples of stucco-work occur in the Aztec architecture of Mexico, Egypt, Sumerian buildings and Greek buildings. Romans erected masonry structures, often with recovered materials from ruins of earlier age buildings. These walls were of random pattern, and required plaster as well as textural renderings. For faster finishing of vast buildings, stucco was ideal system for interior and exterior work. With little craftsmanship it provided ‘sculpted and decorative’ artefacts for middle class to replace marble and other stones.

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Stucco work reached new heights during Baroque period. Renaissance period provided smoother stucco surfaces in buildings to contrast the rusticated stone’s corners of openings. Post Renaissance period saw festoons and medallions of stucco on exterior walls. During Gothic period stucco work applied to wood a lath lattice was used for creating intricate ceiling patterns. Walls had cornices, freezes and panels over wood base. It was also realized that a plain wood wall was darker in colour and was susceptible to fire on the other hand stucco or gypsum-covered walls could be painted by water-based coatings (lime-wash, calcimine, distemper, etc.) and, these were fire resistant.

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The basic ingredient for stucco work has been Lime, with addition of Gypsum and marble dust. Other reinforcing additives were hair, fibres, stone chips, etc. Gypsum was costly material, yet it was used with marble dust for imitation marble finishes called Scagliola. Since industrial revolution Portland Cement is being added, and in last 50 years polymeric binders are included.

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SINGEING

SINGEING

Post 264 ⇒   by Gautam Shah  →

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Singeing is a technique of controlled burning, charring or scorching the surface of a material. There are three important aspects of the process 1 the heat is intense, 2 the application of heat is of short duration, and 3 the affectation is not deep, but only surface based. Since prehistoric times the process has been used for many purposes. It was first created to burn of the skin hair of humans, and also bristles off the carcass of a pig or fowl in preparation for cooking.

Singeing was perhaps better method for trimming scalp or body hair for personal grooming then using a flint edge, however, sharp it may have been. For ritual activities charring skin with a burning wood stick or red-hot metal was very common. The burning wood rubbed into the skin, scorched it and allowed deposition of ash and carbon to colour it, as a form of tattooing.

Tattooing by burning

According to Herodotus (500 BC), aristocrats, tattooed themselves to show their social status. A Germanic barbarian tribe the Goth used tattoos to brand their slaves. In later periods Romans tattooed slaves and criminals. In China hot stamping of wrongdoers was a painful punishment and lifetime branding. In some tribes scarring the abdomen of women is used to denote her ability to tolerate pain, maturity and willingness to be a mother. Red hot cutting tools have been used to circumcise the penis, as a sterile procedure.

The word brand derives from Old Norse brandr = to burn. The word brand originally meant anything hot or burning, such as a firebrand. It may have its origin in the Dutch/Flemish word for a house or forest fire (brand), which is brand. The practice of placing a burn-mark over processed leather by tanners, over meat and cheese by farmers, was hot stamping. The same was perhaps followed by textile producers and processors. During Henry VIII period, a person who was found guilty for felony or murder was marked with the letter A on the thumb. The term brand-new is fresh from the fire, referring to items freshly tempered or stamped by fire, such as food.

The heat stamping of livestock to identify ownership is of very ancient origins. Symbols used for brands were part of the magic spell. The branding iron was an iron rod with a mark. Nowadays less traumatic super-chilled (cooled by Nitrogen) iron are used for branding.

Cattle Branding

Singeing is used by parlours to burn and shrivel hair over eyebrows and ears of males members and over the lip and neck-backsides of ladies. For these process, earlier candles were used to burn the hair and douse it immediately with a wet towel. It is now done with cauteries and laser instruments. Singeing is supposed to seal cut ends, close the follicles, and retarding the fresh growth.

Singeing Ear Hair

Cauterisation is used in surgical procedures to seal of the end of minor blood vessels during surgeries. It is also used by troops to seal off the bleeding wounds in field emergencies. It was once done by red hot stamping and now by electric sparking instrument. Lasers are used in a very similar procedure to remove cataracts from eyes.

Cauterie in Surgery

Home toasters, grills and barbecue equipments are provided with non sticking (usually alloys of Copper or Aluminium with Teflon coating) to imprint food with patterns. The charred patterns are singed marks. Direct torch flame treatment to bakery products like puddings, creates surface browning.

Flame torching Pudding

Flame cooking -singeing

Tarsia or Tarsiatura is technique of colouring wood surfaces by singeing and staining. It was used to create mosaic patterns in woodwork, in 15th C and later, in Italy. Controlled singeing created minor colour variations over walnut wood surfaces, due to burning and carbon deposition. Scrolls and arabesques, and sometimes architectural scenes, landscapes, fruits, flowers, were created by arranging or inlaying (marquetry) pieces of wood of different colours and shades. Tarsia technique was used for decorating the choirs of churches, backs of seats, in wainscotting (panelling) and for door panels.

Tarsia or Tarsiatura

Singeing also called gassing, is applied to both yarns and fabrics to produce an even surface. In case of yarns it may seal or trim the loose or protruding fiber ends, or deform or crimp it, giving a new textural feel and behaviour. In case of fabric it may fuse the synthetic component, loosen the stresses of weaving, smoothen the surface and increase the lustre. Singed fabrics soil less easily than non-singed fabrics. Singed fabrics allow printing of fine intricate details. When cotton fabrics are singed, it increases the wettability and gets better dyeing.

