SURFACE MODIFICATIONS

Post 647 -by Gautam Shah

.

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.

634px-Fachwerk-Konstruktion-2004

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.

640px-Strasjo_kapell_wood_surface

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.

170117-F-NN403-001

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.

14935709370_be42a9c4b9_z

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.

business-woman-1824150_640

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.

529px-John_Cranch_-_Plasterer_-_Google_Art_Project

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.

640px-Shoe_Finishing_Machine

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.

Other related Blogs

.

 

 

Advertisements

RATIONALIZING DEMANDS for OBJECTS and their SURFACE SYSTEMS

Post 640 –by Gautam Shah

.

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.

wall-1395951_640

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.

640px-parthenon-acropolis_of_athens-2

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

640px-floral_scroll_and_deities_in_relief_at_keshava_temple_in_somanathapura

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.

pexels-photo-226586

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.

600-pexels-photo-127611

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.

640px-nuclear_waste_container_2010_nevada

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’.

pexels-photo-188710

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.

7194747118_c83788bccb_z

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

.

COATING of METALS -Part-I

Post 627 –by Gautam Shah

.

Handi-and-karahi

Shower Casting Vessel Watering Can Sprinkler

A coating is a thin surfacing that is applied or attached to the surface with various degrees of ‘chemical’ integration or amalgamation. Metal coatings are of four types: ‘Organic’ coatings like paints, organosols or other polymeric compounds, Non-Organic coatings of metals, Coatings of metalloids reaching to ceramic states, and Gas reaction-deposition systems.

640px-horses_of_basilica_san_marco_bright

Horses of Basilica San Marco > Wikipedia image by Author Tteske

Metals need a coating to alter the physical and chemical properties of a surface, such as to endow desired quality of texture, colour, patterns, electrical properties, surface reactivity, strength properties, etc. Often a surface treatment is in preparation for another treatment, as a temporary or permanent application. Maintenance of specific surface properties during sub-processing, transit, fabrication, installation and repairs require special coating systems.

506px-spouted_bronze_flagon

Copper Bronze spouted flagon 320 BC > Wikipedia image by Rosemania

Metal items require some form of ‘surface-deep’ preparatory ‘work’ to receive the coating, but such ‘work’ for small-or-thin-body entities like plates, sheets, foils, wires, threads may involve entire mass of the body. Post such preparatory work, involving heat leaves some stresses in the item. Small or thin body items have uniform stresses. But heavy items and assembled work can have differential stresses, which affects the final coating.

23280360783_d7e1f524af_z

Reclining Figure : Arched Legs 1969-1970 by Henry Moore > Flickr image by Pedro Ribeiro Simoes

One of the first Metal coating realized by Man was Patina. Metal rusting is nominally a crust like degradation products, but some metals like Bronze, acquire a surface layer over a period of time. Verdigris is the natural patina. Metal artifacts exposed to different environments such air, sea-water, soils acquire patina, a layer consisting of oxides, carbonates, sulfides, or sulfates. Patinas are products of surface mass degradation, and so etch or reduce thickness of the surfaces. Some patinas, however, curtail further degradation of the surface, and so are encouraged. Patinas are often visually appealing and so desired. Effects similar to patina can be achieved by designed exposure and by treating with various chemicals. Patinas are commonly green, but may vary in colour such as of red, brown, black, blue, or gray. Its surface may be smooth, glossy, or crusty. Newly made objects are deliberately patinated to simulate the antiquity in a process is often called distressing.

640px-miguel_c381ngel_buonarroti27s_pietc3a0_bronze_replica_at_museo_soumaya

Michelangelo’s Pieta in Bronze by Ferdinando Merinelli 1932 > Wikipedia image

Patina over copper alloys, such as bronze, due to the chlorides leads to green, while sulfur compounds are brown. The basic palette for patinas on copper alloys is blue-black due to ammonium sulfide, brown-black with liver of sulfur, blue-green for cupric nitrate, and yellow-brown due to ferric nitrate. For new artefacts accelerated patination carried out by applying chemicals with heat. Colours range from matte sandstone yellow to deep blues, greens, whites, reds and various blacks. Some patina colours are achieved by the mix of pigments and chemicals. The surface is enhanced by waxing, oiling, or other types of lacquers or clear-coats. French sculptor Auguste Rodin used to instruct assistants to urinate over bronzes stored or buried in the yard. A temporary-washable patina, is produced on copper, by the vinegar (acetic acid).

