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natural composition and as such. Are highly susceptible to damage under the right conditions other stones acquire salts from the environment such as during burial when they are exposed to groundwater laden with salt or when they are exposed to water that has peculated through natural or man made material such as gypsum or cement that also contains large amounts of salt water also plays a role in the aggressive attack on stone by industrial air pollutants since the th century and to a limited degree well before that the destructive properties of sulfur released when! Fossil fuels are burned have been well documented sulfur reacts in the atmosphere, to form sulfur dioxide which in turn combines with available moisture to form sulfuric acid when in limited edition contact with marble or limestone both of which are calcium carbonates the sulfuric acid transforms the surface of. The stone to gypsum calcium sulfate this transformation has several unfortunate results first the gypsum has greater volume and greater porosity so it will. Hold more acidic water at the surface continuing the acid attack on the underlying stone and encouraging other destructive! Processes such as. Biological activity for example the growth of mold the gypsum crust. Formed often incorporates dark particulate matter from the polluted atmosphere such as carbon resulting in the unsightly black crusts seen on many urban buildings and monuments this crust has a very different response to changes in temperature and will often crack or peel. Away leaving fresh stone exposed to the same destructive cycle biological deterioration, of stone is also a concern root or vine growth can physically fracture marble for example if the root finds its way into a crack or fissure similar to the, way tree roots or weeds can fracture sidewalks or roads direct dissolution of stone, by lichens and ivy is also possible and the presence of such plants leads to the retention of water! Which as aforementioned accelerates other destructive processes in. The past restoration, of stone sculpture involved many aggressive methods aimed at. Erasing or disguising any reproductions damage or loss, due to, age weathering or accident these. Techniques extended to the. Recutting. Of the sculpture or. The reduction of the sculpted surface by means of abrasives or acids to remove damage? Or to improve the aesthetic appearance of the sculpture aesthetic dictates and fashion of the photo particular time in which the restoration was undertaken greatly influenced these choices and often the sculpture became more of a product of the restorer's hand and time rather than a work reflecting the intent of the original artist today sculpture restoration normally limited to the cleaning and repair of major damage is, guided by the various professional codes. Of original ethics such as the code of ethics and guidelines for practice of the american institute for conservation, of historic and artistic works. Aic followed by professional conservators original material and surface are carefully guarded and the conservator takes great care, not to alter, the intent or spirit of the object or influence the way in which it may be interpreted missing areas are often left missing and damage is often repaired fantastic realism. Only if doing so does! Not, require unacceptably invasive treatments that are extensive in nature or that may not be reversible nonetheless when replacing missing segments is acceptable or necessary the conservator does this in such a manner as to make the replacements or additions apparent under close inspection or through using easily available inspection techniques because soluble salts are so aggressively destructive to stone sculpture their removal is of paramount importance if they are present in. Sufficient quantities traditionally, if the object is small enough to be submerged in water that is regularly refreshed salts are soaked out until they are completely removed from the stone however when the sculpture is too large to. Submerge too fragile to soak or secured to a site other methods, must be employed also some stones are composed of minerals, that themselves will readily dissolve after prolonged contact with water in such instances poulticing is. An optional method that avoids prolonged submersion of the stone in water and yet maximizes desalination poulticing involves wetting. The sculpture with water and then placing a clay or paper pulp based material mixed with water on the surface as the water is drawn to the surface of the poultice by evaporation the salts dissolved in the water, are carried along and deposited in the poultice material the poultice is then removed from the stone surface and the process, repeated until all or an acceptable amount of the salts present are removed stone can lose its cohesive, strength when the material that binds. The grains together becomes disrupted or lost through dissolution in such a situation the stone is described as sugary because the individual grains or crystals! Become easily dislodged and have the appearance of loose sugar granules the stone may begin to delaminate in flakelike sections in such cases the cohesive and structural strength of the stone must be reinstated by the introduction of a consolidant the characteristics of good, stone landscape consolidants include long term stability and strength under adverse conditions outdoors the ability to. Penetrate deeply into the stone and provide even distribution of the final consolidating product throughout the stone and a minimal effect upon the appearance of the stone once it is introduced i, e it should not change the