I am having an issue with standard 112 brownspec. I have been using the clay for about a month now and I have fired 3 kiln loads, each time changing my firing process by 1 or 2 steps. So far I have been unable to solve the pinholing problem in this clay body.
Firing 1. Bisque to ^06 / Glaze to ^6, top peephole out till 1500F then plugged in both bisque and glaze firing. - Had several pinholes on the 112 body, but none in the bmix body.
Firing 2. Bisque to ^05 / Glaze to ^6 (held 5 minutes), top peephole out till 1800 then plugged in both bisque and glaze firing. - Had same pinholing on the 112 body but again none in the bmix body.
Firing 3. Bisque to ^04 / Glaze to ^6 (held 5 minutes), top peephole out the entire time and then plugged after kiln completed. - Still the same pinholing on the 112 but again none in the bmix body.
I love the way 112 looks in the ^6 finished product. I am making some bowls where I only glaze the inside of the bowl and I love the beautiful color and speckles on the outside of the bowl. However I cannot for the life of me get rid of pin holing.
I have read a lot of the threads about pinholing and most people say it has to do with the bisque firing, so some more details about my bisque. I do not stack anything inside of the bisque. I know this is less efficient but I wanted to start out with less and stack more if my first firing came out great. Since it hasn't I haven't increased my load. I use the same exact load in the bisque as I do the glaze firing so plenty of room for gasses to get out.
After bisque cools I take out all the pieces and wipe them with a damp sponge. I let them dry about 1 hour after wiping, then I proceed to brush on glaze while waiting an hour between each coat for the glaze to dry. I wait for the glazes to dry completely about 4-5 hours then I glaze fire.
In my final product it seems most of the pinholing is inside of a speckle. Is this a common place for a manganese speckled clay? Or am I just using glazes that really don't fit my clay body well?
Here are some pictures showing a few of the pinholes, most of them are inside of the speckle:
WP_20140713_002.jpg 44.9KB 5 downloads
WP_20140713_003.jpg 53.76KB 2 downloads
WP_20140713_004.jpg 44.76KB 1 downloads
WP_20140713_005.jpg 51.62KB 1 downloads
I really like the speckled clay a lot, but I am debating on changing to a different clay.
I am thinking about Highwaters Little Loafers or Red Stone. I thought about Red Rock, but it has speckles added so I am not sure if want to go through the same thing.
My plan for this coming up week is to by 25 lbs of Little Loafers, Red Stone, Red Rock, and Brown Stone. Then throw a cylinder, a bowl, and a small plate in each clay and apply the same glaze to each one and then bisque to ^05, glaze to ^6 (5 minute hold).
Does this seem like the thing to do?
I know 112 is a super popular clay, so I can't imagine I am the only person having this problem, yet I can't seem to find other people having issues with 112! Any help or ideas would be appreciated, my kiln is pretty small so I can test stuff very fast. I already have a lot of pieces ready for the next round of testing that are bone dry sitting on the shelves.
Edit: After a much closer look at my first load vs my 3rd the pinholing is definitely less prevalent than in the first firing. So I am on the right path to fixing the solution but I just haven't gotten there yet.