Glaze Application and Base Cracking Issues
(Fallbrook, CA, USA)
I recently began using premixed glazes. I fire at cone 5 and was wondering if there is a secret to applying these glazes evenly?
Also, I have had a lay-off in potting and when I started up again, I purchased a white stoneware clay called B-mix. When I have trimmed and allowed my pieces to dry, I am seeing hairline cracks on the bottoms of my pots.
Is this a temperamental clay or can you give me some suggestions. I have been a potter for some twenty-odd years. I love your turquoise cups!
Also, I noticed the rings on the inside bottoms, is that okay? I always try to smooth out my bottoms. I am sorry to burden you with so many questions, but would certainly appreciate your expertise on these matters!
These are great questions, I hope I can answer them for you here.
Regarding glaze application, it partly depends on what the directions for that glaze call for. Some of them are designed for brushing (usually 3 coats), others are for dipping.
I almost always dip my glazes, even if they say to brush them. I'm too impatient for brushing. The key with dipping is to be sure that the thickness of the glaze is just right to get the perfect coating.
You can use a hydrometer to measure the thickness of the glaze. It will help you get it right more consistently. Or you can go by feel, which is what I do, simply by experience and dipping a stirrer in the glaze. But, you run the risk of having one kiln load with a thicker or thinner glaze than the next, if you are inaccurate.
In regards to the cracks in the B-mix that usually stems from one of two things.
The first and less likely issue is that the bottom of the pot needs to be compressed more when you are throwing. Compress it by pressing down with a rib into the bottom of the pot before pulling up. This will help with your ridges as well.
The second and more likely cause of cracking is that you are using too much water when you are throwing and allowing that water to sit in the bottom of the pot too long.
This is usually the cause for me when I have trouble with the base cracking. The reason is that the base soaks up that water and is therefore more wet than the rest of the pot. This causes it to dry at a different rate than the rest of the pot and crack.
Pull the water out more frequently with a sponge, and most importantly, make sure it is good and dry before you finish and set the pot aside to dry completely.
Hope all this helps.
P.S. Those beautiful turquoise pots are by Page Pottery. I love them too. They're available for sale at their website.