Pottery Student Information
When working on a sculpture or a piece that will take a long time to finish you will need a damp box. To make your damp box: get a large plastic tub with lid from a discount store. These are sold as storage or file boxes. Pour plaster of Paris two to three inches thick in the bottom of the box and allow to dry completely. After the plaster of Paris has cured (about a week) you can use the box. Simply wet the plaster of Paris and place your piece in the box, you can cover with plastic if you like and close the lid tightly. Work can be kept damp in the damp box for months as long as you occasionally wet the plaster of Paris.
If you make a wide flat piece and want to keep it flat during the drying process, fill small bags with sand and place across the inside bottom of your piece. This allows the piece to dry and shrink without bowing in the bottom.
After you have finished a piece, try using a cloth such as a pillow case to cover your piece and allow it to dry slowly. Plastic can cause the “green house effect” where water droplets form on the inside of the plastic and drip down onto your piece possibly causing a stress crack. By using a cloth you allow the piece to dry slowly and evenly without stress and water saturation.
When working with slab construction: be sure to bevel each piece before you put them together and try using “magic water” instead of slip or water to bind the two pieces together.
When you discover a hairline crack around an attachment to a piece such as a handle or knob, you can use vinegar to smooth the crack instead of water. The vinegar allows you to move the clay particles without causing more stress to the place where the two pieces were joined.
You can use wax resist over a shino glaze to slow down the drying of the glaze and resist the effects of carbon trapping. After you glaze your piece in shino, paint your design using wax resist on top of the glaze. The unwaxed area will dry faster bring more soda ash to the surface and carbon trap while the waxed area will stay a bright orange.
When you throw a wide piece on the wheel head and want to lift it off without it warping; Take a piece of newspaper and set on the rim of the pot. Then wait to see the paper saturated showing the rim of the pot. Cut the piece with your wire freeing it from the wheel head. You can then lift the pot off, trapping air, and the piece will not warp.
Avoid stress cracks by drying your pieces evenly. Use an old pillow case or piece of cloth instead of, or in addition to plastic. Plastic can cause water droplets to form on the underside of the plastic, dropping back onto the bottom of your pieces increasing the chance of stress cracks.
After trimming use cloth to dry the pieces slowly, or use a piece of cloth between the pot and the plastic to keep pieces most between work sessions.
When your bag of clay is too stiff and you need to soften it for use; you can freeze your clay, thaw it out and the clay will be softer. You will need wedge the clay very well to make sure you have even moisture distribution. You can also take your bag of clay, open the bag, and use a long dowel or wooden stick to put holes in the block of clay, stopping before you go all the way through. Fill each hole with water and let the block of clay sit for 24 hours or more. Clay will be softened, but will need wedging to ensure even moisture distribution.
Last Updated on Wednesday, 26 September 2012 12:21