That is really sad to hear! What was the temperature outside? I think I wrote before that my firing was depending on that very much. I could never imagined that for example 20 C difference (in outside temp) makes such a huge difference in firing. For example at summer evening (cca 17C I think) I could not get it over 1000-1100C The problem is that every little thing makes a big difference. I noticed that when something blocked the progress it was time to make changes. I am trying to say that when you saw that you are not getting above 600 C it would be better to stop and not waste any more gas.
as marcia wrote: see if you get a pull of a draft with a lit newspaper torch by your burner port. This is important since you are using a natural draft and no forced air.<br style="color: rgb(28, 40, 55); font-family: arial, verdana, tahoma, sans-serif; font-size: 12.727272033691406px; line-height: 19.09090805053711px; background-color: rgb(250, 251, 252);">
have you tried that?
My kiln is much simpler (and it fired to 1250 C at least 30 times, but it was summer), the air just has to go up and not around... the newspaper torch could tell you if you have enough air. The chimney is not a good idea in my opinion. Before you quit.. maybe try a hole on the upper side of the barrel (in the metal). The thing is small and the temperature will be high enough everywhere.
OH another thing- you might not have enough insulation or the shelf is positioned to low (it could suppress the fire). I am having more room under. Maybe it is just a combination of all those reasons. I would try different solutions: - first the newspaper torch (if that is ok then ...) - firing in a warmer room or a warm day (this will tell you about the insulation) - then the upper hole
I think there is no inkjet that will fire true color (except those with special toners - quite expensive) , cost from 3000 euros (chinese) and cca from 5000 euros (german)
Decal paper + some laser printers (some HP are proven, but maybe there are some others with iron oxide in the toner)- will fire sepia - see my picture
ok here are pictures... measurements: 65x65 cm x 50 cm height + the lid
insulation 16 cm wall, upper hole 10 x 10 cm, the same hole for the burner
It really did quite a good job, I was firing with two shelves and about the same element for measuring temp you have BUT I got tired of sitting by the side every time... and now it is all alone in the garage