Jump to content
elisesurma

Firing Bisque in Computerized Kiln

Recommended Posts

Anyone have advice on if it's necessary to go slow speed when bisque firing to cone 05 and all pieces are bone dry? Also, is it a good idea to do a short hold at the top? And then for glaze firing is it best to go slow speed as well? Thanks for the advice!

Share this post


Link to post
Share on other sites

Use one of the pre-programmed schedules in your controller. For most pots, medium speed is fine. No need for a hold at the top. For glaze firings you can go a bit faster. What type of kiln do you have? If it's got slow-med-fast options on the controller like a Skutt, just do everything on medium. If it's got slow and fast bisque or glaze like on an L&L, do fast bisque and slow glaze.

Share this post


Link to post
Share on other sites

Neil, normally I would NEVER question you because you’re awesome, but I wanted to make sure you said that correctly. I have always been told that bisque should be slow, even if pots are bone dry, and also a one hour preheat is best practice. I exploded some bone dry pots when I didn’t do a preheat once. I also fire at medium speed for my glaze firings. So for me, it’s slow bisque and medium glaze. Sorry, just wanted to make sure!!  

Share this post


Link to post
Share on other sites
22 minutes ago, PotterPutter said:

Neil, normally I would NEVER question you because you’re awesome, but I wanted to make sure you said that correctly. I have always been told that bisque should be slow, even if pots are bone dry, and also a one hour preheat is best practice. I exploded some bone dry pots when I didn’t do a preheat once. I also fire at medium speed for my glaze firings. So for me, it’s slow bisque and medium glaze. Sorry, just wanted to make sure!!  

If your pots are of appropriate thickness, like 1/4" or less, and bone dry, there is no need to do a preheat or fire on slow. If your pots blew up because you didn't do a preheat, then they were either too thick for that speed or weren't actually dry. It can be difficult to tell if things are totally dry, though, so by all means do a preheat if you're not sure.

I work in porcelain, which dries quickly, and doesn't have so much stuff to burn out as stoneware clays, so I often do a 30 minute preheat to make sure everything is totally dry, then do a 5 hour firing. Do what you know your pots can handle, but chances are they can go faster than you think in most cases. Also make sure you're loading them upside down whenever possible, as they'll heat more evenly that way.

And thank you for the kind words.:)

Share this post


Link to post
Share on other sites

 I've been firing everything in my Skutt 818 on med speed (cause the manual says to)  -other than one slow firing because I had a big thick bowl I was worried about. So far it seems to be spot on. 

Share this post


Link to post
Share on other sites

Hi Elise, welcome to the forum.

I would just add that on glaze firings we experimented a lot and found that for our cone 6 firings we go to cone 5 with a 20 minute hold at the end. This hold serves as a cone in heat work and is meant to soak and level out the glaze. By doing this we found we have less glaze defects. I've heard anywhere from 20-40 minutes cited for a cone in heat work and with the 20 minutes we get a half bend on a cone 6 cone.

Good luck, enjoy! 

Share this post


Link to post
Share on other sites

@elisesurma, what type of clay are you using? For white or light coloured clays then what has already been suggested will work but if by chance you are using a really dark or blackish clay then a slower bisque and a hold during the bisque might be necessary. Also, with those type clays going a little under cone 6 is sometimes necessary. Agree with Stephen, just have to run some pots/glaze tests through the kiln and go from there.

Share this post


Link to post
Share on other sites

I will be doing a cone 6 firing tonight but I'm going to try the advice of going to cone 5 with a hold. I have witness cones so we will see. 

Fired bisque with medium speed last night so I will see in a couple hours if anything blew. Thank you everyone for your advice. 

@Min I use porcelain and Georgies dark chocolate clay...so definitely a mix.  

Share this post


Link to post
Share on other sites
1 hour ago, elisesurma said:

I use porcelain and Georgies dark chocolate clay...so definitely a mix.

Have you fired the Georgies Dark Chocolate to ^6 before? No problems? Also, the umber is adding manganese to the clay so the fumes from the kiln need to be well vented.  Curt wrote a really good post on bisque firing dark claybodies at the bottom of this page. From Georgies website re glaze firing this clay to cone 5:

Trail Mix Dark Chocolate (CC535D)

Dark rich brown, almost black. Best when fired to cone 5. The umber addition brings extra flux to the clay, making this a very tight body.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×

Important Information

By using this site, you agree to our Terms of Use.