once fire vs bisque plus final fire for unglazed pieces
Posted 24 February 2013 - 11:14 AM
I don't think I've seen this topic before and had no results on a search. I am making a japanese lantern textured to look like stone. It consists of 5 separate unglazed parts made of standard 112 which will just be set on top of each other for the final piece. I am in a small class at a community art center and there will be only one bisque(cone 04) and one final firing (cone 6). Due to logistics, it looks like I might have to fire some of it in bisque and some of it only once in the final fire. So here are my questions:
1.Might the parts that have been fired differently look different?
2. since there will be no glaze applied, I think the once firing on a glaze schedule will be ok with respect to the impurities burning out, etc. Am I correct?
3. I want a matte finish. The piece will be outside. Should I leave it bare, or find some type of sealant to protect it that won't impart a sheen?
Oops, sorry. I think I should have posted this in the other section.
Posted 24 February 2013 - 01:42 PM
If the lantern sits on the ground, you might have a problem with absorption, especially if the temperatures get to freezing. Freezing/thawing will stress the clay body.
Posted 25 February 2013 - 05:06 AM
I know when I fire, a bisque fire (cone 05) takes 12 hours to fire to a lower temperature, to burn crud out. Glaze fire (cone 5) goes for 8 hours to a higher temp, much steeper cycle. You might have a problem with things blowing up, or you might not.
Whistling Fish Pottery
Posted 25 February 2013 - 01:43 PM
Kiln Repair Tech
Owner, Neil Estrick Gallery, LLC
Posted 27 February 2013 - 08:01 PM
Sorry I did not make that clear. All pieces were meant to be bisque fired first, then high fired. I think I will try harder to get the 2 pieces I have at home to the studio so they can get in with the bisque fire too. (It's a long drive). I would hate for them to blow up as they were a lot of work...not to mention ruining other students' work. Or I could try harder and work faster to get my own kiln up and running!
Thank you all for your thoughts and taking the time to write.
Posted 28 February 2013 - 07:39 PM
the main problem i see with your original post is the fact that your studio bisques and you're planning to put greenware inside a glaze firing. you need to make sure whomever's firing that kiln KNOWS and adjusts the schedule accordingly - or you risk blowing up your work.