Clay - COSHH

When working with clay there are a lot of health and safety regulations 

Clay can produce silica dust this dust is hazardous and can cause a serious lung disease called silicosis which can cause permanent disability and early death. This dust is so fine that it is invisible under normal lighting, being so fine this dust can get into the deepest part of your lungs. Thing such as drips and spills that dry are a source of the dust.

Areas should always be washed with damp cloths or mops to avoid the dust lifting up into the air and rooms should always be well ventilated. If your clothes get clay and slip on them and then dry out this can also be a source of dust exposure. So too keep the number of dust sources down don't let clay or slip dry out.

Handling used molds can also create dust, avoid hand sweeping dust or cleaning areas with your hands, use damp cloths to wipe into a bin or clean up. When using tools ensure your tools are clean and don't have old dry clay or slip stuck of them. also keep the work area clear of bags and uneeded items that could cause an accident.

 

-Wet clay is soft and easily workable

-Leatherhard is when the clay is half dried, it is still workable but can support itself.

-Greenware is when clay is in its most fragile state, all the water has gone from the clay at this point, the clay is now ready to fire.

- Bisque clay is clay that has been fired in a kiln, but is still porous enough to absorb water however nothing can be added to at this point and the created piece should be basically finished.

- At this stage you would glaze the clay and then it would go in for another firing in the kiln.

Three main types of firing:

• High Fire - This is mainly for functional pottery, like dishes and bowls, and is fired at approximately 2300 degrees to make the glaze harden to a hard glass coating. The entire heating and cooling process of High Fire takes about 3 days.

• Raku - This process is done in a small outdoor kiln, and the pot is heated until it glows red hot (approximately 1800 degrees) and then immediately taken out of the kiln with tongs and either burning horsehair onto it, or placing it into an enclosed area like a garbage can filled with newspaper, pine needles, sawdust, or any other type of combustible material. This process only takes an hour or so, and always comes out different.

• Pit Fire - This process involves digging a hole in the ground, placing your pots in it with wood and sawdust, and lighting it on fire. It takes about 5 or so hours to let the pots get hot enough to turn rock hard. Chemicals can be added to the sawdust to make them turn colors, like Iron Oxide, or Cobalt. These pots always come out different, and sometimes need to be fired a couple of times to achieve the type of coloration you desire.