Vince Pitelka
Appalachian Center for Craft
Tennessee Technological University

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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.  

Tennessee Technological University - Appalachian Center for Craft - Clay Studio

Vince Pitelka, 2006

Safety in the Clay Studio
Equipment Operation and Materials Handling

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 you ever have immediate concerns, contact me or the resident artist at once, and if neither of us is available, contact Craft Center security.  My home and cell phone numbers are on the wall next to my office door. 

In the event of an emergency: use the phone behind the door in the clay room, or if that phone is inaccessible, use the phone in the alcove by the side entrance to the café.  Push 6801 or 6802 for a local line and call 911 to report the emergency, and then call Crafts Center security at 113.  If Security doesn’t answer, hang up and punch 3051 or 3052 for a TTU line in Cookeville , press “9” to get off campus, and dial 267-1086 to reach the Security cell phone.  Please contact the instructor and/or resident artist as well. 

General Information

bulletFire Alarm: pull switches are located next to all the major exit doors.
bulletA 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.
bulletEye-skin flushing supplies are mounted on the wall next to the first aid kit by the sink in the advanced classroom. 
bulletFire Extinguishers: There are three extinguishers - two are mounted next to the big kiln room doors opening to the outside, one on the inside wall, and one on the outside wall. The third is mounted on the wall in the resident artist studio next to the outside door. 
bulletThe 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. 

General Guidelines - There are a few general safety and cleanup issues that must be considered at all times in the ceramics facility:

bulletAvoid 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 fan turned on take the work outside.  When you need to sweep or scrape up dry clay residue from the floor, use a spray bottle and spray a little water over it first - this will keep down the dust.  Always wear your respirator when any dust is present.  See the section below on purchasing a respirator.  If you do not have a 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.
bulletStudents 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. 
bulletWhen cleaning the floors, mist the surface first, sweep up all dust and clay debris, and deposit in the trash cans.  Once that is done, lightly hose down the floor, and then squeegee the dirty water into the floor drains.  If there are no floor drains or if they are sealed off, use the mop and mop bucket to soak up the dirty water.  If there is an accumulation of debris in the bottom of the mop bucket, pour the water off into the sink, and then dump the debris into the trash cans. 
bulletAvoid 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 frequently. 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 deal with any clay, slurry, slip, or glaze that you deposit on the floor.
bulletAlways 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 your wheels to the “off” position when you are done working.  Never leave the clay extruders with the handle sticking out into the room.  Always make sure that kilns are properly shut down when you are through with them, as per the instructions for the particular kiln. On gas kilns, make sure that pilot and main gas valves and the blower controls are in the off position when you shut down the kiln.   
bulletWash all clay and glazes off your hands before eating.  No food or drink is permitted in the glaze lab.
bulletObserve 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 will serve our needs.  Just keep in mind that they close with great 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, and toxic dusts. 

Equipment Operation - Clay Mixers

bulletThe Soldner mixer is the safest clay mixer on the market.  Unlike some other mixers, the Soldner mixer 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. 
bulletThe Estrin clay mixer (the one 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, raku, and terracotta 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. 

bulletThe Bluebird and Venco pugmills are benign and easy to use, but at the same time are potentially one of 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. 
bulletThe Walker pugmill is reserved for various custom claybodies, and must be completely emptied and cleaned after each 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. 

Heavy Lifting - Save Your Back
When moving bags of materials or mixed clay, lift from the legs and not from the spine, and don't attempt more than you are sure you can lift safely.  Most of our dry materials are in 50-pound sacks, but occasionally are in 100-pound sacks, and that is beyond the safe lifting capability of most people.  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.  

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 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 to 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, as this material is heavy and tends 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 and porcelain bodies where flint (silica flour) is a major ingredient.  Sand and grog often contain significant percentages of free silica dust. 

A healthy non-smoker’s lungs can expel clay dust, but do not have the ability to expel fine silica particles.  Instead, they build up 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.  For more information, go to the fact sheet on silicosis at the Centers for Disease Control website.   

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.  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.  For any serious clay studio artisan, smoking is a sure invitation to serious lung problems. 

Whenever working with dry ceramic materials anywhere (except in the spray-booth with the exhaust fan 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.  See the section below on p r. 

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 respirator. 

Whenever adding dry materials to the clay mixer always make sure the exhaust fan is turned on.  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, because you will inevitably be raising dust into the air.  

