By Michael McCann, Ph.D., C.I.H., and Angela Babin, M.S.
Many artists work with traditional sculptural materials including plaster, stone, lapidary, clay, wax, and modeling materials. This data sheet will provide hazards and safety information for certain traditional processes. Our data sheets "Ceramics", "Metal Working and Jewelry Hazards", "Plastics" and "Woodworking." have information about other sculptural materials. Plaster
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, which is composed of calcium sulfate. Plaster is mixed by sifting the powder into water. Sometimes salt, potassium sulfate, or potassium alum is added to speed setting, or borax, diluted acetic acid, or burnt lime is added to retard setting of the plaster. Silica sand, vermiculite, sand, and coarse stone can be added to the plaster for textural effects. Wet or dry plaster is carved and modeled with special plaster carving chisels, knives, rasps, and scrapers and other tools.
Hazards 1. 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. 2. 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. 3. 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, and can cause alkali burns. 4. Concentrated acetic acid is highly corrosive by ingestion, inhalation, and skin contact. 5. Burnt lime (calcium oxide) is moderately corrosive by skin contact (especially if the skin is wet), and highly toxic by inhalation or ingestion. 6. Many additives may be hazardous. Silica and vermiculite dust are highly toxic by inhalation, and may cause silicosis. Small amounts are not a major hazard. 7. Careless use and storage of sharp tools can cause accidents. Chipping set plaster can result in eye injuries from flying chips.
Precautions 1. For mixing large amounts of plaster at one time, wear a NIOSH-approved dust mask. Vacuum or mop up plaster dust carefully; do not sweep. 2. Wear gloves and goggles when mixing acetic acid and burnt lime. For large amounts of burnt lime, wear an approved toxic dust mask. 3. When adding hazardous materials to plaster, wear an approved toxic dust mask and clean up dust carefully by wet mopping or vacuuming. 4. 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. 5. Wear ANSI-approved safety goggles when chipping plaster. 6. Store plaster in sealed containers or plastic sealed bags rather than paper bags which can rip open.
Mold releases used with plaster include vaseline, tincture of green soap, auto paste wax-benzine, silicone-grease-benzine, and mineral oil-petroleum jelly. In waste molding, the plaster mold is chipped away.
Hazards 1. Benzine used with many mold releases is moderately toxic by skin contact and inhalation, and is highly toxic by ingestion. It is also flammable. 2. Making plaster casts of hands, legs, and other body parts can be very hazardous due to the heat released during the setting process. Many children and adults have been severely burned doing this.
Precautions 1. Wear gloves and goggles when pouring benzine. Store in safety containers and do not use near open flames or cigarettes. 2. 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.
Plaster can be finished in many ways. It can be painted with paint or powdered pigments, or dyes can be added directly to the plaster mix. Patinas are made by sealing the plaster with shellac or acrylic sprays. They can also be made with a 50/50 mixture of water and white glue, with water-based glue mixed with a 50/50 mixture of lacquer and alcohol, or with bronzing liquids.
Hazards 1. Powdered pigments and dyes are often hazardous by inhalation or ingestion, and in some cases by skin contact. See our data sheet "Art Painting and Drawing" and "Dyeing Safely" for more information on the pigments used to finish plaster. 2. Lacquers contain solvents that are highly toxic by inhalation and moderately toxic by skin contact. Alcohol and shellac are slightly toxic unless the shellac contains moderately toxic methyl alcohol. These solvents are also flammable. Precautions 1. Wear a NIOSH-approved dust mask when using powdered pigments or dyes. Brush or dip dyes or paints rather than spraying. 2. When using solvents, have good general ventilation and wear gloves and goggles. Store solvents safely, and keep them away from open flames and lit cigarettes; dispose of solvent-soaked rags in approved waste disposal cans that are emptied each day.
Stones and Lapidary
Stone carving involves chipping, scraping, fracturing, flaking, crushing, and pulverizing using 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 Soft stones include soapstone (steatite), serpentine, sandstone, African wonderstone, greenstone, sandstone, limestone, alabaster, and several others. Hard Stones 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.
Casting Stones 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. The most common mold is plaster with stearic acid/benzine as the mold release. Portland cement contains calcium, aluminum, iron and magnesium oxides, and about 5% free silica. Some modern cements have acrylic resins in them to give stronger bonding. Sometimes, fiberglass is added as a reinforcement.
Hazards 1. 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. See Table 1. 2. Serpentine, soapstone, and greenstone may contain asbestos, which can cause asbestosis, lung cancer, mesothelioma, and stomach and intestinal cancers. 3. 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.
