Section 14: Sculpture
Many artists work with traditional sculptural materials including plaster, stone, lapidary, clay, wax, and modeling materials. See ceramics for information on some other sculpting media.
Plaster and Plaster Molds
Plaster can be carved, modeled, and casted. Varieties of plaster include: Plaster of Paris, casting plaster, white art plaster, molding plaster, and Hydrocal. These are all varieties of calcined gypsum, composed of calcium sulfate. Mold releases used with plaster include vaseline, tincture of green soap, auto paste wax-benzene, silicone-grease- benzine, and mineral oil-petroleum jelly. In waste molding, the plaster mold is chipped away.
- Plaster dust (calcium sulfate) is slightly irritating to the eyes and respiratory system. In situations where there is heavy inhalation of the dust, more severe respiratory problems can result.
- Potassium sulfate and potassium alum are slightly toxic by ingestion; potassium alum is slightly toxic by skin contact, and can cause mild irritation or allergies in some people.
- Borax is moderately toxic by ingestion, by inhalation, and by absorption through burns or other skin injuries. It is also slightly toxic by skin contact, causing alkali burns.
- Concentrated acetic acid is highly corrosive by ingestion, inhalation, and skin contact.
- Burnt lime (calcium oxide) is moderately corrosive by skin contact (especially if the skin is wet), and highly toxic by inhalation or ingestion.
- Careless use and storage of sharp tools can cause accidents. Chipping set plaster can result in eye injuries from flying chips.
- Benzene used with many mold releases is moderately toxic by skin contact and inhalation, and is highly toxic by ingestion. It is also flammable.
- Making plaster casts of hands, legs, and other body parts can be very hazardous due to the heat released during the setting process.
- Wear gloves and goggles when mixing acetic acid and burnt lime.
- Always carve or cut in a direction away from you, and keep hands behind the tool. If the tool falls, don't try to catch it.
- Wear safety goggles when chipping plaster.
- Wear gloves and goggles when pouring benzene. Store in safety containers and do not use near open flames.
- Do not use plaster for body part casts. Instead, use a plaster-impregnated bandage (such as Johnson and Johnson's Pariscraft), along with vaseline or similar mold release as protection.
Stones and Lapidary
Stone carving involves chipping, scraping, fracturing, flaking, crushing, and pulverizing with a wide variety of tools. Soft stones can be worked with manual tools whereas hard stones require crushing and pulverizing with electric and pneumatic tools. Crushed stone can also be used in casting procedures.
Soft stones include soapstone (steatite), serpentine, sandstone, African wonderstone, greenstone, sandstone, limestone, alabaster, and several others. Hard stones include granite and marble. Electric tools include saws, drills, grinders, and sanders, and pneumatic tools include rotohammers, drills, and other tools powered by compressed air. Stone casts can be made using Portland cement, sand, and crushed stone. Marble dust is often used with this technique. Cast concrete sculptures can also be made using sand and Portland cement. Lapidary involves cutting and carving semiprecious stones and has similar risks as hard stone carving. Stones carved include garnet, jasper, jade, agate, travertine, opal, turquoise and many others.
Stones can be finished by grinding, sanding, and polishing, by either hand or with machines. Polishing can use a variety of materials, depending on the hardness of the stone being polished. Polishing materials include carborundum (silicon carbide), corundum (alumina), diamond dust, pumice, putty powder (tin oxide), rouge (iron oxide), tripoli (silica), and cerium oxide.
- Sandstone, soapstone, and granite are highly toxic by inhalation because they contain large amounts of free silica. Limestone, containing small amounts of free silica, is less hazardous.
- Serpentine, soapstone, and greenstone may contain asbestos, which can cause asbestosis, lung cancer, mesothelioma, and stomach and intestinal cancers.
- During chipping and other carving, flying chips and pieces of rock may cause eye injury. Grinding and sanding can release small pieces of stone and dust which are hazardous to the eyes.
- Lifting heavy pieces of stone may cause back injuries.
- Power tools create larger amounts of fine dust than hand tools. Pneumatic tools can create large amounts of fine silica dust.
- Vibration from pneumatic equipment can cause Raynaud's phenomenon, ("white fingers" or "dead fingers") a circulation disease. The hazard is greater with exposure to cold, (e.g. the air blast from pneumatic tools). This temporary condition can spread to the whole hand and cause permanent damage.
