Special instructions on drying Core Cork Clay

The following information was provided by ACS after we had continuous problems with fine work cracking during firing. Note that it has not been edited by us :D!

Tip 1:

Drying completely at room temperature is recommended. Yes, cork clay dries very slowly, and it is better to consider having some stock of dried core cork with your desired shapes prepared well in advance, i.e. several weeks.

Possible reasons for cracks on surface, deforming or swelling up can be caused when the cork clay was formed without applying enough pressure to make a shape. When the shape is rough and has a soft core, more air is captured inside. The Air will expand during heating and deform the created shape. Make sure to apply enough pressure to create a dense core without any trapped air.

 Tip 2:

 If you want to dry it faster please try the following steps.

1. Drying at room temperature is recommended (Of course, better to place it in any warm dry room than humid place). Consider also the current weather conditions, which may influence the drying time.

2. When you can feel that the surface of cork clay is quite hard, try to place it on top of the kiln at 800 deg. C. for a while or apply a hot air hair dryer with low power for a while. It should take at least 20 minutes and up to several hours depending on the volume and shape of core cork clay. If you have a kiln, you could consider using the remaining heat of the turned off kiln in between tasks.

3. To check the moisture inside of cork clay is same as when you check if Art Clay Silver piece dried or not. Take warmed up core and place it on the handy mirror or clear stainless steel plate. If there is no steam (condensation) visible on the mirror then it should be dried out.

 Following is reference instruction extracted from Project 4 of Art Clay course.

Making core materials.

> When making  core materials with cork clay for earrings, the core size should be about 2cm in diameter. When they dry, they will shrink about 20% and become about 1.5 cm in diameter, which is appropriate size for the earrings.

>Make a ball-shaped core with the cork clay, and put a toothpick into it. If a minor crack appears on the surface, moisten the area and use your finger tip to smooth. For a larger crack, moisten the area and add some cork clay into the crack, and then smear. Make a smooth suface as much as possible.

>Cork clay has a tendency to expand or change its chape under rapid temperature change. Dry completely at room temperature is recommended.

>To make a smooth surface, you cna use a file and sandpaper after complete drying.

October 12, 2006