4. Lifting heavy pieces of stone may cause back injuries. 5. Power tools create larger amounts of fine dust than hand tools. Pneumatic tools can create large amounts of fine silica dust. 6. Pneumatic and electric tools and compressors can create a noise hazard. Temporary hearing loss can become permanent with chronic exposure and noise can also adversely affect the heart, circulation, blood pressure, intestines, and balance.
7. 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. 8. Electrical tools create the potential hazard of electrical shock from improperly grounded or faulty wiring.
9. 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. 10. Acrylic resins are skin irritants and sensitizers. See our data sheet on plastics for more information.
Precautions 1. 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. 2. Wear an NIOSH-approved toxic dust respirator when carving all stones. Particular care should be taken with stones that contain free silica. 3. Techniques to keep down dust levels in the air include daily vacuuming or wet mopping, and use of a water spray over your sculpture when you are carving. Do not dry sweep.
4. 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, wear a face shield. 5. Change clothes and shower after work so as not to track the dust home. Wash your clothes regularly. 6. 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.
7. Use proper lifting techniques (bent knees). 8. Pneumatic and electric carving tools should be equipped with portable exhaust systems. 9. All electric tools should be properly grounded and in good repair. Install ground fault circuit interrupters if machines are within 6 feet of water that can splash.
10. Isolate the compressor far away and shield with sound-absorbing materials. Wear ear protection if necessary. 11. Protect against vibration damage from pneumatic tools by 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. 12. Tie long hair back, and don't wear ties, jewelry, or loose clothing which can get caught by machinery.
13. Equip all grinding wheels, sanding machines, and polishing wheels with local exhaust ventilation, and use wet sanding and polishing techniques whenever possible to keep down dust levels.
Lapidary 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.
Hazards 1. See stone hazards above. 2. 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. 3. Gem cutting machines can create very high noise levels. Precautions 1. See stone precautions above. 2. In the absence of adequate local exhaust ventilation, wear NIOSH-approved toxic dust respirator for sanding, grinding, or polishing operations that create dust. Use wet grinding processes.
Finishing Stone 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. Hazards 1. Grinding and sanding, especially with machines, can create fine dust from the stone being worked on. 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. Precautions 1. In the absence of adequate local exhaust ventilation, wear NIOSH-approved toxic dust respirator for sanding, grinding, or polishing operations that create dust.
Table 1. Not significant or slight hazards: - Very small amounts of free silica in alabaster, amber, bone ash, calcite, carborundum, diamond, dolomite, gypsum, hematite, jade, marble, putty (tin), travertine, whiting, wollastonite.
Containing other moderate to extremely toxic ingredients: - asbestos, carbon black (if contaminated with polycyclic aromatic hydrocarbons), cerium oxide, cerrusite (lead), coal, corundum (aluminum oxide), cryolite, erionite (zeolite), fluorspar, lapis lazuli (ingestion may create hydrogen sulfide), litharge (lead), malachite (copper), serpentine (may contain asbestos), soapstone (talc), talc (can have asbestos-type materials), vermiculite (asbestos), witherite (barium), zirconia (allergen).
Modeling Materials Clay Modeling materials used in sculpture include traditional moist clays, non-hardening modeling clays, self-hardening clays, oven-hardening clays, wax, and papier mache type products. See our data sheet "Ceramics" for more information on clay.
Modeling 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. They are widely used in jewelry and bead-making, and sometimes are inappropriately used by children.
Hazards 1. 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. 2. In the past, many of these materials contained di-(ethylhexyl) phthalate (DEHP), a probable human carcinogen, as a plasticizer. 3. The curing temperatures of different product are not the same, and in some cases, very close to the temperatures at which decomposition can occur.
Precautions 1. 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. 2. Baking any art material in an oven which is also used for food carries the risk of contaminating food. Use a separate oven, that has reliable temperature control and only bake these products to their particular hardening temperature. 3. Obtain the Material Safety Data Sheet (MSDS) from the manufacturer or supplier, and make sure the temperature of decomposition is not reached. 4. Do not use hardening modeling clays that have DEHP as a plasticizer. At this time, the longterm hazards of replacement plasticizers have not been adequately researched. 5. Use these products in front of a window exhaust fan.
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.
Hazards 1. 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.
2. 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.
3. 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).
Precautions 1. 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. 2. 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. 3. Do not use chlorinated synthetic waxes.
This data sheet is adapted from the second edition of Artist Beware, by Michael McCann, Ph.D., C.I.H., 1992