How to stack gas kiln properly?

[Bill Kielb]

So here is a thought that may make sense and an idea for evenness.

If your shelf is close to the perforated grill it restricts the gasses from leaving by way of the flue. If your shelf is elevated higher above the perforated floor, not so much restriction so …….. you may be able to control this by closing your damper more than usual. The consistency here is anytime your damper is opened too far your kiln fails to rise or begins to drop. Might be a simple way to control your firings no matter how you need to stack (within reason) to fit your wares. Easy to test out anyway.

Second tool would be slow firing at the end. Slow down to 60c degrees per hour in the last 100c can help things even out.

[Babs]

3 hours ago, Bill Kielb said:

So here is a thought that may make sense and an idea for evenness.

If your shelf is close to the perforated grill it restricts the gasses from leaving by way of the flue. If your shelf is elevated higher above the perforated floor, not so much restriction so …….. you may be able to control this by closing your damper more than usual. The consistency here is anytime your damper is opened too far your kiln fails to rise or begins to drop. Might be a simple way to control your firings no matter how you need to stack (within reason) to fit your wares. Easy to test out anyway.

Second tool would be slow firing at the end. Slow down to 60c degrees per hour in the last 100c can help things even out.

Indeed. I am thinking the perforated floor and space beneath is equivalent of the space below the lowest shelf in most kilns designs. (NO perforated floor).

No bag wall, reopening damper, heat flame sucked across bottom of kiln, temp drop.

One big pot or lots of shelves , no matter,  keep a log, check everything and write up results hourly.

 

[Kelly in AK]

Sounds like you’re dialing it in nicely! I mean going from not getting above c.6 to reaching c.10 in one and a half tries is a leap of progress.  At this stage you may be able to get things working the way you want from finding optimal primary air and damper settings. One step at a time, and keep good records.

For good measure, make sure you give damper adjustments time before you decide what effect they’re having. In my previous kiln opening the damper would even out the temperature, but only after several minutes. I had a pyrometer on top and bottom and could watch. At first the top starts dropping, the bottom stays the same. Then the bottom begins climbing and the top cools more slowly (bottom catching up). Finally, after about 30 minutes, they even out and climb together. 

[Antoinette Brown]

Babs, do you think a flue over the kiln would improve the draft? The lady I bought it from didn't use it at all. I am really puzzled that the temperature rises when I close the flue it should be the other way round! When I open it it drops! And by closing I don't mean a tiny gap I mean at least three quarters. But if I reduce heavily the temperature rises.

Yes, fibre kilns go up fast I remember my very first firing in that port- kiln It was at 600C in half an hour.

There are a couple of things I could try :

• Not staggering the shelves at all
• Using the flue (I would need some heat resistant flashing I don't want the rain on the kiln)
• blocking the gap between the lowest shelf and the floor (grill) 1 inch if it would do something

[Babs]

Damper open creates a draw in from airitakes around burner ports  of cold air ,  so temp will drop??? Yes. Heat will leave kiln esp if the gap under bottom shelf to the flame chamber  exists.