with 1" thick white blanket of what i call Insu-Wool.
>>>>>>>>>>>this is what we call Kaowool. Hope you wore a mask when you built this thing, as those fibers are VERYVERYVERY bad for your lungs.
i am using a regular LP Weed burner inserted just in side the bottom of the kiln. I have approx 2 1/2" x 9" of opening around the burner
>>>>>>>>>>>I think this hole is too big. Your burner should not be inside the kiln; it should be just outside the kiln; maybe 1/2 to 1" away. This will allow for airflow into the kiln.
and a 6' dia hole in the top, in line, directly above where the burner is inserted..
>>>>>>>>>>>Your hole in the top should be about half this size and in the center of the tophat. If it is directly above the burner, your heat is escaping before it has a chance to get inside the kiln.
Just a note, that when the kiln got to apprx 1600 the vent was leaving a hot blue flame out, what i see as wasted heat.
>>>>>>>>>>This is what we call reduction, which does cause temperatures to stall, especially if (frankly - but please don't be offended) you are new to fuel-burning kilns. It means there is an oxygen starved atmosphere inside the kiln. Putting your burner OUTSIDE the kiln as I noted above will help this problem. Leaving your damper open will also help, but as I said before, 6" is too big. For a 27" tophat, the opening should be more like 4".
I will make you a sketch and send to you as a jpg file of how to set your stilts for good flame flow inside the kiln. You also need to be sure your insulating bricks are fitting firmly together and there are no gaps.
where are you located?
Lisa Skeen www.living-tree.net
Living Tree Pottery & Handmade Soaps