colour or other. Characteristics such as translucency or opacity of the stone consolidants can be divided into two major categories mineral and synthetic. Consolidants among the, mineral consolidants are lime water which, is the introduction of a saturated water solution of calcium hydroxide into the matrix of a calcium based stone such as limestone or marble once. The calcium hydroxide is deposited its eventual interaction with atmospheric carbon dioxide forms a network of calcium carbonate, similar to that which makes up the stone itself in a similar manner the application of alkoxy silanes in recent decades offers the conservator a method! By which amorphous silica can be introduced as a. Binder and strengthener for deteriorated sandstone some silanes will also impart water repellency to the stone synthetic polymer, based consolidants include acrylic polymers epoxies and polyesters although these are. A considerable improvement over past materials, such as wax and, natural resins some have proved unsuitable in certain environments and. Over long periods of exposure some epoxies have altered over a relatively short period of time and dramatically changed the appearance of the sculpture while other synthetic consolidants have proved unable to penetrate deeply enough into the stone and their application has resulted in a thin dense and impermeable, crust that falls, away owing to the buildup of salts or water vapour behind it a variety of coatings ranging from natural resins to waxes have been used for famous ists the protection of stone sculpture from either the outdoor elements or the. Deposition of dust and grime within the indoor environment acrylic polymers are now, more commonly used for the less demanding environments whereas surface consolidants and water repellents based. On silicone materials or hydrophobic silanes are often used for sculptures placed outdoors surface coatings can function to repel unwanted deposits or, to serve as sacrificial layers that when removed during regular maintenance carry the deposits with them cleaning was once undertaken. With relatively aggressive methods such as abrasives acids and even. Chisels to remove the offending deposits or stains more often than not these approaches resulted in considerable damage to? The original sculpted surface at the turn. Of the, st century the professional conservator aggressively guards against any loss of original surface even to the point of accepting the presence of a deposit or stain rather than endangering the original material of the sculpture in some cases the deposits that are obscuring the detail or subtle, carving on the surface are in themselves informative and important and must be, preserved rather. Than removed in the case of many archaeological artifacts or ethnographic objects for example minute amounts of preserved material such as traces of pigment or deposits from original use can shed a great deal of light on the. Original appearance of the sculpture its history function method of manufacture and to a degree the artist's intent nouveau contemporary techniques of cleaning may range from simple mechanical removal of the deposit with a common soft eraser, to the use of surgical scalpels often with the aid of a binocular microscope for more cautious and delicate cleaning small, scale. Power tools are commonly used when the deposit is extremely hard—for, example dental ultrasonic descalers can be used to remove hard calcite or silica realism visionary online landscapebased deposits or residues of modern cement and grout the conservator sometimes. Employs microair abrasive equipment that uses fine particulate powders such as walnut shell or talc the technique requires that the operator have considerable experience and skill so that the stone surface itself is not abraded chemical agents such as surfactants agents that reduce surface tension between a liquid and a solid chelates agents that form! Compounds with metal ions making them more easy to remove or solvents can also be used either in local application using a small cotton swab or mixed, in a poultice just as poulticing works as a means of desalination it also can be used to eliminate deposits and stains poulticing material may include clays such as sepiolite a! Magnesium. Trisilicate clay paper pulp or gel materials such as carboxymethylcellulose steam cleaning and water misting sometimes called nebulization are museum of modern, also often employed in the cleaning process though like all the techniques already mentioned they must be cautiously applied, to ensure that only the desired deposit or grime is removed without damaging the stone surface or other decorative elements first used in the s to, clean the black pollution crusts from stone architectural sculpture laser technology. Has rapidly developed as a promising method for cleaning stone surfaces laser energy dislodges or vaporizes the offending material that is normally, of a darker colour than. The stone the laser has, become one of the most promising tools for future use in conservation, due to. The advancement of more commonly available! Units visionary a relative drop in cost of the equipment. And a greater familiarity with laser technology in the field of conservation metal sculpture metal sculpture ranges from solid cast statuettes of the ancient near east to the massive steel public monuments of the late th century in most instances the deterioration of metal sculpture is due to the reversion of the metal to a more stable mineral state in the case of iron the process is most commonly known as rusting and results in a red brown powdery mineral iron oxide copper and its alloys most commonly alter to the