Much of the following information is specific to the clay studio at the Appalachian Center for Craft, but should still provide useful for any studio artist working in clay.
Click HERE to access a PDF copy of this information.
Tennessee Technological University – Appalachian Center for Craft – Clay Studio
Vince Pitelka, 2016
Safety in the ACC Clay Studio
Whenever you have questions or concerns about safety or toxicity in the clay studio, see me or the resident artist as soon as possible. If they are serious or immediate concerns, contact me or the resident artist at once, and if neither of us is available, contact Craft Center security. My cell is 931/260-3323 and is also on the wall next to my office door.
In the event of an emergency: Call 911 immediately. If possible use a land-line so that you get hooked directly to DeKalb County 911. Use the phone behind the door in the clay-mixing room, or if that phone is inaccessible, use the phone in the alcove by the side entrance to the café. Press “9” for an outside DeKalb County line and dial 911 to report the emergency, and then call Crafts Center security – again, “9” for an outside line, and then call 1-931/267-1086 to reach the Security cell phone. Whoever is working security should have the phone on their person. Immediately after that, contact the instructor and the resident artist as well. If I am not here, call my cell at 931/260-3323.
- Fire Alarm pull switches are located next to all the major exit doors.
- A first aid kit is located in the advanced classroom next to the sink. If any supplies are low or missing please notify the instructor or the resident artist.
- Eye-skin flushing supplies are mounted on the wall next to the first aid kit by the sink in the advanced classroom.
- Fire Extinguishers are mounted just inside the main outside exit doors for the intro and advanced classrooms, the kiln room, the glaze room, and the resident artist studio. There is also a fire extinguisher mounted outside the kiln room door next to the brick saw.
- The gas master valve is located next to the gas meter on the outside wall next to the door to the intro/throwing studio. There are two valves, and either one will shut off the gas to the whole building. This will shut down all of the gas kilns inside and outside the building, so don’t do it unless you think there is a significant safety problem. The valves are on when the handle is in-line with pipe, and off when the handle is 90 degrees to the pipe.
Safety Issues in the Clay Studio
With reasonable precautions the clay studio is a very safe place to work, but in order to maintain a safe environment you must familiarize yourself with the key issues in ceramic studio safety. Some of the issues discussed below are of primary concern to intermediate and advanced students and professional ceramicists, but there are fundamental precautions that must become second nature to every person working in the clay studio, as they affect not only your own personal safety, but everyone else’s as well.
There are a few general safety and cleanup considerations that must be implemented at all times in the ceramics facility:
- Avoid making dust! Don’t leave clay scraps on the floor. Don’t leave ware-boards where they might fall over and raise a cloud of dust. Confine all dust-producing processes to the spray booth with its exhaust fan turned or under the flexible exhaust nozzles in the glaze room with that exhaust fan turned on, or take the work outside and wear a proper respirator. Whenever you need to sweep or scrape up dry clay residue from the floor, use a spray bottle and very lightly mist water over it first – the slightest amount of moisture will keep down the dust. Always wear a proper twin-element respirator when any dust is present in the air. If you do not have a proper respirator, leave the area when there is any dust in the air and do not return until all dust has cleared. As a general practice, you should always avoid breathing dust of any kind. All of it is harmful.
- Heavy Lifting – Save Your Back – When moving bags of materials or moist clay, lift from the legs and hips and not from the spine, and don’t attempt more than you are sure you can lift safely. Our dry materials are all in 50-pound sacks, but that may be beyond your own safe lifting capability. If so, get help. When you need to move quantities of dry materials or mixed clay, always use the hand truck or one of the four-wheel platform carts.
- Clean up clay debris. Students at the advanced level are responsible for keeping their individual studio areas clean. You must realize that clay debris on the floor in your studio means that everyone else is breathing the dust produced when you work in your studio, and that is not acceptable. Having such generous individual studio space in a BFA program is very unusual, and you must earn this privilege by taking very good care of the space.
