So I'm done with the Penland part of this adventure. The Penland part was excellent in any number of ways- I learned a lot, not necessarily about firing with vegatable oil, but more about the puzzle of humanity, the navigation of a class, and the funny ways that my hopeful nature reveals itself... we were a bit of a ship without a rudder. what to do? some sulked on the bow. some threw bread to the seagulls. some cobbled together parts and lashed it to the starboard rail...
I'll try to summarize the information of the second month here: we focussed on the salt kiln, in which we could fire green-glazed work. Kent pulled one of the propane burners out and substituted his weed burner. It worked well enough, lagging in the first part of the firing, and catching up by the end. We maintained, to our ability, a flow of oil along the iron channel, ending at or just before the soft brick "wick" at the end, resting inside the kiln firebox. Readings on the amount of propane consumed in this firing were difficult to make. We did go through five gallons of vegetable oil. That area of the kiln was primarily oxidized, as expected. Nice results. This was the case in two of our salt firings. For the final firing, we had all four burners on propane, for various reasons.
In an experimental mood, I did modify the soda kiln for a firing, about half-way through the course. With the intention of hooking up the big rotary burner, I built an interior firebox that extended the combustion space needed for the fry oil.
photoshop would help- soon everything will be properly oriented..so what you're looking at is that I removed half of the existing bagwall, designed for the short propane flame, and built this perforated wall to the side, and a solid wall in the back. then fellow student Joshua and I tried to imagine how the flame would move through there- it goes along, it hits a big blockade. it bounces mostly upward. it hits another blockage- the shelf above it. at this level, the wall is more open, so the hope of the configuration was so force the flame sideways and upward among the staggered shelving of the next level. and in the reading of the cones during the firing, it seemed like it was pretty much working- at first, the top back was hottest, as the flame was simply rising , and the portion next to the door, which was stacked as normal with pots, was fairly even at red heat.. we switched to fry oil. cones fell faster than I've ever seen cones fall before- all over the kiln. I was trying to maintain a good body reduction, but the final results showed a general lack of success., or perhaps having lost it later in the firing..
I kept the propane burner on as well, so that there was one big fry oiler, and one propane as per normal procedure.. I tried turning off the latter at some point, but had no temperature increase with the oil alone.. probably just too crazy of a flame path for it to do it's work properly. what was perplexing to me was that at a certain point, about cone 9, nothing i did could increase the temp. I tried everything i could think of including firing neutral, to no avail. results showed up oxidized, with the hottest part of the kiln at the middle of the door, right where the flame would have been most violently redirected. variation from cone 8 at the top back (above the interior firebox contraption), to cone 11 at the middle and bottom door.
For a few reasons, that was the last experiment. I can't blame the other students for not wanting to make pots that were simply doomed to one poor firing after another. High-risk firings need prior parental consent. What did we learn? well, ironically, one thing we learned is that maybe the soda firing was not so great, but the salt firing wasn't perfect either. they occurred simultaneously, and fell at opposite extremes of the oxidation/ reduction. The salt firing after that wasn't perfect either, underfired. the last one was pretty good overall- these things take time! what did we learn? that the nature of the beast is tempermental. build your own kiln, expect quite a few highly imperfect firings. in the meantime, quit whining.
I will keep you posted with oily firing progress in my round kiln in portlandtown.
the next few posts will be about the other clay class, and my subsequent travels. be sure to check out Rob's blog- potteryodyssey. cheers from DC! ( I touched a 4000 year old pot today...)