640px-bronze_head_28glyptothek_munich_45729_with_and_without_patina_bunte_gc3b6tter_exhibition

Bronze busts –with and without patina > Wikipedia image by MatthiasKabel

In architecture, metals, like copper, bronze, etc. have been used for a very long time, for wall cladding, door panelling, ceiling tiles, and roof covering. Copper provides excellent corrosion resistance. Copper surfaces form tough oxide-sulfate patina coating that protects underlying copper mass and resists further corrosion. Copper corrosion products are less toxic. Copper sheets have been used in many building to cover rounded domes, and articulated roof surfaces. Architectural copper is, though susceptible to oxidizing acids, heavy-metal salts, alkali, sulfur and nitrogen oxides, ammonia, sulfur and ammonium compounds. Brass, an alloy of copper and zinc, has good resistance to atmospheric corrosion, alkali, and organic acids.

593px-letnitsa_treasure

Thracian plaque > Wikipedia image by Ivorrusev

Metal to metal cladding systems were precursors to Plating technology. Such dual metal structures were created by beating, rolling, rivetting or co-forming. The chief purpose was to add strength to a weaker metal. Forging a metal over metal in some cases created partial homogeneity. It was easier to forge soft metals like tin, lead and copper over harder metals like Bronze, Iron etc. Tin and lead could be softened through heat and used for coating. Metal coating by cladding or sheathing, were useful for corrosion resistance, wear resistance, improved electrical/thermal conductivity and better handling (touch-feel).

640px-kanazawa_gold_factory

Gold foil processing at a workshop in Kanazawa Japan > Wikipedia image by Eckhard Pecher

Some of the simplest methods of sheathing used Gold, Silver and their amalgams with mercury. Gold, Silver, Tin and mercury based amalgams were used as liquidized coatings, where as Silver and Gold were fused as thin sheets or foils. Tin coatings were used for mirror making.

6781143107_d4f8d1f9d9_c

.

WOOD SURFACE FINISHING

WOOD SURFACE FINISHING

Post 472 by Gautam Shah

.

Woods’ surfaces have some inherent qualitative characteristics. These relate primarily to the species of wood, broadly the Softwoods and Hardwoods. Other features include presence of oils or resins, food transfer cells, pores, nature of grains (straight, entwined, interlocked, curly or mottled), and local variations of grain colours. Timbers in spite of good seasoning practices show changes in the wood surface during various seasons, stresses and over long term conduct. Wood products are created from young timbers (freshly seasoned) as well as reuse of aged timbers. Wood finishes, are applied on fresh timbers, for conservation of existing status, and for rejuvenation or reformation exercises.

SAMSUNG DIGITAL CAMERA

Soft-wood knot

Wood finishes are broadly of three classes: 1. Finishing done to timbers, 2. Finishing fashioned after a product or item is formed and 3 Finish processes for repairing or reconditioning an existing product.

Clonfert Cathedral Choir Stalls being Ammonia fumed to darken the colour and enhance grains

1 Finishing done to timbers is accomplished with sizing and shaping operations, and include levelling and straightening of the surface.

2 Finishes fashioned after a product or item is formed, are of two types: Finishing with tools, relating to micro-removal of surface material, by grinding, sandpapering, burnishing, singeing, etc. Finishing, a surface, with applique materials, such as surface sealing, putty application, staining and coating. In some instances it may include covering with film, foil or printing.