- Calcium oxide in Portland cement is highly corrosive to the eyes and respiratory tract, and is moderately corrosive to the skin. Allergic dermatitis can also occur due to chromium contaminants in the cement. The silica in the cement is also highly toxic by inhalation. Lung problems from inhalation of Portland cement include emphysema, bronchitis, and fibrosis.Acrylic resins are skin irritants and sensitizers.
- The dust from quartz gemstones such as agate, amethyst, onyx, and jasper is highly toxic because they are made of silica. Other gemstones such as turquoise and garnet may be contaminated with substantial amounts of free silica. Opal is made of amorphous silica, which is slightly toxic by inhalation.
- Grinding and sanding, especially with machines can create fine dust from the stone which is being worked. There are also inhalation hazards from grinding wheel dust (especially sandstone wheels). Some polishing materials such as tripoli are highly toxic if inhaled in powder form.
- Do not use stones which may contain asbestos unless you are certain that your particular pieces are asbestos free. New York soapstones may contain asbestos, whereas Vermont soapstones are usually asbestos free. Alabaster is a substitute.
- Wear chipping goggles to protect against flying particles; wear protective shoes to protect against falling stones. Wear approved safety goggles when grinding, sanding, or polishing. For heavy grinding also wear a face shield.
- When using carving tools, keep your hands behind the tools, and carve or cut in a direction away from you. Don't try to catch falling tools.
- Use proper lifting techniques (bent knees).
- Protect against vibration damage from pneumatic tools by measures such as having comfortable hand grips, directing the air blast away from your hands, keeping hands warm, taking frequent work breaks, and using preventive medical measures such as massage and exercises.
- Tie long hair back, and don't wear ties, jewelry, or loose clothing which can get caught by machinery.
See Section 12 for information about clay compounds. Modeling clays of the plasticine type usually contain China clay in an oil and petrolatum base. Additives are often present, including dyes, sulfur dioxide, vegetable oils, aluminum silicate, preservatives, and turpentine. These are modeled and carved with simple tools. There are also a variety of polymer clays that are self- hardening, or oven-hardening (e.g. FIMO, Sculpey), which are not really clays at all. These are often based on polyvinyl chloride.
- Some of the additives in plasticine clays such as turpentine and preservatives might cause skin irritation or allergies, and sulfur dioxide might cause some respiratory problems in certain asthmatics. The amounts present are usually small.
- The curing temperatures of different product are not the same, and in some cases, very close to the temperatures at which decomposition can occur.
- Use gloves or apply a barrier cream to hands if skin irritation results from using plasticine modeling clays. Wash hands with soap and water after contact.
- Obtain the Material Safety Data Sheet (MSDS) from the manufacturer or supplier, and make sure the temperature of decomposition is not reached.
Many different types of waxes are used for modeling, carving, and casting. These include beeswax, ceresin, carnauba, tallow, paraffin, and micro-crystalline wax. In addition there are the synthetic chlorinated waxes. Solvents used to dissolve various waxes include alcohol, acetone, benzine, turpentine, ether, and carbon tetrachloride. Waxes are often softened for carving or modeling by heating in a double boiler or with a light bulb, by sculpting with tools warmed over an alcohol lamp, or by the use of soldering irons, alcohol lamps, and blowpipes. Wax can be melted for casting in a double boiler. Additives used with waxes include rosin, dyes, petroleum jelly, mineral oil, and many solvents.
- Overheating wax can result in the release of flammable wax vapors, as well as in the decomposition of the wax to release acrolein fumes and other decomposition products which are highly irritating by inhalation. Explosions have occurred from heating wax that contained water.
- Alcohol and acetone are slightly toxic solvents by skin contact and inhalation; benzine and turpentine are moderately toxic by skin contact, inhalation, and ingestion. Carbon tetrachloride is extremely toxic, possibly causing liver cancer and severe liver damage, even from small exposures. Exposure to carbon tetrachloride can be fatal by skin absorption or inhalation.
- Chlorinated synthetic waxes are highly toxic by skin contact and skin absorption, causing a severe form of acne (chloracne). Some may be contaminated with polychlorinated biphenyls (PCBs), which are highly toxic, causing chloracne, liver problems, and possibly cancer of the pancreas and melanoma (a fatal form of skin cancer).
- Do not overheat waxes. Use a double boiler and a temperature-controlled hot plate, or a crock pot. Do not use an open flame to melt waxes.
- Use the least hazardous solvent to dissolve your wax. Do not use carbon tetrachloride under any circumstances. Store solvents safely, do not smoke or have open flames near solvents. Dispose of solvent-soaked rags in an approved waste disposal container which is emptied daily.
