Drying pottery and clay objects is an important step in getting them ready to beired. There are two overarching considerations
- Clay objects, especially those with protuberances or uneven thickness (e.g. handles) need to be dried evenly.
- All clay should be bone dry before being loaded into the kiln for bisquing.
- Place pots on shelves so that air can freely circulate around each piece.
- Do not force dry pottery. Using heaters or hot air blowers like hair dryers can cause severe cracking, especially when the clay is already leather-hard or drier.
- Slow, even drying is best. If pieces are drying too quickly, cover them loosely with plastic. If there is high humidity, cover the piece with newspaper, then plastic. The newspaper will absorb any condensation.
- Do not attempt to dry an object beyond leather-hard without removing any inflexible armatures. An armature that cannot be compressed easily enough will cause the clay to crack.
Use Wire Racks to Dry Clay Slabs and Tiles
Slabs and tiles are especially prone to warping and cracking because they usually have only one long surface exposed to the air, causing the slab to dry unevenly.
One method to enable a slab or tile to dry evenly is to place it on a wire rack after it has been formed.
- Roll out a slab onto a piece of fabric.
- Lift it, in sling-like fashion, and move it to a rack.
Doing it this way helps decrease the possibility of the clay being folded or severely bent which causes internal stress that can also lead to warping.
Use Drywall to Dry Clay Slabs and Tiles
Since drywall is made of plaster, it can be useful when working with slabs and tiles. Just like plaster, drywall will absorb moisture from the clay. Be sure to get regular drywall, not the types that have moisture barriers to reduce mold.
- Roll slabs or tiles on sheets of newspaper.
- Once rolled, transfer the slab or tiles to the first piece of drywall.
- Cover with another sheet of newspaper, then place the second piece of drywall on top.
- Repeat as needed.
- Allow the slabs or tiles to remain sandwiched in the pieces of drywall until stiff leather-hard or bone dry.
The drywall will absorb moisture from the slabs and tiles from both sides, allowing the clay to dry evenly and slowly.
Important: Any speck of plaster dust or particles that get into your clay can cause it to explode in the kiln. Be sure to have sealed any cut or open edges of the pieces of drywall. Use three strips of duct tape per edge; one centered down the edge and one overlapping the first strip of tape on either side of the sheet of drywall.
Dry Clay Lids and Jars Together
Whenever you have a lidded form, whether it is hand-built or thrown, you need to join the lid and jar together as soon as they are dry enough to retain their shape under the weight. This will help ensure that the lid and jar will continue to match one another. Otherwise, warping while drying or in the kiln can make a lid unable to fit in its jar.
While the clay is at all damp, you cannot place the lid directly on it or the clay may weld itself to the jar's clay. Therefore, tear pieces of paper towel and lay across the area where lid and jar meet.
How to Dry Large Pots and Clay Objects in Progress
When working on a large project, you often encounter the problem of needing the bottom of a pot or clay object to stiffen enough to take the weight as you continue to build the upper areas. To do this, a few options are depending upon how soon you will be back to work on the piece.
- If you're standing by the work the whole time: Cover the upper edges with folded damp paper towels and leave the rest of the piece uncovered. When the paper towels are fairly dry, check to see if the bottom area is stiff enough for you to continue.
- If you're going to be done for a little bit: Cover the piece loosely with plastic, allowing the bottom area to be exposed to the air. Check on the piece's stiffness every hour or so.
- If you'll be back tomorrow: Cover the upper edges with folded, very damp paper towels, then cover the entire piece loosely with plastic.