- When cleaning the floors, always lightly mist the surface first, sweep up all dust and clay debris, and deposit in the trash cans. Mist the floors even if you are wearing your respirator, because without misting, dust is being raised into the air and is settling on all surfaces. Once you have swept or scraped up the dust and loose debris, lightly hose down the floor, and then squeegee the dirty water into the floor drains. If there are no floor drains, squeegee to a central area and use the wet mop to remove all excess water and squeeze the mop into the dedicated mop bucket. If there is an accumulation of debris in the bottom of the mop bucket, pour the water into the sink and then dump the debris into the trash.
- Avoid any accumulations of water on the floor, especially where clay residue is present (except when cleaning the floors, of course). The combination of water and clay residue produces a very slick, slippery mud. The floors in the advanced classroom and the peripheral studio spaces are the responsibility of the students working in those spaces, and must be cleaned regularly. The floors in the glaze room and the intro/wheel room are cleaned on a regular basis, but between cleanings it is your responsibility to clean up any clay, slurry, slip, or glaze that you deposit on the floor.
- Always leave machinery/equipment in the correct “shut down” mode, so that it cannot start abruptly and so that no parts are protruding that could cause physical injury. Turn pottery wheels to the “off” position when not in use. Never leave the clay extruders with the handle sticking out into the room. Always make sure that kilns are properly shut down when you finish using them, as per the instructions for the particular kiln. On all gas kilns except the Norman updraft, make sure that pilot and main gas valves (and the blower controls on the downdraft) are in the off position when you shut down the kiln. On the Norman updraft shut the red-handled shutoff valve to the burners, but leave the green shutoff valve open so that the pilots remain lit.
- Wash all clay and glazes off your hands before eating. No food is permitted in the glaze lab.
- The swinging doors – observe normal “rules of the road” protocol when using the double swinging doors at either end of the kiln room. No matter what direction you are approaching from, always go through the door on the right, and watch carefully to stay out of the way and keep other people out of the way when the doors are swinging shut. These self-closing fire doors are required by fire codes, and no other design would serve our needs. They close with considerable force and you do not want to be in the way.
During the clay mixing process there are three primary concerns: equipment operation, heavy lifting (discussed above), and toxic dusts.
Equipment Operation – Clay Mixers
- The Soldner mixer is the safest clay mixer on the market. Unlike some other mixers, the Soldner will not operate unless the lid is closed. Water and dry materials can be added through the grate opening in the lid while the machine is running. Recessed beneath the rotating concrete drum is a large chain sprocket with a roller chain driven by a small drive sprocket on the gearmotor under a metal cover at the back of the machine. There is no danger of becoming entangled in this chain when you are working around the front of the machine, but the chain and sprocket are coated with a thick lubricant, so it is good to be aware of their presence and keep hands and feet away from the chain and sprocket.
- The Estrin clay mixer (to the left of the Soldner) is a less efficient machine, and should not be used unless you have a very specific reason and have cleared it with the instructor or the resident artist.
We have three pugmills. The main workhorse for most stoneware and earthenware claybodies is the Bluebird non-deairing mill located next to the clay cage gate in the clay-mixing room. The Venco deairing pugmill is located in the clay cage and is reserved exclusively for porcelain claybodies. In the back corner of the clay-mixing room is an old Walker stainless steel pugmill that should not be used by anyone unless specifically cleared by the instructor or resident artist.
- The Bluebird and Venco pugmills are easy to use safely, but at the same time are potentially the most dangerous machines in the clay studio. A pugmill is similar to a large horizontal meat grinder, and the analogy is appropriate. Pugmills are slow-turning and quiet, but extremely powerful. When operating the pugmill, under no circumstance does your hand or any tool ever get below the top of the hopper opening. When the pugmills are operating properly, you can simply toss lumps of clay into the hopper, and the auger will consume them. If the clay backs up at all, use the attached plunger to force the clay down into the hopper. When you need to clean the mill, turn off the main switch and the disconnect switch on the wall for the Bluebird mill, and unplug the Venco mill. Don’t ever take any chances with a pugmill. They are almost unstoppable and have no conscience.
- The Walker pugmill is reserved for various custom claybodies, and must be completely emptied and cleaned after every use. Because of its open, unprotected hopper, the Walker is requires special care when using. As mentioned above, the Walker can be used only with permission and guidance from the instructor or resident artist.
