meanwhile uptown

that's Kent McLaughlin
he's right up there with Tom and Bob on my list of favorite tinkerers and mad scientists

So we have now had two firings involving vegetable oil. the first was hosted by a 8ish cubic foot reduction kiln, downdraft, with two burners in the back aiming forward, flue inbetween two bag walls.. at cone 08 he replaced one propane with the rotary-style burner and it seemed to be burning all right- smokey, but improving over time. I was in and out of the area- it seemed to be going on a long time, there was plenty of activity and storytelling and at a certain point I saw that he'd gone back to two propane burners. turns out that due to the power of the burner and the tiny kiln, the fuel does not really have enough space to combust properly. not only that, but the cone of the flame exiting the burner is severely disturbed by the narrow channel through which it must pass to get into the kiln. then, once it's in there, it hits a target brick, intended to deflect the flame upward into the chamber, but placed, as it were, eight inches from the wall, fire side. so what happened is that the flame was first compressed, then smacked into a roadblock, and immediately jumped sideways into the pots right next to the flue, and out the flue. the pots in that area were subjected to a sudden and violent temperature increase which sealed the surface and then bubbled it well before normal temperatures.. and that side of the kiln was quite oxidized because the oil had no good way to combust.
round two: I load a soda kiln. crossdraft caternary, about 16 cubic feet. Kent has invented a little fry oil weed burner- 20 dollar propane torch weed burner, two inch cup. he drilled a quarter inch hole for a copper tube to be inserted through the back "wall" of the thing, so that the oil can enter above the propane flame, and burn simultaneously. so at cone 012, I replace one of the propane burners on this kiln with this new tonka burner. I also slide a split soft brick onto the floor of the burner port so that the oil can drip onto this "sponge" and have a wider surface area on which to burn. it burned dirty, belching black smoke. well, Kent's first experience with the fry oil was the same way, and he in love with carbon trap shinos was elated. but when he opened the kiln, pastey white. so somebody out there with a clue- could you weigh in? if there be soot, there be carbon dioxide and monoxide as well, correct? how could he have had a kiln in apparent nasty reduction yet have oxidized results? he was saying that it was in some way related to, essentially the length of the hydrocarbon chain- that with the heavier oil, the oxygen has a hard time breaking into the molecule-- exiting unburned.
the juggle this evening was the standard body reduction one, maintaining heat rise with definitive reduction, now with the extra ball of this wacky burner trying to smoke us out. The idea was to find a place where the oil could gradually phase in, and the propane out. but whenever we tried to make that shift, the smoke was just insane.. so then we tried to spray a little water onto the soft brick sponge as well, to assist in atomizing the oil- but whenever we did that, it was just so much hydrogen reduction too that the temperature would plummet. it was too much water- if we had a little valve by which to control it quite accurately, perhaps. But at that point, I would vote for doing the stair-step burner with the softbrick sponge.
so we dinked around with that for a good few hours, and then I made the call to get on with it, switched back to propane, and put the turbo on. within a few hours the bottom of the kiln was way hotter than the top, and now I've throttled way back to allow it to even out the top. to be precise, it is 4:43, I have my computer sitting on the damper of some other kiln and I'm listening to Aphex Twin. it's pleasant, actually. nobody around. kiln doing what I want it to do, albeit very very slowly. but writing takes time. at 5 am, my friend has a blow slot in the glass shop, and I'm going to go up there to see what he's up to. Once I'm done with the firing.