Cadmium

Cadmium
Used as a pigment in glazes. Can cause respiratory
diseases, osteoporosis, cancer and other problems.
For more information, see Article on Cadmium!

Keep your people safe

Keep your people safe
Keep hazardous material under supervision and away from children and untrained personnel. Always keep hazardous and toxic materials in their appropriate workspace. Do not move them into a situation that would allow them to become a hazard.

Gum Arabic

Gum Arabic
may cause asthma and eye inflammations.

Toxic Material list

Toxic Elements
Silica: Sources- Quartz flint, frits, feldspars clays and glazes
Vanadium: Sources- vanadium pentoxide and ceramic colours.
Cadmium and selenium: Sources- ceramic colours and glazes
Lead: Sources-Lead oxide, frits and glazes
Chromium: Sources- Chrome oxide and some ceramic colours( greens)
Copper: Sources- copper oxide, carbonate and some ceramic colours
Zinc: Sources- zinc oxide, some ceramic colours
Borax: Sources- borax frits

Kaolin also see silica

Kaolin
similar to silica.

Eyes

Wear welding goggles when looking into a
glowing kiln, otherwise eye cataracts will develop
over the years.

Asbestos

Asbestos is calcium magnesium silicate. Since the danger of asbestosis has been recognised (silicosis), asbestos has been completely phased out and replaced by ceramic fibre. Old kilns might still have asbestos as door seals and electric element tail packing.

Health and safety data sheets

Health and safety data sheets.
When purchasing ceramic material, request individual health and safety data sheets. These will enable you to assess any risk and apply any control measures that may be needed.

Handling Toxic Materials

Hands should be washed immediately and
thoroughly after handling glaze materials and any
other toxic minerals.

Footwear

Open footwear, eg. sandals, etc, are inadequate.
Full protection is needed for your feet.

Asbestos

Asbestos: causes particularly nasty fibrosis if inhaled.

Gas kiln ignition

Never ignite a gas kiln without opening the door a
short way first. Accumulated gas can ignite and
explode. Opening the door allows igniting gas to
escape.

Toxic materials

What materials are toxic?
The two materials that are proven toxic at this time are lead and cadmium. Lead is used to make glazes flow better at low temperatures. Cadmium is used primarily to create bright orange and red colors. There are other materials which may be toxic, but there is not enough evidence that they are unsafe at this time, so they are not regulated. Many of these materials are safe in low doses (for example, nickel, barium, selenium and cobalt), but toxic in high doses. So reducing leaching as much as possible is always a good idea.

Raku OH&S: Sawdust

Raku OH&S: Sawdust
Always dampen the sawdust to prevent excessive flame and lessen the risk of airborne burning particles.

Potassium

Potassium,Dichromate/Bichromate
is very poisonous. Can cause kidney failure and is
cancerous. Not recommended for tableware!

Dust

Dusts in all forms in the studio should be avoided. They accumulate over the years and cause emphysema, not a nice disease to have. Take special care with silica.

Raku OH&S: water plunging

Raku OH&S: water plunging
Don't drop enclosed or narrow-necked forms abruptly into water, they will explode.

First Aid kit

First Aid Kit, safety clothing, eye protection, gloves, etc.
should be easily accessible.

Floors

Floors should be kept clean. Clean up spilt clay,
slip and water and other materials immediately.

Vanadium Pentoxide

Vanadium Pentoxide
can cause Anemia; it a respiratory irritant.Uranium Compounds
cause kidney damage, not to mention the radioactivity.
For more information on Vanadium Pentoxide, Please see the Article: "Vanadium Pentoxide"

Silica

Silica
is ever present in clay materials. Repeated inhalation will cause potentially fatal silicosis, or ´potters´ asthma´, a form emphysema. The molecule (especially when fired) has a ´hook´ which attaches itself to the lung wall and accumulates and irritates.

Nickel Oxide

Nickel Oxide
can cause cancer. Will cause skin irritation (´nickel
itch´). Will penetrate skin.

Manganese

Manganese can lead to brain damage and eventually death. Will penetrate skin.
For more information, please see Articles: "Manganese"

Gases

Gases
from salt kilns and reducing kilns, can cause respiration trouble or even acid corrosion of lung tissue.

Cobalt

Cobalt Oxide,Carbonate
can cause liver damage and dermatitis. Will enter the
body through the skin.

Carbon Monoxide

Carbon Monoxide
combines in the body with the hemoglobin in the
blood and reduces the availability of oxygen to the
body. Symptoms such as headache, dizziness and apathy are present in people when 10% of their
hemoglobin combines with carbon monoxide.

Test for alkaline resistance

Ability to withstand alkaline dishwashing detergents. To test this, mix 50 grams of soda ash in 1 liter of water in a stainless steel pan. Bring to boil. Reduce heat to a simmer. Place samples in the pan, cover, and simmer for 6 hours. Compare the color and surface gloss to a similar but untested sample.