- Do not use chlorinated synthetic waxes.
Wood sculpture uses a large number of different types of hard and soft woods, including many exotic tropical woods. Many of these woods are hazardous themselves. Sometimes woods are treated with hazardous preservatives or pesticides.
- Saps present in many green woods, and lichens and liverworts present on the surface of freshly cut wood, can cause skin allergies and irritation from direct contact.
- Many hardwood dusts, especially those from exotic woods, are common sensitizers and can cause allergic skin reactions. Some hardwoods can cause allergic reactions in individuals working with or using finished hardwoods. Softwoods do not cause as high a frequency of skin and respiratory problems as do hardwoods. A few individuals can develop allergic reactions to some softwoods.
- Contact with the dust of many hardwoods can cause conjunctivitis (eye inflammation), hay fever, asthma, coughing, and other respiratory diseases. Canadian and Western Red Cedar are examples.
- Some hardwoods can cause hypersensitivity pneumonia (alveolitis), and frequent attacks can cause permanent lung scarring (fibrosis). Examples of these highly toxic woods include giant sequoia, cork oak, some maple woods and redwood.
- Some hardwoods contain chemicals that are toxic, and can cause a variety of symptoms, including headaches, salivation, thirst, giddiness, nausea, irregular heartbeat, etc. A classic example is hemlock.
- Inhalation of hardwood dust is associated with a particular type of nasal and nasal sinus cancer (adenocarcinoma). This type of cancer has a latency period of 40-45 years, and occurs to the extent of about 7 in 10,000 among woodworkers who are heavily exposed. This rate is many times higher than the rate of nasal adenocarcinoma in the general population. Over half of all known cases of this type of cancer are found in woodworkers.
- Whenever possible, use common hardwoods rather than rare tropical hardwoods.
- If you have a history of allergies, you should avoid common sensitizing woods.
- If you are handling woods that can cause skin irritation or allergies, wear gloves.
Plywood and Composition Board
Plywood is made by gluing thin sheets of wood together with either urea-formaldehyde glues (for indoor use) or phenol-formaldehyde glues (for outdoor use). Composition board, for example particle board, is made by gluing wood dust, chips, etc. together with urea-formaldehyde resins. The materials can emit unreacted formaldehyde for some years after manufacture, with composition board emitting more formaldehyde. In addition, heating these materials or machining them can cause decomposition of the glue to release formaldehyde.
- Formaldehyde is highly toxic by inhalation, highly toxic by eye contact and ingestion, and moderately toxic by skin contact. It is an irritant and strong sensitizer. Formaldehyde is a probable human carcinogen. Even trace amounts of free formaldehyde may cause allergic reactions in people who are already sensitized to it.
- Machining, sanding, or excessive heating of plywood or composition board can cause decomposition releasing formaldehyde, carbon monoxide, hydrogen cyanide (in the case of amino resins) and phenol (in the case of phenol-formaldehyde resins).
- Use low-formaldehyde products whenever possible. There are particle boards that are made without formaldehyde, but these are very expensive.
- Do not store large amounts of plywood or composition board in the shop since it will emit formaldehyde. Instead store in a ventilated area where people do not work.
Wood Preservation and Other Treatments
Pesticides and preservatives are often applied to wood when it is being timbered, processed or shipped. Unfortunately, it is hard to find out what chemicals, if any, have been added. This is especially a problem with imported woods, since pesticides and wood preservatives banned in the United States and Canada are often used in other countries. Pentachlorophenol and its salts, creosote, and chromated copper arsenate (CCA) have been banned for sale in the United Sates as wood preservatives because of their extreme hazards. They can, however, still be found in older woods and chromated copper arsenate is still allowed as a commercial treatment (e.g. "green" lumber, playground equipment, and other outdoor uses). It is supposed to be labeled. A variety of other chemicals can be used in treating wood including fire retardants, bleaches, etc.
- Pentachlorophenol is highly toxic by all routes of entry. It can be absorbed through the skin, cause chloracne (a severe form of acne) and liver damage, and is a probable human carcinogen and reproductive toxin.
- Chromated copper arsenate is extremely toxic by inhalation and ingestion, and highly toxic by skin contact. It is a known human carcinogen and teratogen. Skin contact can cause skin irritation and allergies, skin thickening and loss of skin pigmentation, ulceration, and skin cancer. Inhalation can cause respiratory irritation, and skin, lung and liver cancer. Inhalation or ingestion may cause digestive disturbances, liver damage, peripheral nervous system damage, and kidney and blood damage. Acute ingestion may be fatal.