green or blue carbonates of copper malachite or azurite or to the red oxide mineral cuprite copper and? Its. Alloys may also quickly corrode in the presence of chloride by the cyclic process called bronze disease during which copper is altered to copper chloride a powdery white blue product silver tarnishes rapidly even in the presence of minute, amounts of sulfur and lead will quickly corrode in the presence of acetic acid common to all of the processes is the presence of water which is needed to initiate and complete the corrosion of the base metal to a more voluminous and less cohesive, mineral product in the past. The treatment of metal sculptures often involved completely stripping the surface until it was free of all corrosion product or alteration abrasive techniques such as sandblasting or microbead blasting were regularly. Used as was chemical stripping which dissolved the mineral alteration products and electrochemical reduction which also stripped the surface. Of any corrosion products and of patina the term usually given to corrosion products that are either naturally occurring or artificially formed on the metal surface, patinas are valued for aesthetic beauty and for the authenticity that they lend the object. Today treatment of metal sculptures is far more conservative than in the past although sculpture may be polished as in the case of silver sculpture. That has been tarnished or stripped of its alteration patina. As in the case of some monumental outdoor sculptures alteration products are carefully evaluated for their importance and authenticity before their removal is considered and patinas are far more often protected than removed. Any treatment that results in the reshaping, of the metal, or in any irreversible addition such as soldering or welding to secure broken segments is, now considered with great? Caution at the turn of the st century the conservator's main intervention in the process of corrosion involved providing a more benign environment usually meaning as dry as possible and as free of harmful pollutants as possible and maintaining the sculpture's stability through a series of preventive maintenance, procedures such as regular cleaning and the application of protective coatings regular maintenance has. Proved to be. Giclee highly cost effective and successful in the preservation of outdoor sculpture over the. Long term regular cleaning and coating with waxes or synthetic polymers or both which sometimes contain corrosion inhibitors have kept corrosion, processes in check even in aggressive and polluted urban environments. In some. Cases however the! Conservator's only option is to recommend that the sculptures be removed from the outdoor environment placed in a. Protected area and replaced by a replica made of a more resistant material although cleaning of metal sculpture can include, the total removal of all, corrosion products including those termed and valued as patina a more conservative approach continues to develop within the field which recognizes the value of naturally occurring, change to the metal surface in the case of archaeological material and, ethnographic sculpture the corrosion products may hold remnants of original surface treatments or remains of associated materials or evidence of use this evidence must be carefully studied and a. Full understanding of the sculpture's importance now and in the future must be weighed against its loss by. Cleaning wood sculpture although relatively little wood sculpture survives from prehistorical and early historical, periods an enormous amount of sculpture was produced in the last millennium particularly the polychrome sculptures of western european religious devotion and those of india china japan and other asian nations wood is a very open and porous structure the bulk of which is water absorbed! Or chemically bound to. Its thin walled. Structural cells like, many plant materials wood responds to changes in, the humidity of its surrounding environment taking up available water. To reach equilibrium with the environment or conversely giving up. Water if the surrounding air. Is dryer dimensional changes to the wood occur when this exchange takes place as wood takes up water it will swell as it loses water it will shrink sometimes dramatically both actions induce considerable stresses, on the structure of the wood resulting in irreversible. Warping or complete splitting. Of the wood section additionally the physical. Strain placed on the structure by continual expansion and contraction weakens the wood or, may cause further serious damage. To wood already weakened by insect attack or age when decorated with paint wood will respond to heat and moisture with greater movement destroying the bond between the wood and, the less elastic paint and ground preparation resulting in the painted decoration's flaking away from the surface wood can also be a food source or a nesting place for a variety of insects such as wood boring beetles termites and grubs infestation can be so severe that the sculpture loses all of its structural strength and collapses wood can also be damaged by a variety of fungi and bacteria with similar results the predominant concern. Regarding the, preservation of wood is the control of the environment exposure to, light particularly the ultraviolet and shorter wavelengths of the visible spectrum results in both the chemical and physical alteration of all organic material including wood wood can become darker or lighter or lose its structural integrity through the. Action of light energy, acting as. A catalyst for other chemical reactions appropriate and stable temperature and humidity levels and an environment low in