First glaze tests down the drain

[yappystudent]

For some reason, probably because I didn't listen to Neilestrick's advice about not cracking the lid of my new Skutt, the kiln overfired and only a few of the glazes I tested for ^6 looked like they weren't ruined, basically the ones I've already had experience with being very stable. I was trying to preserve a lot of colorful glazes and it seemed logical to let more gases escape at first, it didn't seem terribly important at the time; but the manual seems to say ??? this might have caused the ^6 program to overheat the kiln. At any rate, back to the lab again. At least that little dish kept the end of the ^5 test from touching the shelf. 

For the record mainly what happened was my ordinarily colorful glazes were washed out and some colorless, some shimmer glazes had their 'glitter' melted into little black runny spots. My red cone 6 clay tests slumped a little. As you can see ^5, 6, 7, cones all melted. I'm guessing it got to cone 8-10?

Here's a photo of the kiln tests for that firing, which was set to the cone 6 program on the control box, following the manual. I'd probably keep this disaster to myself except that I've just started using a kiln of my own and maybe someone else has some ideas why this happened other than don't crack the lid next time? 

 

[Mark C.]

The cone 7 does not look all that overfired. When the tip is equal to the base it end point-its somewhere in the cone 8 range is my guess.I'm not used to the pre made cone pack base.

Nice art though.

[JohnnyK]

Hey, Yappy,

Learning the operation of the controller on a new kiln can be a trying experience. When I first started using my new Orton controller, I found that I was over firing by about 1 1/2 cones. What I wound up doing was changing the temp offset by +45 degrees. When the ambient temp is 65* the controller is telling me it is 110*. Since making that initial change, and also making adjustments to the soak time at the end of the user defined program, all my firings have been right on. I think it took me 4 or 5 firings to get things the way I felt they should work. BTW, I'm using some of John Britt's user defined firing programs with some slight modifications to compensate for the way my Cress Kiln fires.  Hope this helps!

JohnnyK 

[yappystudent]

TY JohnnyK, at least I'm not the only one. Also forgot to mention I put in a hold time at the end for 25 min because it seemed like the thing to do. I guess I'll try cone 5 next time and no hold, I think. 

[neilestrick]

Cracking the lid did not affect the high end of the firing. The hold time is what did it. A 25 minute hold will get you at least one more cone in heat work. You may also need to calibrate your thermocouple, or just fire to a lower cone to compensate.

[Min]

Yappy, if you put cone packs inline with the spyholes you can monitor the cones towards the end of the firing.  Wear glasses meant to be used for looking into a kiln to protect your eyes from both UV and IR radiation, they will be green #3 lenses. Shut it down before it overfires and do the tc or cone offset if necessary.

[yappystudent]

TY for the info. 

[oldlady]

yappy, if the Cone Box Show still exists, i think you might have a winning sculpture!

[yappystudent]

One last note: I decided to save all the tests because I might as well know for future reference what my glazes look like when over-fired, as well as the few glazes which actually looked pretty good in spite of it. This involved picking some out of the trash. No satisfaction allowed when progress must be made. 

@Min, I wonder if my glasses for viewing the eclipse last year would work. (It was spectacular and I'm sure I saved them somewhere.)