Kiln Firing Discussion

Discussion on kiln firing

This is a transcription of a discussion between leebc and his friend spoony about how she fires her kiln. It is edited for content.

Intent is to create a write-up that presents the information in a more linear format.

Thursday, May 12, 2022

leebc — Today at 9:40 AM
How do you feel about "firing a kiln unattended"?  How much do you "attend" your kiln?  What do professionals say?

spoony — Today at 9:44 AM
I generally just make sure not to fire it if no one is going to be home in the 8 hours it’s firing

leebc — Today at 9:50 AM
hummmm...  And if someone is home?  Do they check it periodically?  Or just listen for the fire alarm? 

spoony — Today at 9:51 AM
At school someone would just come check periodically through the weekend (their firing cycles were generally like 48 hours)
Listen for the fire alarm
I do check it now and then but mostly to make sure it’s heating/cooling as needed
(Yesterday that paid off cause it turned out I forgot to set the timer to the max time allowed before shutdown, so it shut down 3/4ths through heating - which is just one of the fail-safes)


leebc — Today at 9:58 AM
What were you firing to?   The slip-mold-clay Ryan is working with wants Cone6

spoony — Today at 10:02 AM
Build -> fire to 04 -> glaze -> fire to 6
Or whatever the glaze requires (4-6 for cone 6 clay)

spoony — Today at 10:07 AM
I would start with a low fire clay. Still same process but the glaze fire is 05-06 rather than 4-6
I would also check to make sure the slip cast clay is actually 6 not 06

leebc — Today at 10:08 AM
Well, he's already made several of these slip castings and wants to fire them.   I'll encourage him to fire some low temp stuff first.

spoony — Today at 10:08 AM
Have him send a link to the exact clay?

leebc — Today at 10:10 AM
https://highwaterclays.com/products/cone-6-white-stoneware-casting-slip
Highwater Clays
White Stoneware Casting Slip (Cone 6)
The White Stoneware Casting Slip is a smooth pouring stoneware slip which releases easily.  Excellent for utility ware. Cone 6. At Cone 6:  Shrinkage 13.0%;   Absorption 2.0%. IMPORTANT NOTES: This item cannot be shipped via ground shipping.  It must be picked up in our retail store or shipped freight (freight quantity
White Stoneware Casting Slip (Cone 6)
OH!  it's stoneware. 
tbf, he can probably call them for a walkthrough....

spoony — Today at 10:17 AM
Well firing is circumstantial so whatever you asked before might not match anyway
But yeah he needs to fire his slip casts to 04
Then glaze with a glaze that fires from 4-6
NOT 04-06: 4-6
And the initial fire is 04
No glaze before then
No glaze on the bottom (if he’s dipping, he needs to wax the bottom)
And wipe off the glaze from the wax

leebc — Today at 10:20 AM
Roughly how long should an 04 firing take?    How long should a 6 take?

spoony — Today at 10:20 AM
Depends on the kiln and speed. Mine does 04 at med speed in 6-8 hours
I’ve never fired to 6 - at school we loaded on Friday and unloaded Monday

leebc — Today at 10:21 AM
did they attend it all 48 hours?

spoony — Today at 10:21 AM
Nope - just people would come in over the weekend to check on it
Unless it was a soda fire (you have to manually set the flame)

leebc — Today at 10:22 AM
and that was electric?   or gas/wood?
to 6

spoony — Today at 10:22 AM
Most electric, some wood and gas for soda/salt

leebc — Today at 10:23 AM
main question being: the electric ...may be able to get up to 6? 

spoony — Today at 10:23 AM
Those you have to keep watch on, turn the flame up and down, and at one point open it and throw in salt
What’s the kiln? And what’s it’s sitter?

leebc — Today at 10:25 AM
https://wiki.tampahackerspace.com/Tools:_Jen-Ken_Kiln

spoony — Today at 10:26 AM
Oh good I use a similar sitter
It’s usually got pre-programmed things and should be pretty straight forward. Click button to start, takes you through a menu that you can scroll through options with the up/down arrows, last click is ‘start’
Yeah cone 6 is its max temp looks like
Typically you want your kiln to be rated to fire one cone hotter than you want
Oh though I guess technically it can get to 7 so you’re probably good

leebc — Today at 10:37 AM
ok, cool. or....hot, rather.

spoony — Today at 10:37 AM
Actually teeeechnically it can get to 9 depending on heat speed
Slow has a lower final temp than fast
And it can get just to the final temp of 9 at medium speed
You’re gunna want a peep hole plug

leebc — Today at 10:40 AM
is it missing in the photo?

spoony — Today at 10:40 AM
Yeah

leebc — Today at 10:47 AM
Because someone going to ask, what was "School" for you for this?

spoony — Today at 10:50 AM
Ceramics 1&2 at spc
The click sequence confuses me every time XD
I believe that’s just the external version of the sitter in ths kiln 

<video>

leebc — Today at 10:55 AM
Does the kiln plug into that sitter and it ...does things based on the temperature it reads through the peep?

spoony — Today at 10:55 AM
Yep

It’s not quiiite as accurate as the sitter plugged directly in, but close enough for the temps I work with