- Creosote has a tarry look, and is also used for outdoor wood. It is a strong skin and respiratory irritant, and is a probable human carcinogen and teratogen.
- Zinc and copper naphthenate are slight skin irritants; copper naphthenate is moderately toxic by ingestion. If suspended in solvents, the solvent would be the main hazard.
- Obtain Material Safety Data Sheets on all chemicals being used in wood treatment. Treated wood itself does not have Material Safety Data Sheets, so you have to try and find out about any treatments from the supplier. In the United States, CCA-treated wood is required to have a label and information on safe handling.
- Do not handle woods that have been treated with pentachlorophenol or creosote. Avoid scrap or old woods of unknown origin.
- If you add wood preservatives yourself, use zinc or copper naphthenates, if possible.
- Do not burn wood that has been treated with creosote, pentachlorophenol or chromated copper arsenate.
Carving and Machining Wood
Woods can be hand carved with chisels, rasps, files, hand saws, sandpaper, and the like, or they can be machined with electric saws, sanders, drills, lathes and other woodworking machines.
- Woodworking machinery and tools also present physical hazards from accidents. Machinery accidents are often due to missing machine guards, faulty equipment, or using the wrong type of machine for a particular operation. Tool accidents are often caused by dull tools or improper use.
- Vibrating tools, for example chain saws, can cause "white fingers" (Raynaud's phenomenon) involving numbness of the fingers and hands. This can lead to permanent damage.
- Electrical equipment can also present electrical shock and fire hazards from faulty or inadequate wiring.
- Sawdust and wood are fire hazards. In addition, fine sawdust is an explosion hazard if enclosed.
- Wear goggles when using machines that create dust. For lathes and similar machines which may produce wood chips, use a face shield and goggles, and make sure the machines are properly shielded.
- Be sure that all woodworking machines are equipped with proper guards to prevent accidents. Use the proper machine for particular operations and repair defective machines immediately. Do not wear ties, long loose hair, loose sleeves, necklaces, long earrings or other items that could catch in the machinery.
- Keep hand tools sharpened, and cut away from your body. Do not place your hands in front of the tool.
A variety of glues are used for laminating and joining wood. These include contact adhesives, casein glue, epoxy glues, formaldehyde-resin glues (e.g., formaldehyde-resorcinol), hide glues, and white glue (polyvinyl acetate emulsion), and the cyanoacrylate "instant" glues.
- Epoxy glues: These are moderately toxic by skin and eye contact, and by inhalation. Amine hardeners (as well as other types of hardeners) can cause skin allergies and irritation in a high percentage of the people using them. Inhalation can cause asthma and other lung problems.
- Cyanoacrylate glues: These are moderately toxic by skin or eye contact. They can glue the skin together or glue the skin and other materials together, sometimes requiring surgical separation. Eye contact can cause severe eye irritation. Their long term hazards are not well studied, especially with respect to inhalation.
- Formaldehyde-resin glues: Resorcinol-formaldehyde and urea-formaldehyde glues are highly toxic by eye contact and by inhalation, and moderately toxic by skin contact. The formaldehyde can cause skin and respiratory irritation and allergies, and is a known human carcinogen. The resin components may also cause irritation. Even when cured, any unreacted formaldehyde may cause skin irritation and sanding may cause decomposition of the glue to release formaldehyde. Formaldehyde can be a problem when working with fiber-board and plywood.
- Contact adhesives: Extremely flammable contact adhesives contain hexane, which is highly toxic by chronic inhalation, causing peripheral nerve damage. Other solvents in contact adhesives are mineral spirits or naphtha, and 1,1,1-trichloroethane (methyl chloroform), which are moderately toxic by skin contact, inhalation and ingestion.
- Water-based glues: Water-based contact adhesives, casein glues, hide glues, white glue (polyvinyl acetate), and other water-based adhesives are slightly toxic by skin contact, and not significantly or only slightly toxic by inhalation or ingestion.
- Dry casein glues: These are highly toxic by inhalation or ingestion, and moderately toxic by skin contact since they often contain large amounts of sodium fluoride and strong alkalis.
- Avoid formaldehyde resin glues because of allergic reactions and the carcinogenicity of formaldehyde.
- Use water-based glues rather than solvent-type glues whenever possible.
- Wear gloves or barrier creams when using epoxy glues, solvent-based adhesives, or formaldehyde-resin glues.