Jump to content


Photo
- - - - -

Cooling Ramps In Tiny Kiln


  • Please log in to reply
5 replies to this topic

#1 SleepingBird

SleepingBird

    Newbie

  • Members
  • Pip
  • 8 posts

Posted 15 August 2013 - 10:01 PM

Hi, I have some questions about cooling ramps. I make low fire pendants and small tiles in an electric test kiln, no vent but I wedge it until 250 degrees and keep the upper peep open throughout the firing and cooldown. When the firing is complete, my kiln normally drops 600 degrees in one hour. I programmed in a cooling ramp of 200 degrees F/hr to 1400 degrees, at which point it shuts off. I saw great improvement in the commercial glazes I’m using, mostly in the satin mattes (less glossy than they were) but also the clear gloss glazes seem to have a better clay/glaze interface.

My questions (all temps in F):

1) Is a 200 degree per hour decrease a normal ramp down speed or could I make it a bit faster/should I make it slower? What is an average cooling rate on larger electric kilns? I have Richard Zakin’s Electric Kiln Book, it says a 100 degree drop per hour is conservative, 200 is too quick for most wares. My kiln would have to work really hard to maintain a 100 per hour drop, even 200 is a bit of a struggle for it.

2) Would it benefit the glazes even more if instead of shutting off at 1400 to ramp down to below 1200 degrees, which I’ve read is when the glazes are no longer liquid state? (There was a lot of popping when the kiln shut off at 1400; six minutes later the kiln temp had dropped 100 degrees--but the glazes looked much better than they had without the ramping down).

3) Should I put the upper peep in when the firing is complete to try and contain some of the heat, or will this hurt the glazes by trapping any last escaping gasses within the firing chamber? I have put the peep in at the end before, but didn’t see much of a reduction in the temp drop.

Thanks so much for any help with this, I’ve looked around but there isn’t much info out there; I suppose cooling is probably not much of an issue with larger kilns.
 



#2 OffCenter

OffCenter

    Advanced Member

  • Members
  • PipPipPip
  • 1,372 posts

Posted 16 August 2013 - 08:00 AM

You'll probably get some good answers to your questions here, but even the best of them will not be as good as the answers you could get by using your test kiln to test. As for the Peep in or out, you're just wasting time and elect by leaving the lid open and the peep out.

 

Jim


E pur si muove.

"But it does move," said Galileo under his breath.

#3 SleepingBird

SleepingBird

    Newbie

  • Members
  • Pip
  • 8 posts

Posted 16 August 2013 - 08:16 AM

I've read a lot of differing info on the wedged lid/peep out thing so decided to play it safe. Seeing that a firing in this kiln costs under a buck, it probably doesn't waste more than 10 cents worth of electricity.

Guess I'll do another test load, and look for the answer myself as to when the ramp should end. thanks anyways.



#4 neilestrick

neilestrick

    Neil Estrick

  • Members
  • PipPipPip
  • 2,497 posts
  • LocationGrayslake, IL

Posted 16 August 2013 - 08:20 AM

Keep the peep out during the entire firing. No need to prop the lid. In fact that's making the kiln work harder to heat up according to its program. No problem putting the peep in at the end of the firing, it'll help hold some heat. I don't think you'll need to control the cooling lower than 1400F. You're not going to get any real crystal growth or benefit going lower than that. If you're happy with the results you're getting, go with it! No harm in testing different programs, though. I cool at 175/hr and love the results.


Neil Estrick
Kiln Repair Tech
L&L Distributor
Owner, Neil Estrick Gallery, LLC
www.neilestrickgallery.com

neil@neilestrickgallery.com

#5 OffCenter

OffCenter

    Advanced Member

  • Members
  • PipPipPip
  • 1,372 posts

Posted 16 August 2013 - 09:45 AM

I've read a lot of differing info on the wedged lid/peep out thing so decided to play it safe.

 

Leaving the lid open is not even necessary for a bisque firing where water and organics burn out, but it is definitely not necessary for a glaze firing. Leaving a peep out in a glaze firing is supposed to let gasses in the glazes escape and extend the life of the elements. If it does any good at all, which I doubt, it would be very minor and probably cancelled out by the very minor extra work the elements have to do. I've never fired with a peep out and I even sometimes fire saggers full of coffee and sawdust and my elements last longer than they are supposed to.

 

Jim


E pur si muove.

"But it does move," said Galileo under his breath.

#6 SleepingBird

SleepingBird

    Newbie

  • Members
  • Pip
  • 8 posts

Posted 16 August 2013 - 06:12 PM

That makes a lot of sense guys, I'll nix the wedge next time.






0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users