Tips for Uniform Drying


By Rosemary Schalek

Tips for Drying your Clay Piece

Clay shrinks as it dries. When the clay is dried too quickly, the outside surface of the piece dries faster than the center and more stress builds up.  YOU WANT CLAY TO DRY SLOWLY so this doesn’t occur.  You want UNIFORM drying as much as possible.  Non-uniform drying also occurs when you have uneven clay thicknesses.  Having relatively uniform thickness can be important in minimizing cracks. Always join pieces of clay which are about the same stage of dryness. (Adding a wet handle or spout to a leather-hard pot is asking for trouble.)

The most vulnerable stages for stress buildup and cracking/warping are wet to leather-hard and glaze firing.  Vibrations and jiggling can weaken a fragile piece and cause it to crack.  Therefore, don’t slam clay at your table – you can damage someone else’s piece.  Always use the wedging table, not the work table.

 Use the Damp Room to slowly dry your piece as you work on it, covering it in plastic.  When you are completely finished working on it, you can cover it in plastic to continue slowly drying (or leave the plastic off) and place it on the Drying Rack to completely dry before putting it on the Bisque rack.

Mending Cracks in GREENWARE with Paper-Clay Slip
Sometimes, despite all of the above, cracks do happen!  To mend the crack, use Paper-Clay Slip!  Paper-Clay Slip uses Magic Water (found in the glaze area), tiny pieces of toilet tissue, and wet clay.  To make a small amount of paper-clay slip (about ¼ cup), tear four squares of toilet tissue into very tiny pieces. Add these bits of torn tissue to about ¼ cup Magic Water and let soak well, preferably overnight, so that the tissue absorbs the Magic Water.  Once the tissue has absorbed the Magic Water, add a small amount of the same clay as your piece was made from, and mix together to make a thick paste. Always make the paper-clay slip using a 50:50 ratio of paper/water to clay.  Use a brush to wet both sides of the crack. Also using a brush, gently apply the paper-clay slip to the crack, and let SLOWLY dry.

 If a piece has broken off from your greenware piece, it can usually be reattached by wetting both surfaces, applying paper-clay slip and putting the pieces together with a bit of pressure.

When the paper-clay slip has dried, you can use a small piece of fine netting to gently sand the area where you added the paper-clay slip.  You can tightly wrap the paper-clay slip to reuse in the future.

Thanks to Jackie Thompson for contributing to this article.  Portions of the article were found in a previous P & S Newsletter.