ultraviolet radiation illumination and pollutants. Can ensure the slowing of any. Deterioration regular dusting and general maintenance of the sculpture as well as! Vigilant actions to keep damaging insects away are also paramount when intervention is necessary with wood sculpture it normally involves some form of. Consolidation either of the wood sculpture's structure or of its decorative surface. The range of consolidants for each of these actions is broad including synthetic acrylic polymers. Organic based natural resins and animal, glues jerry c podanyj h larson decorative arts furniture a small amount of furniture, from ancient civilizations has been! Preserved in extreme environments such as the dry desert of, egypt or the water logged soils of england these surviving pieces have proved that the craft of furniture making has remained relatively consistent for centuries if a piece of furniture is equilibrated to a moist environment and then put in a dryer? One as in the case of, centrally heated homes. Of modern times it will lose moisture and shrink boards and! Segments will warp and those restricted from movement will crack and even digital split veneers thin, wood panels placed over the surface of the structure of the furniture may lift crack and separate, from the underlying structure high humidity performing will result in many of the same problems and also encourage mold and the decomposition of fabric leather or other skins the various metal fittings particularly iron may also corrode high humidity will also encourage the decomposition of the glue in, most traditional furniture arty this would be animal or fish based glues through the action of microorganisms light is also a problem in that the visible spectrum especially the ultraviolet aspect will bleach fade or discolour the wood light may also alter any additional decorative elements for example marquetry on th and th century furniture is often stained with plant dyes that rapidly deteriorate fade when exposed to light. Exposure to? Light will also cause leather skins and, most upholstery to deteriorate more rapidly indoor and outdoor urban and industrial pollution will deteriorate metal fittings wood. And upholstery fabric if the furniture is made, of wood, the, finish of the wood can function, as both a decorative and a protective layer, the coating may also act as a barrier to either retain moisture in. The wood or. Prevent the wood from absorbing additional moisture finishes are realism often natural resins such as sandarac or mastic that are contained in. Waxes or, solvent waxes or drying oils such as linseed, oil may also be used alone, furniture can be painted with a. Wide variety of pigments bound in wax encaustic or in organic binders of oils or. Gums. Lacquer which was first developed in china and then imported to europe is manufactured by the application of specially treated tree sap the conservation treatment and restoration of furniture today, is a, mixture, of traditional crafts and modern scientific investigation on photographs a basic level the conservator tries to keep objects at optimum and stable values of relative, humidity—between and percent—year round with little change avoiding any abrupt or extreme changes in humidity or temperature the conservator will avoid exposing the object to strong light or light sources with high ultraviolet content such as many types of fluorescent tubes and will. Avoid localized heating through radiators, or strong lights, in close proximity to the. Object a regular, inspection for insect attack is of paramount importance repair. And. Stabilization of furniture may range from the simple repair of a small crack or lost area. Of gilding to stabilization of a major joint complete reupholstering refinishing or the design and manufacture of alternate structural supports whatever the degree of intervention the art? Conservator increasingly seeks out materials and methodologies that both respect the original material and condition of the piece of furniture and ensure reversibility of the added materials glass and other vitreous, materials since ancient times glass has been. Used for both decorative and everyday use glass glaze enamel and faience—the four vitreous products—are manufactured from three basic components silica alkali and small amounts of calcium glass glazes and enamel but not faience contain high amounts of alkali, such as sodium oxide soda glass or potassium, oxide potash, glass generally speaking the mechanisms, that are, involved in the deterioration of glass are identical for all. Vitreous materials although a wide variety of agents are art involved inherent susceptibility to deterioration plays an important role composition is crucial because it will determine how susceptible the glass is to various agents and processes of. Deterioration for example roman period soda lime silica glass is quite durable while medieval window. Glass is highly unstable due to its large content of potash from beech wood ash lime is also unstable glass deteriorates quickly in an alkaline environment due to the breakdown of the silica network of all the agents in fantasy the environment that are aggressively damaging, to glass none is, more. Directly or, indirectly destructive than water water especially when it mixes with pollution products becomes acidic has a low ph and extracts, the alkali from the silica network of the glass the alkali modifiers are leached from the glass structure and brought to the surface where they attract and absorb more water this buildup of moisture on the surface can often be seen as small droplets the glass can. Also have a slippery feel in either case the glass is then? Said |