In February I discovered some of my pottery developed crazing – small hairline cracks that appear in the clear glaze giving a crackle effect. This crackle effect was not intentional. Since then, I’ve been reading and contemplating what to do with the seven pieces of pottery that exhibited the crazing.
Last week, I decided to refire those seven pieces. I am happy to report that refiring solved the crazed pottery problem! In the picture below, you can definitely see a difference between the two pots.
The pot on the left is underfired due to a kiln snafu. Underfired pottery is porous and porous pottery tends to absorb moisture causing the clay to expand thus cracking the clear glaze. The pot on the right was fired to temperature (Cone 6) which means the stoneware is no longer porous and the clear glaze is as smooth as glass with no cracks! 🙂
This is good news! I do not have to change my clay or my glazes. I simply need to keep the kiln in tip top working condition for the up coming throwing season!
A note about crazing: Any and all glazes will craze over time. Functional pottery, like my favorite coffee cup pictured below, suffer a lot from heavy use – hot water, cold water, in and out of the microwave and dishwasher. Whether or not you should continue to use pottery that has some crazing is debated among potters. Some claim the tiny cracks weaken pottery. Others say tiny cracks can harbor bacteria. Then there are others who say don’t worry about it. I tend to like the ‘don’t worry about it’ school of thought. 🙂 Simply examine the pottery from time to time and judge for yourself whether or not to continue using the pottery. My favorite coffee mug has been in use for 15 years and still going strong; crazed and all! 🙂