Kiln shelves

Never brush a kiln shelf with bare hands. Jagged
pieces of glaze or grit stick to the shelf and can
easily tear the skin.

Plaster Storage/Use

Areas set aside for plaster work should be
cleaned thoroughly after use. Buckets and other
materials used for this work should be for plaster
work only, minimizing the possibility of foreign
mattter fouling up clay.

Material Storage

Materials should be stored in a dry place. The large wheeled airtight bins are great for this, and your back!
Plaster should be set aside from these materials.

Occupational Health and Safety

Like being careful with glazes, occupational health and safety is important when firing, when using various materials, when using toxic components or when using the Raku technique. Learn about OH&S tips and techniques at ceramics.lifetips.com.

Testing for toxicity

Testing for toxicity:
Toxic or hazardous materials can also be ingested by the contamination of food by toxic metals released from fired ware. Pottery for domestic use should be tested for metal release and conform to British Standard: 4800 parts 1&2 (Part 2 is for cooking only). Most pottery suppliers will arrange for this test to be carried out.

Kiln vents

Kiln vents assist greatly in simplifying firing and reducing firing defects. In addition, they improve element life by removing damaging fumes quickly. Of course, if you are firing in a structure where people are working or living, a vent is required to remove the harmful fumes from the area. This is true for bisque firing as well as glaze firing.

Raku OH&S: Before leaving the site

Raku OH&S: Before leaving the site
Thoroughly douse the sawdust-reduction chamber and check the kiln before leaving the site after firing to prevent further smouldering or burning.

Auto cut-offs/failsafes

Auto cut off and failsafes are preferable and
should be checked periodically.

Powercord extensions

Powercord extensions
Avoid use of extension cords where they may
intersect areas where traffic is most likely.

Iron Chromate

Iron Chromate
May lead to acute pneumonia and cause lung cancer.

Using dry ingredients

Make sure you wear a good dust mask when working with dry ingredients. Clay dust from greenware or from glaze components can get into the lungs and over the years cause emphysema. Whenever possible, wet mop your working area; never sweep with a broom, as this throws dust up into the air, which you might breath in.

Lifting

Extreme care should be exercised when lifting
heavy articles. It is essential for the studio potter to be aware of correct lifting techniques otherwise
physical damage is inevitable. A trolley should be
used if nescessary.

Benches

Arrangement of benches, bins, storage areas,
etc., should allow maximum freedom of movement.

Raku OH&S: Kiln area

Raku OH&S: Kiln area
Ensure that the area around the kiln is clear of debris

Mica,/Muscovite,Vermiculite

Mica, Muscovite,
Vermiculite,
may contain traces of asbestos. Inhalation of dust will
lead to lung irritation, possibly cancer.

Lithium

Lithium
very toxic. Not recommended for tableware.

Ceramic materials

Ceramic Materials.
When working with ceramic material, avoid creating dust: Some materials are toxic and can quickly have very serious effects upon health, while less hazardous material can still accumulate over a period of time and cause equally serious health problems. Materials in powder form can be inhaled, and materials can also be absorbed through ingestion from contaminated food, cigarettes and drink. Always wash your hands thoroughly on leaving the workshop, and avoid eating, drinking and smoking in the workshop.

Provide Safety gear

Provide Safety gear
Provide control measures for the processes you are undertaking- clothing, masks, extraction systems and washing facilities. Maintain all equipment and have it serviced and checked for effectiveness.

Raku OH&S: Turning off the gas

Always turn your off gas at the cylinder. To empty the pipe of gas; guard the pipe to prevent the possibility of burning matter dropping onto it.

Toxicity in pre-fired form

Toxicity in pre-fired form (liquid or dry)
Commercial glaze manufacturers label their glazes using ASTM D-4236. All their glazes are either AP Non-toxic, which means non-toxic in liquid or dry form, or CL Cautions Required, which means it has proper labeling of ingredients for health and safety. In this sense, non-toxic only refers to lead and cadmium.
All glazes sold in K-12 schools must be AP Non-toxic. This is to reduce the risk of harm if a child drinks the glaze. You don´t want a lead based glaze in the classroom for example. You will see the AP Non-toxic label on the glaze bottle; a circle with an AP inside.
Remember, all glazes in DRY form are unsafe for breathing, and you should use a good mask whenever dealing with dry glazes. There are chemicals such as manganese which are known to be a health hazard when breathed in dry form, but are not believed to be a problem after being fired. And even clay particles with no toxicity get trapped inside lungs and thus are bad for potters to breathe.

Handling dry ingredients

Dealing with raw materials
Once measured out, powdered materials should be made into slop form immediately.