3 Finish processes for repairing or reconditioning an existing product may involve full or partial removal of existing applied finishes, re-levelling or straightening of an original timber surface to correct deformation of bending, warping, surface irregularities caused by differential shrinking. The removal of existing applied finish is most difficult as it is a matter of conservation, preservation, correction, all in a very limited scale of intervention.

Soft wood planks

Differential wood grain colour

SOFTWOODS are in dull in colour, light in weight and soft grained, but not always inferior in quality. The sap and heart portions are not very different in colour. Soft woods are easy to finish by planing and sanding. A finished surface exposes the tender portions, the remnants of food transfer areas. And these are likely to shrink and decay over a long period, in spite of seasoning. Small amounts of aliphatic compounds, waxy and resinous substances give a fresh wood, a short lasting, smooth feel and slight sheen. Softwoods due the grain structure and the constituents are difficult to stain. Its surface cannot be well sealed and levelled by chalk or oxide pigments, but a coat of very low viscosity NC Lacquer can seal the face.

Pine wood

Softwood articles are difficult to restore, as the wood grains of aged article show uneven settlement. To correct this, entire applique coating must be removed, and surface re-ground, or heavy surface filling by low opacity minerals is required. Old timber articles show very dry surface, which is prone to chipping along the grain.

HARDWOOD Quebracho colorado wooden sleepers of Argentine origin in Uruguay

 HARDWOODS are darker in colour and heavier in weight. In hard woods, the heart portions are fairly distinguishable from the sap portions. On planing and sanding the hardwood surface, intermittent branches of pores, the food transfer areas are clearly visible. The pores are very narrow in width and short in length. The pores on drying tend to shrink in but being fewer and tightly packed by the surrounding fibres, effect of moisture transfer is not very acute as with soft woods. Hardwoods are tough grained and require greater efforts for smoothing, but the finished surface retains its fairness much longer.

Abies grandis (grand FIR) Trunk section

Rough finishes are cheaper, take less time to prepare and require simple tools and techniques. Some rough surfaces give better bondage to preservatives and coatings. Rough surfaces are good for moisture movement but are highly vulnerable to insect and bacterial growth. Rough finishes hide local defects such as stains, knots, ugly grains, fine cracks etc.

Rough or as sawn finish of Hardwood

Smooth finishes are costly, require fine tools and superior techniques. Smooth finish often give poor bondage to preservatives and coatings but one requires much lesser quantity for coverage. Such finishes collect little dirt. Smooth finishes are not as susceptible to bacterial growth as the rough finishes. The timbers for smooth finish should have a fine grain pattern. Heart portions are much better for smooth finish then sap portions. Sap portions may however be finished fairly smooth, provided are immediately covered with moisture proof coating. Hardwoods usually provide smoother finish and of permanent type then soft woods. Woods with resinous or oily substances generally have smooth feel, however, if the substances are reactive or soluble in water or aliphatic solvents, may create problems during coating. Sisam and rosewood have oily or waxy face, which does not allow oil paints or varnish finish. Such woods need to be covered with very thin coatings based on solvent evaporation drying; like nitro cellulose lacquer. Timber surfaces are flame charred or singed to provide slightly darker to black tone to selected areas. The flame is either ‘cool’ capable of depositing carbon, or `hot’ to singe the surface.

.

MOSAICS

Post 331 –by Gautam Shah

.

640px-Cordoba_moschee_innen5_dome

640px-Madaba_map

Mosaic is a surface assemblage of small pieces flat materials. The assemblage could be unintentional or natural, or a designed product. The designed product may reflect a pattern or a form. The image in mosaic emerges through the variations of textures, a tonal gradation within a colour range, multiplicity of colours and their boundaries, differences of surface reflectivity of the material pieces and most importantly through the flow of joints. The image also comes forth from the composition formed by the joints or spaces between the material pieces. The width, depth (or contour) and colour of the joint spaces could be uniform or varied.

