Sunday, January 07, 2007

So...... How Was Your Day?

I awoke early this morning, to run errands. I've been working a lot of overtime at work, with a new assignment, so haven't had time for much of anything. I had to fill a propane tank, drop a couple of books off at the library, pick up some empty paint cans, and also stopped by Target for some sundries.

The plan was to re-fire a few of our pieces that we were not satisfied with, and to fire the one rocket that I have made in the last month or so. Julie had one of her vases with a dragon emerging from it, and I had several of my rockets. Some of the pieces we added more glaze to; primarily Seth's Luster, but also there was a dark patch on the body of one of my rockets that needed to be coated with two layers of white underglaze and a thin layer of clear crackle. We sat around the kitchen table, brushing on extra layers of glaze. Raku ware is non-vitreous, so the pieces were still able to absorb the water from the glaze, which is what helps bind the glaze to the piece. We got together enough pieces to do two firings, with each of us pulling two pieces from the kiln.

When I unwrapped the kiln, the base seemed really damp. Julie and I pulled out the burner, reduction chambers, tongs and gloves from the garage. I also turned on the water to the hose bib for the back of the house. It usually freezes by this time of year in New Jersey, so the hose bibs need to be turned off and drained to keep the pipes from cracking.

After attaching the burner to the newly filled tank, we loaded the first four pieces into the kiln (two refired rockets, one refired dragon, one new rocket), and lit things up.

Billows of steam rose from the kiln. At first, it rose from the central vent hole in the lid of the kiln. The pyrometer showed that the temperature rose to four hundred and fifty degrees, then stopped. There was so much energy being used to convert the water trapped in the soft brick of the kiln to steam that we couldn't get the temperature to go up. I finally throttled the kiln back to about quarter power, and decided to wait things out.

Steam started to come out of every opening of the kiln. There are cracks between kiln bricks, narrow holes that once carried power to the kiln elements, and gaps around four peep holes that I had plugged with hand whittled pieces of kiln brick. The steam would condense back to water on the the stainless steel casing around the kiln. The pressure gauge on the propane tank read about four and a half pounds.

An hour later, the pyrometer still read four hundred and fifty degrees. Steam was still pouring off the kiln, and could be seen rising from any exposed brick surface. Julie and I kept peeking in through the vent in the lid, to see how our pieces were doing, afraid that the glaze would be 'steam cleaned' off of the pieces. The propane tank was cold to the touch, and water was condensing onto its walls.

At about an hour an a half, the steam rising from the vent hole dropped considerably, and the temperature slowly started to rise. Frost and frozen water droplets covered the propane tank by now, and the pressure was starting to drop. By the time we reached a thousand degrees Fahrenheit, the pressure was down to two pounds and was dropping rapidly. The kiln was stalling. Killing the gas, we swapped out the propane tank for a half full one on our grill, re-lit the burner, and continued firing.

As we cleared fifteen hundred degrees, Julie and I would take turns going out every five minutes to see how the firing was commencing. We were also watching the Eagles game, and were a bit distracted. I went out for what I expected to be the last time, after we had cleared seventeen hundred degrees, and discovered that a spot weld holding the metal strap to the stainless steel sheath on the outside of the kiln had failed. The superheated kiln brick, lacking any external support, was opening like a flower.

I shouted for Julie, and then ran for the garage to try find something to hold the kiln together. I worked sixteen hours of overtime this week, and have been mentally preparing myself for a meeting on this coming Tuesday for the last four days, so I had a little bit of trouble identifying what I could use.

Julie donned her kiln gloves, and carefully pushed the kiln bricks back together. She then turned down the burner, since we had reached temperature.

I finally ran back outside with a spool of electrical wire and a pair of cutters. Donning my kiln gloves, I started stitching lengths of wire through the holes along the edge of the stainless steel sheath, while Julie held the steel back into position. We placed two heavy wires in place, figuring that we could add more once the kiln cooled.

Killing the gas, we grabbed our tongs, and working together, used them to open the lid of the kiln. We alternately pulled pieces from the kiln, each piece glowing a cheery orange hot, and some of the molten glaze mirror smooth, and placed them into individual reduction chambers, then sealed the lids. Two of the pieces had Seth's, so had to be 'flashed', which allows air back into the chamber, and the greasy yellow smoke from the burning newspaper inside 'woofs' into a ball of flame before the lid is slapped back down.

We placed the second load on top of the kiln to allow the pieces to start warming up (two rockets, one wide bowl). Julie opened up the reduction chamber with her dragon vase, and was very pleased with the results of the re-fire. There was lots of copper-penny on the piece, and some patches of blues, magenta, +and purples.

My smallest rocket, which was a re-fire reducing in an unused paint can, also turned out very nice, with similar colors as Julie's dragon, but with a shiny instead of a matte glaze. The previous firing had left the piece an unattractive, blotchy green, but now it looks much better.

The new rocket is dark red with matte black fins. The three engine bells start off copper around the base then transition to a metallic green near the mouth of the bell. The rocket has little canard fins in the mid-body. Its very striking.

The final rocket turned out great as well. The Seth's had some very nice effects on the belly of the rocket, a pearlescent appearance with golds, metallic light blues, pinks and yellows. The rocket body had a higher thermal mass than Julie's dragon, so held onto more heat when before I flashed the piece than the dragon had. The increased heat effects the thickness of the oxides that form on the surface, which results in the colors maturing differently.

We reloaded the kiln, and started firing again. We were up to twelve hundred degrees within minutes, when it started to rain( fat, heavy drops ). We decided to stop firing then, and killed the gas to the burner. I fetched our largest umbrella, and Julie held it over the kiln when we opened it up to allow the pieces to cool. We brought everything back into the garage to wait for tomorrow night, except for the four finished pieces.


Post a Comment

<< Home