fusing with ceramic kilns

rosanna gusler · Post by **rosanna gusler** » Sat Oct 11, 2003 7:50 pm

all that mass (kiln brick shelves posts glass) is full of heat energy. when the kiln shuts off the elements for the cool down, the temp will rise a little and then start to drop. if you vent, the thermo couple will read the temp of the fresh cool air that comes into the kiln and mixes with the hot air. then when you shut the lid all that heat stored in the mass radiates back out and the temp will climb again but will stop again lower than it was before. any how the kiln will not cool faster than it can loose its heat. the controller will just wait untill the next set temp is reached and then do whatever you told it to do. it is really better to figure out how to get what you want without alot of flash venting. rosanna

cherylka · Post by **cherylka** » Tue Oct 14, 2003 2:36 pm

Is it a problem if the temp rises higher than the soak temp? If so, should I program to a lower temp expecting it to pass the temp before starting to drop?

Thanks,
c

Lisa W. · Post by **Lisa W.** » Tue Oct 14, 2003 3:12 pm

Hey,
http://www.ugotglass.com/cone2temp.htm
They have a cone-temp schedual.
Lisa w

cherylka · Post by **cherylka** » Tue Oct 14, 2003 3:15 pm

Thanks,

I have a cone temp chart, but what I am not sure about is how critical that high temp is to the glass.

If I set it to 1465, according to System 96 instructions, and it actually goes up to 1500, will there be a problem with the glass.

If so, maybe I should set my hi temp to 1400 expecting it to continue to rise before it starts to fall.

c

rosanna gusler · Post by **rosanna gusler** » Tue Oct 14, 2003 11:52 pm

the answer to that is 'it depends'. how high the kiln goes after shut off will vary with how much mass you put in there. i only use float type glass so i can not say about the other kinds. sometimes i vent a little to stop process at a certain point. it would matter more with drop rings than with full fuse. i do know that alot of up and down on the cool down between about 1200 and 1400f tends to grow devit in my kiln. rosanna

dan001 · Post by **dan001** » Wed Oct 15, 2003 11:17 am

I build my own Ceramic fiber Blanket kiln with an Omega controller and a type K thermocouple.I use the kiln mainly for painting and I come across the situation where I set my soaking at 1250 for 5 minutes and I constantly see the soaking to fluctuate between 1225 and 1280.

Dont worry about it. The reason that you see your temperature going above the set soaking temperature is that the element heat is being sent to the thermocouple directly and the actual temperature in the kiln is more or less 1250 anyways.

I even tried to put my thermocouple below my shelf with bad result because the temp on the shelf is much higher .My thermocouple is 1cm above the shelf left hand side corner

My results are awsome. I have painted on system 96, Uroboros, Youghi and even Oceania.Those glass are so fragile that if it would make a difference I would had problem.

If you need more precise firing schedule let me know

Dan
L&D Design

cherylka · Post by **cherylka** » Fri Oct 31, 2003 11:18 pm

My second firing is in the my automatic ceramic kiln now.

I am doing a full fuse of several pieces all 1/4" thick, some small, and the largest a 5" diameter circle.

There is only one shelf in the kiln, it is about 4 inches off the bottom, the thermocouple about an inch above the shelf.

The kiln temp reached 1465, and then kept right on going. It reached 1570 before I flashed to start cooling, even though I set the high temp to 1465.

Does anyone who uses an automatic ceramic kiln for glass fusing have any ideas for me?

Thanks,
c

rosanna gusler · Post by **rosanna gusler** » Sat Nov 01, 2003 7:16 am

did you program a hold at top temp? did the kiln elements turn off at the set top temp/hold after hold when they were supposed to? if not , there is a controller problem. if so you just need to learn your kiln so that you can program to take these quirks into consideration. i would set a short program as a test. with some sacrificial glass but with as much furniture as you think you will typically use. up to temp fairly fast. then hold for say 10. then off (assuming your controller will shut off , wait and see). then do not open the kiln. just log the temp profile against time. stop logging when it starts to drop . allow to cool naturally. look at the sacrificial glass on each shelf . log this. now you have a bench mark to adjust from. i log each firing complete with drawings and what was on each shelf. then i n ote how everything came out. that info is invaluable. sorry for the epic. rosanna

cherylka · Post by **cherylka** » Sat Nov 01, 2003 2:05 pm

Rosanna,

It was not an epoch, and thanks. You really made me think. I did set a hold, and it did not happen, and the elements did not shut off. I am going to re-read my kiln manual and do a test run.

Another question, if some of the pieces had rather large bubbles, and some had smaller ones, can I refire them to reduce the appearance of bubbles? If so, should I refire them in a slower firing than the test firing you suggested?

One more for anyone out there with more experience than me (practically everyone)... Some sources I read say it is very important to clean the glass well, others don't mention it at all.

What is your experiece. Do you clean every piece of glass you use, and if so, what did you see that made you take this step.

Thanks for all your help.

Cheryl

cherylka · Post by **cherylka** » Sat Nov 01, 2003 3:48 pm

Well, I took my Skutt manual and reread the part about ramp hold programs. And, it states that if you program a rate of temp increase faster than the kiln can manage, it will automatically switch to a High On position and stay there until turned off.

So, when following the System96 recommended program of 2000 degrees/hour it exceeded the achievable rate of increase and turned on.

So, I will reprogram my ramp hold within the achievable limits of my kiln and try again.

Cheryl

Carol · Post by **Carol** » Sat Nov 01, 2003 3:52 pm

You should be okay with your schedule if you substitute 9999 for 2000. 9999 tells the kiln to go as fast as possible.

Martycom · Post by **Martycom** » Sat Nov 01, 2003 8:09 pm

We have been using a ceramic kiln in my classroom for years. They were the first ones that we had access to until our updated fusing one.
Karen's instruction were excellent.. But I use cone 013 for a full fuse.

I noticed that no one mentioned the cone size. Theres a vast difference between the small and large size cones.... Make sure they are the small ones.

rosanna gusler · Post by **rosanna gusler** » Sun Nov 02, 2003 10:31 am

martycom, she is using a controller, not a kiln sitter. rosanna

Martycom · Post by **Martycom** » Sun Nov 02, 2003 1:02 pm

No, Roseanne, I'm using a cone sitter. This kiln is probably 30 years old.
Because it is so thickly insulated, it reduces beautifully.

It has three dials... I begin the firing by turning one on to the medium position for the first hour. Then put all three on to high. When the cone collapses, I turn it off. This was the only we way we had to fuse in those days......(lots of testing for compatability of glass).

We continue to use it as an additional kiln.... Marty

rosanna gusler · Post by **rosanna gusler** » Sun Nov 02, 2003 1:55 pm

the she i was referring to was cherylka. rosanna

WarmGlass.com

fusing with ceramic kilns

Soaking temp higher than set Point

When all else fails, read the manual