26131980608_b84bf08fdf_z

Rustic_calendar_from_Saint-Romain-en-Gal_(Autumn)

Sumerian Cone Mosaic Pergamonmuseum0116

Historically mosaics have been opaque, translucent or transparent ones, but modern technologies provide vivid mosaics. Vivid mosaics have variable transparencies and adjustable light emanating facilities. The light emanating mosaics have controllable intensities and tonal gradations. The cathode tubes, LCD and LED are examples of mosaic forming screens, but the same could be through a projected image on plain or crystal-activated screens.

Benches_at_Park_Guell_by_Antonio_Gaudi_(4209976058)

Traditional mosaics were patterns and forms created from pieces of stones, ceramics, wood, glass, metals, leather and fabrics. The pieces were fixed to the base surface through a binding or cementing agent. Fabric and leather mosaics are created by stitching together the edges (patch work), whereas metal pieces were joined mechanically or fuse-welded at the edge, or with the base. Mosaic joints expose the base surface, the joining material or additional fill-in material. Mosaics are created by inlaying pieces of materials into a base through chasing, engraving, etc. For inlaying rare materials such as sea shells, precious stones, jewels, pearls, gold and silver etc. are used.

prize-winning-quilt-958633_1280

640px-Roses_over_crossed_canes,_from_Museo_dell'Opificio_delle_Pietre_Dure,_Florence

Li_Jiang_Guesthouse

Romans have used bricks and stone masonry patterns as mosaics. Stone mosaics of Roman and later in Romanesque period exploited the marble debris of old buildings. Wood mosaics are used in floors and as marquetry in furniture and panelings. Ceramic mosaics have been popular everywhere, as the colour range vivid, glossy, permanent (non-fading) and different from any other material finishes. Glass mosaics were technologically closer to ceramics. Glass offered various levels of transparencies. Glass mosaics were created by joining specifically shaped pieces with lead cams. The pieces were coloured during glass manufacturing. The mosaic like effect is now created by painting with stained varnishes, often within marked areas. Mosaics’ patterns are also created by composite formation where fillers like stones, plastics, wood, etc. go into a matrix of a resin. Metal mosaics are created through alloying with a non miscible materials.

770px-Wood_mosaic

bibi-xanom-196898_640

USA-Palo_Alto-Stanford_Memorial_Church-Glass_Window-1

.

SURFACE LEVELLING

Post 291 — by Gautam Shah

.

Surface-levelling is a major category of surface finishing technologies. Surface-levelling is done by THREE major systems, Removal of excess material, Deposition of additional material, and Refashioning the surface sections.

John_Barr_stonemason,_1930

REMOVAL OF EXCESS MATERIAL

To remove the excess material surfaces are re-cut, ground and polished. Stone surfaces are chiselled or axed to level out the surface and to remove the weathered crust. Freshly mined and weathered stones are re-cut or chiselled to expose a fresh surface. Rough cut or split (sedimentary) stones are spliced into two, by a smooth saw cut. Leather surfaces are shaved for thinning and to remove the surface hair. Leathers are split to make uppers and soles. The palm leaves are shaved to remove the stems and make them smoother for writing. Barks of the trees are removed by axes and choppers. Timbers are re-cut or planned with finer tools to achieve a smoother surface. Timbers are split very finely to create veneers.

