Noobie teacher messed up!

[AdrienneD]

Hi everyone, ive been reading on this bulletin and think I know what to do now, but need some extra advice. 

I'm a new middle school art teacher, and not as versed in ceramics as I should be. BUT I love it and  know enough, however the kiln I'm using seems off? I used a sitter bar and cone for my 04 bisque  (earthenware, white).  I was adviced by the previous teacher to run it on high for only 4 hours, and to set the timer to 8 hours. (Low for 2, Medium for 2 and high for 4.) Well the cone never bent, and the sitter never shut it off, and so i kinda panicked because it's our first project, and turned the kiln off!!!!

Did I just destroy all the kids work???? What will happen to the glaze once they apply it,  or how do I know if I should fire again? Also, do I fire at low, med and high ALL again? Help!!!! 

Thank you. Xoxo

[neilestrick]

You got some bad advice. You need to let the kiln run until the sitter shuts it off. The pots will be underfired, but no way to know how much. What model kiln do you have?

[GEP]

Yes, you got some bad advice.

Yes, you can refire this bisque load and it will probably be fine. Bisque firings do not need to be as accurate as glaze firings.

When I fired with a kiln sitter, my bisque program was low for 2 hrs, med for 3 hrs, high for ?? until kiln shuts off. Usually around 9 hours total.  

For your refiring, turn the timer all the way up to 12 or more. You’re not really going to use it this time. Instead, you’re going to hang out with the kiln during the high phase, and note exactly when the bent cone shuts off the kiln. Once you know how long this firing actually takes, you can use the timer as intended from then on, by setting it to about an hour longer than the kiln needs. 

[AdrienneD]

Thank you both for so much for such a fast response! Sooo,  because I'm re-firing, and already went through it all, for this specific fire should I just do low for 1 hour, med for 1 and high until it shuts off.. etc, etc.

Also my kiln is giving off terrible fumes during my medium fire, I had to crack a window but only have bottom ventilation? Is that normal?

Again thank you for helping this newbie out! 

[GEP]

2 minutes ago, AdrienneD said:

I just do low for 1 hour, med for 1 and high until it shuts off.. etc, etc.

The pots would probably be fine if you did, but the reason why you need to repeat the slower schedule is because you need to time exactly how long the firing will take. This way, you’ll know what to expect for future firings. 

Bisques firings do smell a little, and cracking a window is normal. 

[AdrienneD]

Thank you! I guess for some reason I was scared they'd melt if I repeated the whole thing.  lol

 

I really appreciate it! 

[GEP]

31 minutes ago, AdrienneD said:

I was scared they'd melt if I repeated the whole thing. 

Nah, nothing like that will happen in those low temperature phases. Fire away!

[AdrienneD]

Do i new to let the bisque cool completely before firing again? I just got here and its still pretty hot, some warm. 

[GEP]

It wouldn’t hurt the pots if you started now. But again, you’re trying to figure out the timing of a normal firing, so wait until the kiln is back at room temp and start from there. 

[Stephen]

2 hours ago, AdrienneD said:

Do i new to let the bisque cool completely before firing again? I just got here and its still pretty hot, some warm. 

adding to GEPs advice to zero in on your firing time, I would also start a kiln log book and record every firing and keep track of how long to shutoff so as it starts taking longer to get to temp you can evaluate when its time to change the elements. I don't know your kiln but I think the consensus is that you can get about 100-125 combined firings (bisque and glaze) from a set of elements on most models. More bisque and less glaze so really the number glaze firings determine the limit if you use the same kiln for both.  If you post the model for Neil he can probably give a better guidance on the actual number you can expect. If you can figure out last time elements were changed and start your log with that number then at least you will know when you are in the range so if the firing become both really long and/or the kiln still does not reach temp then you know the possible solution, it's normal maintenance so be prepared and maybe even get it in the budget as soon as you can so a set of elements is on hand when the time comes so the class will not be dead in the water while you try to get a several hundred dollar plus purchase approved. Other things can cause a kiln not to reach temp but if its due for a set of elements anyway then that's a great place to start and good time to do it.

The timer is a safety precaution so if the cone in the sitter never falls or the sitter bar malfunctions the kiln will not just keep going indefinitely and  both ruin the pottery being fired and become a hazard so I would put it at least out a bit so that it does not start turning your kiln off as the elements age and firings take longer. I know some people don't do it on every firing but I always place a cone pack with a cone one below, the target one and one above (5,6 and 7 for a cone 6 glaze firing) on every shelf  so I know exactly how hot it fired. 

Good luck with the class!