Toxic Dust – Always Avoid Breathing Dust
Although there are some pieces of equipment that can cause immediate and possibly catastrophic injury, the greatest long-term hazard in the clay studio is dust. All ceramic materials that come in dry, powdered form present an inhalation risk, and you must always protect yourself from the dust. The primary concern is silica (quartz, flint) dust, which is composed of very fine sharp-edged particles. Fine particulate free silica (pure silica particles that are not chemically combined within other materials) is contained in some of the component materials we use in claybodies. Most secondary clays (those that have been transported by wind or water) contain very little free silica because silica particles are heavy in comparison to clay and tend to settle out. Primary clays like kaolins often contain small percentages of free silica as an impurity. The greatest danger is in mixing high-fire stoneware or porcelain bodies where powdered flint (silica flour) is sometimes added as a major ingredient. Sand and grog often contain significant percentages of free silica dust.
While you should never breathe dust of any kind, a healthy non-smoker’s lungs can expel clay dust and the coarser silica particles, but do not have the ability to expel the finest silica particles. Instead, they build nodules of scar tissue around each particle. The effect is cumulative, and long term inhalation of significant quantities of silica dust results in silicosis (potter’s rot, black lung, etc.), which is ultimately fatal.
Smoking damages the cilia in the lungs. Cilia are small hair-like organs that line the interior surface of the lungs. They function by moving foreign substances up into the bronchial passages, where they are expelled by coughing. If you have ever been in a smoky environment and afterward coughed up dirty-looking mucous, it is because the cilia are doing their job. The function of the cilia is damaged by smoking, decreasing their ability to move foreign substances, especially insoluble dusts, which simply accumulate in the lungs, interfering with proper breathing, eventually causing emphysema and/or other lung diseases. Every serious clay studio artisan must be aware that smoking will drastically increase your risk of serious lung damage including silicosis.
Whenever working with dry ceramic materials anywhere (except in the spray-booth with the exhaust fan on or under the moveable suction nozzles in the glaze room with that exhaust fan turned on) always wear an approved twin element respirator with appropriate cartridges or filters for ultra-fine dust, and with a resilient rubber face piece that seals effectively against your face. Even when using the moveable vacuum nozzles in the glaze-mixing area it is a very good idea to wear a respirator. See the section below on respirators.
NOTE: Disposable paper-element dust masks should never be used in the clay studio. Do not ever put yourself in any situation where there is dust in the air unless you are wearing an appropriate twin-element respirator.
Whenever adding dry materials to the clay mixer always make sure the exhaust fan is turned on and wear your respirator. This fan is the noisiest machine in the place, so you only want it running when it is needed. It’s noisy because it’s really doing its job, so don’t ever add dry materials without the fan turned on. Once all the dry materials are wet, you can turn off the fan, but keep your dust mask on as long as you are moving around in the clay mixing room or materials warehouse (the cage), because you will inevitably be raising dust into the air.
Purchasing a Proper Respirator
Proper respirators are available at most good hardware stores and home improvement centers, but beware of the ones including organic chemical cartridges that you don’t need. Also, those models generally come in one size that fits the average-size face. Always make sure that you get a twin-element half-mask or half-facepiece respirator with a resilient rubber face piece, equipped with P-100 HEPA (high-efficiency particulate air) dust filter designed to protect you from very fine dust. Half-mask means that it covers your mouth and nose, but not your eyes, as compared to a full-mask respirator with oxygen supply such as firefighters use.
A respirator appropriate for the ceramic studio does not need to have a cartridge for organic vapors from solvents, paints, etc., unless you specifically need that protection. As mentioned, many of the respirators sold in hardware stores and home improvement centers are equipped with such a cartridge, and those respirators are of no use to us unless the cartridges also have a P-100 HEPA rating or have additional P-100 dust filters attached. Also, be aware that all respirators equipped with organic vapor cartridges must be stored in a sealed plastic bag when not in use. If left out, the cartridges are constantly absorbing minute amounts of organic vapors from the atmosphere and will quickly exhaust their usefulness. This is a real problem, because people run the risk of assuming they are being protected from organic vapors when the organic cartridges are spent.