Ventilation

A well ventilated area in the immediate vicinity
of the kiln is mandatory; in fact it is best to have
kilns of all types outside the main studio area thus
eliminating the risk of poisoning yourself with carbon
monoxide, unburnt gas, sulphurous gases, etc., emitted
especially during reduction.

Electrical appliances

Never turn off electrical appliances with wet
hands especially in combination with water on the
floor.

Fire extinguishers

Fire extinguishers should be placed in an
accessible position near the studio. If a fire
developes in the studio and you are keeping a fire
extinguisher there, the heat may prevent you from
reaching it.

clothing

Loose clothing which may accidentally find its
way into operating machinery should also be avoided.
Similarly with long hair -- as above.

Magnesium Oxide

Magnesium Oxide
is considered inoxious, but general rules for dusts still apply.

Iron Oxide Dust

Iron Oxide Dust
is poisonous for children and can cause "iron
pigmentation" of the lungs, supposedly benign but
contentious.

Cleaning the workshop

Cleaning the workshop
Adopt wet working and cleaning methods to avoid the creation of airborne dust. All surfaces tools and boards should be washed immediately after use.

Food and drink

Food and drink is best consumed outside the
studio or in an area where contamination by
chemicals, dust in the air, etc., is minimal.

Power accessibility

Accessibility of power and light switches: keep
switches and electrical cables away from water or if
this cannot be avoided sufficient protection against
contact should be made.

Uranium Compounds

Uranium Compounds
cause kidney damage, not to mention the radioactivity.

Copper

Copper
Salts are irritants to the skin, eyes, and mucous
membranes. Inhalation of copper dust and fume results
in irritation of the respiratory tract.
For more information on copper and its effects, Please see Article "Copper"

Wedging

Incorrect methods of wedging large pieces of
clay may cause injuries, especially to the back.
Damage may occur after a period of several years.
When wedging you should be well aware of your
capabilities of lifting a piece of clay, remembering
that this weight has to be maneouvered at least 21
times before it is wedged. Back and stomach muscles
are strained if the weight is too heavy. Secondly, the
hands should be released from the piece of clay on
the downward movement, just before it makes contact
with its other half, otherwise the sudden curtailing of
momentum at table level creates jarring tremor which
is transferred through the body via the hands, the
latter of which acts as a lever and jerks the spine.

Talc/Tin Oxide

Talc/Tin Oxide

can result in ´stannosis´, supposedly a benign
condition.

Testing for thermal shock resistance

Ability to withstand thermal shock. This does not mean that you can place a ceramic pan over a flame, or directly into a hot oven. It is very difficult to make pieces that can go directly over flames, and not something an individual should attempt. Ceramic casseroles, etc. should be put into the oven at room temperature, and brought up to temperature slowly. However, your customers might not know this, and even if you tell them, they probably won´t remember. To test for thermal shock, place a test pot in the freezer for several hours. Then submerge the piece in a pot of boiling water. (Alternately, put the pot in the sink and pour the boiling water into it.) Repeat this 3 times, looking for minute crazing on the glaze. It is also a good idea to do what a customer would do. Take a completed piece out of the refrigerator, and put it into an already heated oven. Make sure the piece does not crack.

To test microwave safety

Ability to go from the dishwasher to the microwave. Metal overglazes should never go in the microwave, so it is a good idea to keep them off mugs and other dinnerware items. Other than that, the problem with microwaves is if there is any water trapped inside the clay, it will expand in the microwave and cause the piece to crack. Low fire clays are porous by nature, and always problematic in the microwave. If your glaze is fit very tightly (can withstand the thermal shock test with no crazing), then the glaze may prevent water from getting into the clay, and this will be ok in the microwave. High fire clays should be fired to vitrification to keep water out. (See Tip 17 for more information about vitrification.)
To test microwave safety, take a piece (such as a mug or bowl) and immerse in a pan of water. Bring the water to a boil, then simmer for a few hours. This will allow the piece to absorb water. Then put the piece in the microwave. (The piece should be empty, and you should also put a separate mug of water in the microwave to protect the microwave.) Heat the microwave on high in 10 second increments. After each 10 seconds, carefully touch the piece to see if it is hot. If it has absorbed water, it will heat up. This tells you the piece is not dishwasher safe. You can stop the test when the water in the second mug is boiling.

Resistance to abrasion

Resistance to abrasion (does it scratch easily with silverware?). You can test this yourself. It is usually a problem more with matt glazes than shiny.

Raku OH&S: Foot-ware

Raku OH&S: Foot-ware
Wear strong footwear in case you drop red-hot objects.

Spraying OH&S

Spraying OH&S
Never spray any ceramic material outside an adequate extraction booth; ensure the filter is clean and extraction is effective (it should be checked regularly). Wear a mask and protective clothing.

Selenium

Selenium
affects the liver.

