Under fire Bisque

[Farideh]

Hello,

I placed small plates on very top shelf (top most kiln elements is below the shelf) and the  Orton  cone 04 has barely bent.  Kiln run was set at slow and total run time was about 15 hrs.   I did not have witness cones on other shelves.  I am wondering if I need to change all elements or is underfiring is due to shelf placement above the last kiln element position.  I appreciate your inputs.  Also should I restack and rerun all wear in the kiln.

thanks,

Farideh

[liambesaw]

My top shelf underfired by half a cone sometimes, sounds like you have a similar issue.  They're probably at cone 05 if the cone is bent a little.  Use cone packs to verify.  Should be fine to glaze

[neilestrick]

15 hours is a long firing. What was your firing schedule? Check the resistance of your elements to verify if they need replacement.

When you put cones in the kiln, put them in 3 places- bottom, middle, top, so you can get a better idea of what happened. If the bisque is a little low, it probably won't hurt anything unless it's a dark stoneware that needs the full heat to get everything burned out completely.

[Min]

Going forward, try have an element between each row of shelves, especially for a glaze fire. (some kilns, like ConeArt, can have an area in the middle of the kiln without elements but if there is a thermocouple there then you might not need to have an element between shelves in that area)

[Denice]

I would be looking at replacing the elements,  15 hours is a long time for such a low firing.    If you have to hire someone to do it for you they might have a waiting list.   I  have had to wait 6 months on a rewiring one time,  I finally got my husband to give it a try several years ago.    I am comfortable working on plumbing but not wiring,  I was nearly electrocuted when I was a child.  I have the knowledge to rewire the kiln but can't bring myself to do it.    Denice