Got to amazon.com and enter “3M 6000 Series Half Facepiece Respirator” in the search box. This is a very good general-purpose dust mask with replaceable twin-element P-100 filters, and cost less than twenty bucks. Note that it comes in small, medium, and large, so get the size appropriate for your face. For more specialized respirators such as hypoallergenic silicone rubber, go to www.lss.com (Lab Safety Supply) for an extensive assortment of high-quality half-mask respirators. You’ll pay a lot more at Lab Safety Supply, especially since the mask and the cartridges or filters are sold separately.
Working with Wet Clay
- Again, Don’t Breathe Dust – Dust ceases to be a factor as long as clay is wet, but even with wet clay it is essential that you maintain good habits regarding studio cleanliness in order to avoid circumstances where dust is created. Whenever possible, minimize dust by cleaning up clay scraps or debris while they are still damp. As mentioned above, when cleaning up dry scraps or other clay debris, mist lightly with a spray bottle before scraping or sweeping to keep down the dust, and wear your respirator.
- Muscle and Joint Problems – A serious concern for everyone working in clay is the long-term effect on the muscles and joints. Of special concern is the wedging process, which contributes to the likelihood of Carpal Tunnel Syndrome, a condition resulting from constriction of nerves and blood vessels by the tendons that encircle the wrist. It is wise to avoid or minimize repetitive muscular movements. If you do all your wedging by hand, switch back and forth between cylinder wedging, right-hand cone wedging, and left-hand cone wedging. Better yet, get a vacuum de-airing pugmill to do the wedging for you.
- Skin Problems – When working with clay, especially when throwing, some degree of dry-skin issues are almost inevitable. Most routine dry skin problems can be addressed with frequent use of a good skin moisturizer, and there are usually bottles of moisturizer around the sinks in the studio. I also have a bottle of good moisturizer on my cart. For more serious dry skin, use a skin protectant (like Eucerin) before working with clay, and a good skin moisturizer immediately afterwards and frequently between sessions working with clay. If dry skin or rashes are more serious or persistent, consult your physician and suggest a referral to a dermatologist.
- Safety with Slab Roller and Potter’s Wheels – When using clay-working machinery such as the slab roller or potter’s wheel exercise appropriate caution. Keep fingers out of the way when operating the slab roller. After using and cleaning the extruder, always leave the handle off to the side against the wall where no one will run into it. When working on the wheel, remove any loose-hanging scarves, ribbons, strings, or ties, and fasten long hair to eliminate any chance of it becoming entangled in the wheelhead. Never leave your cutoff wire or needle tool within the splash-pan. When the wheel is not in use always leave the electrical switch in the off position so that it will not suddenly start if someone accidentally steps on the pedal.
Glazing and Glaze-Mixing
- Once Again, Don’t Breathe Dust. The greatest hazards in the glaze lab are encountered in mixing dry ingredients, and in spraying liquid glazes. All ceramic materials are toxic in inhalation to varying degrees, and silica, talc, barium carbonate, fluorspar, chrome, copper, manganese, and nickel compounds are especially toxic in inhalation. When mixing glazes, place one of the moveable suction nozzles above the gram scale, and the other one just above the glaze bucket on the floor. It is a very good idea to also wear a proper twin-element respirator whenever mixing glazes or slips. Any operation producing significant amounts of dust should be conducted in the spray booth or under the moveable suction nozzles.
- Skin Irritants include potassium dichromate, soda ash, potassium carbonate (pearl ash), fluorspar, and wood ash. When wood ash is mixed with water it becomes highly alkaline, capable of causing skin irritation and even chemical burns. If you experience skin dryness or irritation use a good skin protectant (like Eucerin) as mentioned above, and in the case of wood ash glazes, rubber gloves are recommended.
- Safety of Different Glaze Application Methods – In the glazing process, dipping, pouring, and brushing are all very safe methods, but reasonable precautions should to be taken to avoid prolonged contact with the skin. The most dangerous application method is spraying, which must always be done in the spray-booth with the fan turned on. Before attempting to spray glazes for the first time, always get proper instruction from the instructor or resident artist, and read the handout on use of the gravity feed HVLP sprayguns.