Purchasing a Respirator
Efficient respirators are available at most good hardware stores and home improvement centers, but generally only in a size that fits the “average” face.  Always make sure that you get a twin-element “half-mask” respirator with a resilient rubber face piece, equipped with P-100 HEPA (high-efficiency particulate air) cartridges or filters 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 firemen wear. 

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.  Many of the respirators sold in hardware stores and home improvement centers are equipped with cartridges for organic vapors, and those are of no use to you unless they also have a P-100 HEPA rating or have additional P-100 dust filters attached to the cartridges.  Also, it is important to be aware that all respirators equipped with organic vapor cartridges must always be stored in a sealed plastic bag when not in use.  If left out, the cartridges are constantly absorbing organic vapors from the atmosphere, and quickly exhaust their usefulness.  Don't get a respirator equipped with cartridges for paint and solvent fumes unless you specifically need protection from those fumes. 

Go to the Lab Safety Supply website for an extensive assortment of high-quality half-mask respirators that come in different sizes to fit your face.  Enter “half mask respirator” in the search box.  They sell the most popular brands used by professionals in industry, including Scott, 3M, MSA, North, Moldex, AOSafety, Survivair, plus their own Lab Safety Supply brand.  Note that some of the masks are available either in standard rubber or in hypoallergenic silicone rubber.  Note also that the mask and the cartridges or filters are sold separately.

Select a small, medium, or large mask depending on the estimated size and shape of your face, and purchase a set of P100 HEPA-rated dust cartridges or filters.  Click on the little orange icon in the upper right that says “quick-view selection guides” to select the appropriate cartridges and filters, and make sure that you get all the required parts.  In some cases you must buy a package of dust filters plus a set of retainer caps to hold the filters on the mask. 

When you receive your respirator, test the face piece for sealing efficiency.  Strap it on your face snugly, hold both hands over the cartridge ports, and try to breathe in.  If there is any leakage around the edges of the mask, then it is a poor fit.  Determine whether it is too large or too small, send it back, and exchange it for the right one. 

Working with Wet Clay

bulletAgain, 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. 
bulletMuscle 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 occurrence 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 de-airing pugmill to do the wedging for you.
bulletSkin 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.  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.    
bulletSafety 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 swung off to the side 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.  When the wheel is not in use always leave the electrical switch in the off position so that it will not suddenly start is someone accidentally steps on the pedal.

Glazing and Glaze-Mixing

bulletOnce 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.  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. 
bulletSkin Irritants present in the glaze lab include soda ash, potassium carbonate (pearl ash), fluorspar, and wood ash.  When wood ash is mixed with water it becomes extremely 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.  Disposable rubber gloves are available in the drawer next to the sink in the glaze room. 
bulletSafety 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 only application method that involves very specific safety precautions is spraying glazes with a spray gun.  All spraying of slips, patinas, or glazes 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.   When you are done spraying, remember to always return leftover glaze to the bucket, thoroughly clean the spray gun canister and nozzle, and sponge off the turntable in the spraybooth.  
bulletNo food or beverages are allowed in the glaze lab, and after handling glazes or glaze materials, always wash your hands thoroughly before eating or drinking.
bulletGrinding Glaze Materials – Other than the ball mill, which involves no particular safety concerns, we do not have equipment for grinding glaze materials.  In the future, if you ever become involved with grinding your own 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 are 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.

bulletDo 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.
bulletDo not ever place your 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 when no visible flame is present.
bulletWhen 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.  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 that appropriate exhaust fans are turned on.  The ventilation system is integral to the electrical switch on the indoor gas kilns, and it is impossible to turn on those kilns without the exhaust fan being on.  The ventilation system for the electric kilns is separate.  Whenever firing an electric kiln, always make sure that the ventilation system is turned on - the switch is to the right of the big frontloader kiln.  Note that whenever you turn the exhaust fan for the indoor kilns, the louvered openings in the wall next to the outside door will open automatically.  This provides the essential make-up air that must be provided whenever any sort of exhaust fan or convection flue is operating indoors.  

A by-product of all bisque firings and (to a lesser degree) glaze firings is sulfur dioxide, which is toxic and corrosive.  Many 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 is highly corrosive. 

bulletAs 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 me or the resident artist as soon as possible.  If you ever have immediate concerns, contact me or the resident artist at once, and if neither of us is available, contact Craft Center security.  My home and cell phone numbers are on the wall next to my office door.  If it is an emergency, always call 911 first, and then contact Craft Center security as per the instructions at the beginning of this document.


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