Jump to content
Sign in to follow this  
deHues

Dangerous Gasses From Kiln

Recommended Posts

I am firing a bisque in a new L&L kiln with a Vent-sure running. I can at certain times (not exactly sure what temperatures) smell some strong smells that keep me out of the studio. At what specific temperatures are the gasses from a kiln toxic? I have the studio doors and windows open, but I am still concerned. 

Share this post


Link to post
Share on other sites

If you use wax resist, that burns off at a low temp. Also, sulphur dioxide comes off the clay as it is being bisqued. This is why we vent in the first place. I don't stay in my studio when the kiln is firing. Too hot!

TJR.

Share this post


Link to post
Share on other sites

Actually I did do the first firing a couple of weeks ago, with an empty kiln to burn off the elements. Also not using wax resist. Does the sulphur dioxide come off all through the firing or only at specific temperatures. 

Share this post


Link to post
Share on other sites

I usually start to smell wax burning off at around 500F degrees. If you're getting odors after that you may need to adjust the slider on the vent collection box under the kiln. Usually it works well at halfway open.  If you're already there, close it only 1/16" at a time to find the sweet spot.

 

Was the bottom of the kiln drilled for the vent? There should be 2-3 small holes in the floor in the middle.

 

Sometimes on smaller kilns they fit together a lot tighter than the bigger kilns and it's necessary to put a hole or two in the lid to improve air flow. But on your 28" wide kiln I wouldn't expect that to be an issue.

Share this post


Link to post
Share on other sites

Here is clip from an old Clayart discussion, from Vince Pitelka:

 

"The outgassing of toxic volatiles can continue throughout the firing, so ventilation should continue as long as the kiln is firing. At low temperatures you have sulfur dioxide, and at higher temperatures you have zinc and possibly fluorine, lead (if any was present), and other materials. Once the kiln has shut off there is no toxic danger at all."

 

I usually get the sulfur burn-off around 800 to 1000F, especially for bisque fires. You will also get burn-off during glaze firings all through the firing cycle, wax at lower temps, glaze materials at higher temps. My kiln vents to the outside (it is an L&L), but I'm often not able to work in the studio when it is firing. That is one reason I tend to fire overnight.

Share this post


Link to post
Share on other sites

OK, Neil, thanks. I just opened the vent half way. Didn't know that was there. What is a sweet spot and how will I know it is there?

 

Thanks bciskepottery, I will keep the vent on through the firing for sure. I think it was around 800F that I began to smell it but it is up to 1400F now and there is no smell. I am vented to the outside and also it is way too warm in there to be working. I think I will do a few more firings to get familiar with everything and then I will fire overnight. I did a preheat for 10 hours last night to make sure my kiln shelves were dry.

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
Sign in to follow this  

×