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.
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
security at 113. If Security
doesn’t answer, hang up and punch 3051 or 3052 for a TTU line in
, press “9” to get off campus, and dial
to reach the Security cell phone. Please
contact the instructor and/or resident artist as well.
Alarm: pull switches are located next to all the major exit doors.|
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.|
flushing supplies are mounted on the wall next to the first aid kit
by the sink in the advanced classroom. |
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. |
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
General Guidelines - There are a few general safety and cleanup
issues that must be considered at all times in the ceramics facility:
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.|
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. |
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. |
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.|
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. |
all clay and glazes off your hands before eating.
No food or drink is permitted in the glaze lab.|
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
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. |
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
stainless steel pugmill that should not be used by anyone unless specifically
cleared by the instructor.
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. |
pugmill is reserved for various custom claybodies, and must be
completely emptied and cleaned after each use.
Because of its open, unprotected hopper, the
is requires special care when using. As
mentioned above, the
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.
the section below on p
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
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
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
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
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.|
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.
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.|
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. |
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
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. |
food or beverages are allowed in the glaze lab, and after handling
glazes or glaze materials, always wash your hands thoroughly before eating
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.
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.|
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.|
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
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.
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
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
security as per the instructions at the beginning of this document.