Ferrous Sulphite

Ferrous Sulphite
can be fatal and should be avoided.
Fiber Blanket
especially in the fired state can shed invisible floating fibres that have similar effects to asbestos.

Test for acid resistance

Ability to handle acidic foods. To test for acid resistance, slightly squeeze a slice of lemon to get the juices flowing, and leave the whole slice on the glaze overnight. See if the color changes. If it does, there is some leaching going on. A customer could run into this same color change, and there may be chemicals leaking out. Another way to test this is to put a sample in vinegar for 3 days. Finally, there is lab testing, described later.

Toxicity: Dinnerware

Safe for Dinnerware Use
This is what most potters are interested in. Can you use a certain glaze on a piece which will contain food and beverages?
Toxicity is one aspect of this. If there is no lead or cadmium in your glaze (including no Frits which contain lead), and your kiln is not contaminated with lead, then you pass one toxicity test (for lead and cadmium). (If you have fired leaded glazes before, your kiln brick may have absorbed lead and could be depositing it on current firings. You can get an inexpensive kit at the hardware store to test your kiln for lead release. And of course you should never fire dinnerware in a kiln with other leaded glazes.)
There are some glazes that have lead or cadmium and still say they are dinnerware safe. They have been fired and tested, and found to pass the test for lead and cadmium release. (A small amount of leaching is allowed by law.) There are also some glazes where the cadmium is encapsulated in other glaze ingredients which traps it when fired. The only caution here is that your firing conditions will be different, so it is possible that your pieces could leach when the test pieces did not. For this reason, it is best to have a sample tested anytime you use glazes which contain lead or cadmium. Later on I will tell you how to do that.
Any time you begin to layer glazes, you are pretty much on your own. Any testing that the manufacturer did will not be applicable. If you don´t use any glazes with lead or cadmium as ingredients, you are pretty safe (with the caveats above.) Otherwise, test!
Many potters believe that you should never use these ingredients in dinnerware period. Who knows what may happen to the glaze after years of use, after going through the dishwasher 30 times, after the glazes craze, after they are microwaved and frozen and bombarded with acidic food. It is always possible that a piece will leach lead or cadmium at some point in the future. So to be safe, just avoid them.
Then of course there are the ingredients which are not regulated, but may be toxic especially in high amounts. Unfortunately there is no simple answer to this problem. If you are producing dinnerware then it is advised that you have sample pieces tested for the various ingredients which might be leaching.

Kilns

Kilns should be checked, so that they meet
regulations stipulated by your regional councils.

Sulpher Dioxide

Sulpher Dioxide
is a strong lung irritant and can form when firing
soluble metal salts.

Lead

Lead is an accumulative poison. It can be stored in the bone structure for years before a fatal dose is accumulated. Beware of raw lead forms, such as white or yellow lead, which are extremely toxic. Use lead frits instead. Do not use for tableware.
For more information on the effects of lead, Please see Article: "Lead"

Gas leak check

To check for gas leaks use a gas detector or
soapy water and a brush, but never use a naked
flame.

Platinum

Platinum may cause asthma.

Carbon Dioxide

Carbon Dioxide
If the oxygen level falls, hearing will decrease, pulse and blood pressure rise. Carbon dioxide forms during combustion firing processes.

Raku OH&S: Using LPG

Raku OH&S: Using LPG
When using liquefied petroleum gas, thoroughly acquaint yourself with the suppliers' recommendations on storage and use.

Alumina dust

Alumina dust is a nuisance to lungs, wear a mask.

Barium Carbonate

Barium Carbonate
A dangerous form of barium, as it forms a soluble
chloride in the stomach and accumulates. It affects
muscles, in particular the heart, increasing its
excitability, leading to high blood pressure and
internal bleeding. Will penetrate the skin. Not
recommended for food ware, as it may leach.

Eating and drinking

Workshop OH&S
Do not smoke, drink or eat in the pottery workshop.

Storing Liquids

Storing Liquids
Do not allow liquid containing ceramic materials (slip, glazes etc.) to dry out. Always keep liquids in containers with tightly fitting lids and dispose of waste, including contaminated packaging in accordance with the suppliers' instructions.

Raku OH&S: If the gas goes out

Raku OH&S: If the gas goes out
Never leave the kiln unattended while firing; If the burner goes out, allow plenty of time for unburnt gas to disperse before re-igniting the burner.

Chromates

Chromates and Chromic Acid
may be cancerous. Will also enter the body through
the skin.
For more information on chrome and its effects, please see Articles: Chromium for Potters!

Borax

Borax
chronic exposure can cause asthma, diarrhea and skin
conditions.

Liquid Petroleum Gas

Liquid Petroleum Gas
can cause headaches, numbness, chills and vomiting,
but is a greater risk as explosive than inhalation.