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tstst

Slow bisque kiln help

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Hi, I'm quite a rookie at this so please correct me if my terminology is wrong . I am trying to find a solution for bloating & pinholes that I experience in my clay body (KGM by Valentine Clays) and I read that perhaps it could be due to the bisque firing.

I was looking up some recommended schedules online and they have a few "holds" after the ramps. My kiln only has 4  inputs, so I have to choose which of these 4 to be set as ramps/ holds.  It seems quite limiting and I would like any advice I can get to find a slow bisque schedule that would work for me. At this point, I'm just doing test fires to find out why my clay body is doing this.

 

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Hi Tstst!

Regular contributor Glazenerd has posted bisque schedules here, with some details on why the holds ...looking...

Overview

Some specific defects; see "Cone 6-10 Firing Schedule for dark or red bodied clay bodies."  in last post

See also

 

Perhaps someone familiar with your clay can add more - hope the above links are a good start? There are several others threads on the subject here as well.

My kiln is fully manual, so I'm watching for the critical ranges and fiddling the switches to get the slow down (holds)...

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8 hours ago, tstst said:

I am trying to find a solution for bloating & pinholes that I experience in my clay body (KGM by Valentine Clays) and I read that perhaps it could be due to the bisque firing.

Could you post your firing schedule that you've used so far for both bisque and glaze firing? Also a picture of the pinholes and bloats. I looked up the clay you are using and it's described as a smooth off-white stoneware that goes to 1250C so my first thought wouldn't be the bisque firing that might be the problem.

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5 hours ago, tstst said:

Thank you Hulk for compiling all the links! The critical temperatures one is going to be really helpful. I will pore over these links for sure.

Time at top temperature is very key else everything is rate based. Typical slow bisque cycle 14 hours. This is all assuming you are bisqueing  to cone 04 and  glaze firing to 6 or 10. Just checking, how long are your bisque firings now? Most manufactures will provide direction when a clay body is a bit tricky, they don’t want a bunch of bloating complaints. Many of the suggested schedules will come with a hold at or near top bisque temperature. Again in general time at top temperature becomes important to completely burn everything out, the rest of the schedule is mostly rate based to allow things to happen gradually as the clay changes.

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@tstst Bloating and pinholing are two different things. Bloating is when the clay has bubbles in it due to off-gassing, usually from over firing. Pinholing is a glaze issue. Give us more details about the problems, plus your firing schedules and temps.

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