- No food or beverages in the glaze lab. After handling glazes or glaze materials, always wash your hands thoroughly before eating or drinking.
- Grinding Glaze Materials – Other than the ball mill, which involves no safety concerns, we do not have equipment for grinding glaze materials. In the future, if you have access to equipment for grinding glaze materials, you must take adequate precautions to deal with the dust. Quantity grinding of minerals without adequate dust-reclamation equipment is usually illegal, and appropriate grinding and dust collection machinery is extremely expensive.
Kilns and Firing
This section is of concern to everyone. Intro students will not be firing the big gas or electric kilns, but when kilns are firing it is impossible to resist checking them out. With reasonable precautions that is not a problem. The following rules always apply.
- Insulated leather welding gloves are available in the green cart in the kiln room. Always wear proper gloves whenever touching or handling hot surfaces or objects. If any of the gloves are in unusable condition, please turn them over to the instructor or resident artist and we will replace them.
- When firing gas kilns, it is okay to leave the kiln overnight for the preheat period with the burners set quite low. Otherwise, you must be here (or delegate someone else to watch the kiln) during the primary firing period as you turn the kiln up and reach maturation temperature. This is particularly critical at times when the studio is otherwise vacant. No kiln or firing process is completely predictable, and unexpected things can happen. You must be here to respond to those things.
- Do not ever assume that a kiln is cold just because it is not on. Air convection over the surface may reduce radiated heat, and yet the surface may still be hot enough to burn you.
- Never place your unprotected hands or face close to any kiln opening. Positive pressure within the kiln may create a powerful stream of superheated gasses at any opening, capable of inflicting serious burns even if there is no visible flame.
- When you need to look into a kiln to check atmosphere or cones always wear appropriate tinted face shield, goggles, or safety glasses (shade #1.7 to 3.0) to protect your eyes from the extreme brightness and the possibility of heated gases or particles exiting the spyholes. Goggles for gas-welding are appropriate, while those for arc-welding are far too dark. If you see spots before your eyes after turning away from the spyhole, your eye protection is inadequate. You can always find appropriate tinted safety glasses in the green cart in the kiln room that also contains leather welding gloves. Do not neglect proper eye protection. There are well-known older potters who have become partially or completely blind as a result of looking into kilns without proper eye protection.
- All firing processes produce toxic fumes that must be properly vented. When using the indoor kilns, always make sure the appropriate exhaust fans are turned on. The ventilation system is integral to the electrical switch on the indoor gas kilns, and those kilns cannot be operated without the fan on. The ventilation system for the electric kilns is separate. Whenever firing an electric kiln, always make sure that the vent system is turned on – the switch is to the right of the big blue frontloader kiln. A by-product of all bisque firings and (to a lesser degree) glaze firings is sulfur dioxide, which is toxic and corrosive and smells like rotten eggs. Some metals and metallic oxides release highly toxic fumes in midrange and high-temperature glaze firings. Fuel-burning kilns (oil, wood, gas) produce extreme heat and carbon monoxide in the flue gasses, and must be exhausted to the outside through appropriate high-temperature flues. The salt- and soda-firing processes produces hydrogen chloride gas, which is an irritant and highly corrosive.
- As a general rule, do not ever make adjustments on someone else’s kiln unless there is a genuine danger of injury to yourself or others or of damage to the kiln or the studio. When in doubt always ask the instructor, the resident artist, or an advanced student.
Once again, whenever you have questions or concerns about safety or toxicity in the clay studio, see the instructor or the resident artist as soon as possible. If you ever have immediate concerns, contact the instructor or the resident artist at once, and if neither of us is available, contact Craft Center security as explained at the beginning of this document. My cell number is on the wall next to my office door. If it is an emergency, use a land line if possible to get connected directly to DeKalb County 911. Dial 9 from an on-campus phone and call 911 first and then contact Craft Center security as per the instructions at the beginning of this document, and finally contact the instructor and artist-in-residence.
We have a very good record of safety in the clay studio because we take the above guidelines very seriously and always work towards studio safety in all areas. You are all required to follow all of the above guidelines. If you ever see anyone else doing anything you feel to be unsafe, do the responsible thing and immediately contact the instructor or the resident artist.