geograph-5392550-by-Chris-Allen

Johann_Erdmann_Hummel_Das_Schleifen_der_Granitschale_1831

Grinding and Polishing, are the two finer processes for surface-levelling of hard materials such as building stones, metals, glass, and precious and semiprecious gems, ivory, bones, leathers, timbers, pottery products, cement concrete and other cement products. Hard materials such as marble and granite, take a high gloss, whereas others like sand stones, are too coarse-grained to be polished, and can only be smoothed to a granular finish. Surface-levelling is done by sharp tools that chip away very thin section off the surface. Grinding is done by rubbing down with a graded series of coarse and fine abrasives, such as Carborundum, sandstone, emery, pumice, and whiting. Grinding wheels usually consist of particles of a synthetic abrasive, such as silicon carbide or aluminium oxide, mixed with a vitrified or resinoid bonding material. Grinding can be coarse or fine, depending on the size of the grit used in the grinding wheel. Polishing uses extremely fine abrasive substances, such as jewelers’ rouge, Tripoli, whiting, putty powder, and emery dust, to rub or burnish an extremely smooth and glossy finish on the surface of a material. Metal and glass can be ground to a mirror finish. Polishing is done by tumbling and vibratory mass-finishing media, sandblasting, pulp-stones, ball-mills etc. The polishing materials are coated on the surface of cloth, felt, or leather wheels. One special type of polishing wheel is made of soft rubber or plastics with the abrasive grains moulded into it.

4011546989_8fdef11b9a_z

Metal Turning SchlichtenDrehen

Honing and Lapping, are used for very fine level of polishing by material removal process. Honing improves the accuracy and finish of motor car cylinder bores, hydraulic cylinders, and similar parts. There are four types of precision grinding machines: Center-type grinders, Center-less grinders, Internal grinders, and Surface or flat bench grinders.

lawn-1812944_640

Other processes include singeing, washing, bleaching, etching, etc. Textiles, paper leather, leaves, wood, etc. are some of the materials that can be singed. High temperature singeing removes surface fibres or hair, de-oxidize impurities and in case of metal harden the surface. Synthetic or composite textiles are selectively or locally singed to fuse the fibres or filaments, and create transparency, opacity, etc. Wood surfaces on sintered create a dehydrated, old shrivelled, or shrunk surface similar to an old wood. Metal surfaces also burnt to harden the top surface and to remove oily residues, dehydrate, and descale the surface. Reverse of metal plating process removes the surface molecules to achieve matt finish.

DEPOSITION OF MATERIALS

Haircoloring

Deposition of material could be casing, cladding, layering, or lamination, lapping, molecular deposition and coating. Cladding is common in masonry work for a new surface, insulation, water proofing, etc. Casing is done to metal structures for rust inhibition, static discharge and fire protection. Layering or lamination is common in composite formation through co-extrusion processes. Molecular deposition of metal compounds or ceramic forming (non-metal) materials achieve a very thin body deposition. Polyester metalized films offer solar radiation cut-off. Metal plating through anodic transfer also creates very thin body layering. Metal deposition over plastics, ceramics and filaments provide dual qualities. Coating is very vital field of material addition. Coatings are applied in a liquid phase or get converted to it at the time of application (such as in case of powder coatings). Coating deposition is aided by electrical charge, pressure or spluttering. Many of the surface addition processes are intermediary treatments for the next lot of surface treatments. Alkaline or acidic washes or solvent wetting leaves substances that are beneficial for other subsequent applications. In medical field skins, tissues and muscles are planted to encourage fresh growth.Transfiguration_of_Christ_Hajdudorog_FrameSpraying_to_precent_malaria._Vanuatu_2009._Photo-_AusAID_(10722134375)

REFASHIONING THE SURFACE SECTIONS

eggplant_grill_food_bbq_vegetables-696190.jpg!d

two_girls_daughter_matter_hair_care_hair_straightening_hair_straightner_blondie_brunette-1331926.jpg!d

The most important treatments in these sections are annealing and hardening. Heat treatment followed by controlled cooling changes the molecular arrangements within the entire body or surface sections. In case of polymers, chain linking alters the quality of materials. Textiles become de-creased or creased on pressurized with heat treatment. Burnishing of a metal surface achieves a smoother surface, through hard pressing up to yield-point. Woods, papers and Fabrics are burnished to achieve a compacted mass. Surfaces are refashioned by pressing or embossing textures and patterns.

Embossed Armour Italyembossed leatherEmbossed_Postcard,_Carnegie_Library,_Houston,_Texaseuro-items-1807120_640

.