Heat setting is used in the textile industry to give fibres, yarns or fabrics dimensional stability, and attributes like higher volume, wrinkle resistance or temperature resistance. It is also used for posting creases in garment making.

Singeing or Spot heating by blow torch or very narrow flame helps in formation of enamelling of jewellery. Ceramic slip colours or oxide compounds are thin layered in micro receptacles and spot burnt to form an enamel or ceramic. This technique is also called Cloisonné.

Cloisonné

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GP – General Purpose Paints

Post 165  –by Gautam Shah

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In Building Industry many different types of finishes are used for covering non-masonry surfaces such as Ferrous Metals, alloys, aluminium, wood, and wood composites. In many cases the surfaces are composed of many different types of materials, textures and forms. Often the extent of each individual type of surface is so small and its composition so complex that it may not be feasible to attend to different surfaces.

HK_Sai_Ying_Pun_Des_Voeux_Road_West_Dulux_Painting_Material_Shop_3Most paint manufacturers offer a General purpose coating systems (GP) for such situations. The coatings are nominally conceived to be multi layer systems (at least of primer, inner and top-final coat). GP coating systems work for the inner and top coat, however, a primer coat is specific for the surface. It is specifically designed for the substrates such as masonry-cement primer, wood primer, mild-steel or iron primer.

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GP or General Purpose coatings are used for following situations:

On items that are difficult to coat– Such as deep grooves, undersides, inaccessible areas, narrow stripes, engravings, sharp corners and edges, very smooth surfaces, small parts like lattices.

On locations with difficult access– High level ceilings, external sides of windows in multi storey buildings, roof trusses.

In variable atmospheric conditions– Rain and snow storms, very high to very low humidity environments, dust, sun rays, wind, flying insects, very high to very low temperatures.

In single or multi coat systems– Some initial coatings at plant level as specific coating system and rest on the site as GP system.

For specific purpose– As a fresh system (on a virgin surface), as a re-application system (re-coating with a similar but over an aged surface) or as a renovation system (removal of aged coating layer, repairs and coating).

With peripheral hazards– Fire, chemical vapour and odours, colour dropping or running, and over-sprays.

GP enamel Painted Interior of Bang Pa In Chinese style palace

Such site applicable finishes are designed to dry out at normal atmospheric conditions. Most of the GP finishes allow multiple methods of application, and are applicable in widely variable atmospheric conditions.

Brooklyn Bridge painters at work high above New York City

GP = General Purpose Paints, as a term are nominally synonymous with Enamel Paints (Oil resin based), but now the term is also used for ‘Plastic’ emulsion paints (Latex paints in American terminology). Such plastic paints are masonry paints for walls,  roof-tiles, floors and stage-sets. These are often favoured over oil based enamel paints due to non-glossy (matt) finish and faster drying capacity.

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TEXTURES and MATERIALS

Post 162by Gautam Shah

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Removal of material Wood turning

A surface, is often the reason, why an object is being preferred or rejected for a use, and continues to survive in a particular setting. A user perceives the surface of a material-object in many different conditions. A surface is the most proximate and tangible part of an object. The proximity to a surface defines its visual experience whereas the tangibility refers to the mainly tactile sensorial characteristics. Texture is an important qualitative parameter of a surface definition. Textures are intimately linked to specific objects, and deviation from that is immediately registered.

Texture by Modification

Textures are part of naturally occurring objects. We also fashion new finishes by varying the textural qualities. An object acquires a specific colour ‘tinge’ as the texture affects the angle of reflection of light. The angle of perception also has similar effect. The quality of light (the spectral range) and its brightness affect the perception of texture.

  • There are more than 20 mathematical parameters applied to surface description, and some of the terms are: roughness, irregular features of wave, height, width, lay, and direction on the surface; camber, deviation from straightness; out of flat, measure of macroscopic deviations from flatness of a surface.

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Surface texture is a roughness that can be quantified by the vertical deviations from its “ideal form”. Surface roughness is a very subjective term what is rough for some context may be perceived to be smoother for other conditions. Surface textures are perceived for their extent. Surface texture is also sensed in terms of its proximity as well as its tangibility. A brick wall may be very rough to touch but a very extensive surface may not be perceived to be so rough.

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Textured surfaces have larger area, so greater reactivity with the environment. Roughness of the surfaces and have higher friction coefficient so susceptible higher wear. Surface irregularities are nucleation nodes for trapping of moisture and promote corrosion. Surface texture allows better adhesion.

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Textures are created by several methods, such as:

  • Removal of material >> Etching, Scraping, Roughening, Filing, Grinding, Engraving, Notching, Sculpting, Machining, Blasting, Shearing, Shaving, Singeing, Spluttering, etc.

Burnishing

  • Addition of material >> Painting, Printing, Dyeing, Metalizing, Material deposition, Plastering, Coating, Nitriding, Carburising, Galvanizing, Gilding, etc.

Diamond Polishing

  • By displacement processes like contraction and expansion >> Brushing, Rubbing, Ironing, Chasing, Repousse, Forming, Hammering, Forging, Beating, Levelling, Rolling, Buffing, Washing, Bleaching, Enamelling, Surface Alloying, Denting, Forming, Re-rolling, Peening, Spinning, Twisting, Weaving, Knitting, etc.

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