FINISHING of MATERIALS

Post 174 ⇒   by Gautam Shah 

Finishing surface of Pottery

Material finishing processes are employed essentially for changing the surface textural quality, by alteration, removal or addition. The Finishing processes may improve sensorial aspect (touch-feel-texture), look-colour-pattern, adhesion-wettability, weldability-solderability, corrosion resistance, tarnish resistance, chemical resistance, wear resistance, hardness, electrical conductivity, etc. An unfinished surface is often called mill finish. The finishing processes include acid-alkali treatment, chemical reactions, electro chemical deposition-removal (plating), mechanical procedures, burnishing, singeing, washing, coating, plastering, cladding, etc.

Sharpening a Sword

Of these processes GRINDING, POLISHING, HONING, LAPPING AND BUFFING, are briefly described here.

GRINDING

Grinding removes material from the surface to roughen a normally glossy surface like Glass, or polishes a rough surface like Stone. Grinding requires material of higher hardness than the surface material. Grinding is usually a step up or down procedure, using graded series of coarse to fine or fine to course abrasives. The grinding media or abrasives are of many types and forms, such as Carborundum, sandstone, emery, pumice, sand, glass and diamond powders, leather, jute, etc.

Brass polishing -an etching type of surface removal or ‘grinding’

Where a material constitution permits, very fine grinding may polish the surface. Grinding is also a cutting operation, where the material is cut or removed as minute chip, swarf or dust.

Grinding wheels usually consist of particles of a synthetic abrasive, such as silicon carbide or aluminium oxide, mixed with a vitrified or resinoid bonding material. Grinding can be coarse or fine, depending on the size of the grit used in the grinding wheel. Metal and glass can be ground to a mirror finish and an accuracy of 0.0000025 cm. Abrasive are used as grinding wheels, sandpapers, honing stones, polish, cut-off wheels, tumbling and vibratory mass-finishing media, sandblasting, pulp-stones, ball mills, and many other tools and products.

Stone surfaces are chiselled to split the material into thinner sections, to remove the weathered crust and also to level out the surface. Grinding and polishing is done to Hard materials such as building stones, marbles, granites, metals, glass; Precious and Semiprecious stones like gems, diamonds; Animal products like ivory, bones, horns, teeth, leather; Plant products like timbers, seeds; Ceramics like pottery products, bricks, cement concrete and other cement products.

Construction_worker_J2b

Grinding-Finishing a Tri-suction RCC floor

.

POLISHING, HONING, LAPPING, BUFFING

Polishing uses extremely fine abrasive substances, such as jewellers rouge, Tripoli, whiting, putty powder and emery dust to rub or burnish an extremely smooth and brilliant finish on the surface of a material. The polishing materials are coated on the surface of cloth, felt, leather, rubber pr polymer wheels or as belts. Metal surfaces are levelled and finished by honing and lapping. Honing removes less than 0.0125 millimetres of material from the surface to eliminate micro scratches and machine marks from ground machine parts. It is done with bonded abrasive sticks or stones that are mounted in a honing head. Lapping is a process in which a soft cloth (wool, linen and chamois-leather) impregnated with abrasive pastes (rubbing compounds), is rubbed against the surface of a work-piece. Honing and lapping, are essentially metal finishing techniques. Buffing is a term used for polishing of metals. Buffing is done with polishing compounds and brushes of various shapes, and materials, likes: (animal hair, synthetic fibres, plant fibres -coir), flex, wool and leather. Barber polishing the razor on a leather stripe is a buffing process that levels out small nicks on the blade.

Barber’s Razor grinding stone and Honing leather straps

There are four types of precision grinding machines: Centre-type grinders used for tiny valve spools to steel mill roles. Centre-less grinders used for bowling balls, surgical sutures, and tapered roller bearings. Internal grinders are employed for inside diameters of gears, bearing races, and similar parts. Surface grinders are used for die tops, bench surfaces.

Lapping is used to produce a high-quality surface finish or to finish a work-piece within close size limits. Dimensional tolerances of 0.00005 millimetres can be achieved in the hand or machine lapping of precision parts such as gauges or gauge blocks.

.