MudStuffing Sketchbook

I was back at my parents over the holidays, and noticed a piece of my pottery from about 2 years ago. It was the same temoku glaze I’ve used forever, but this piece had a wonderful radiant amber hue. I started thinking, my current pots are a little duller or muted than this one, what the heck could have changed?

Well last time I went to Highwater, I was checking out the oxides and noticed Spanish Iron right next to the red iron and then it dawned on me. At one time I had subbed spanish iron oxide because they were out of the normal red. I guess I didn’t know much back then, because I obviously switched back to normal red and didn’t think anything of it. It took looking at a two year old pot to notice the difference.

I mixed up a new batch with Spanish Iron Oxide last week and just got my first glazed pieces with it and I couldn’t be happier. Below is what I strive for in my firings, just enough gold microcrystals to give some variation, but not so much that it covers the wonderful glossy amber tone of Spanish Iron Oxide.

Deborah at Sweetwater Designs just put up an interview of me on her blog “Fire & Glass”.

Check it out here: http://sweetwaterdesignsat.blogspot.com/2008/01/i-have-crazy-affinity-for-teapots.html

Deborah does wonderful lamp worked glass beads. You can check out her Etsy shop here: http://sweetwaterdesigns.etsy.com/

Thank you!

Third times the charm right? It was for me. I was working less and less keeping the propane tanks clear of ice, cone 10 was EASY to reach. I also had bought a “cleaning” gun from Home Depot for my air compressor. It’s supposed to shoot out solvents for cleaning. I jerry rigged it up to suck from the pressurized gard sprayer as well as compressed air. I had SERIOUS soda built up and very even distribution. Not one clog.

There was no popping, and no debre after the third firing and I got some really nice wares out of her this time - good enough to sell at least.

I still don’t think I’m getting great reduction. Although I did get some pinks and even a red copper blush on the side of a pot. The kiln fired much more evenl, cone 10 was reached threw out - all flat because I soaked at 2300 for 30 minutes, however next time I need to put in a cone 11 guard cone to see how evenly it’s firing.

So… next steps for better reduction:

I “cast” some new burner ports from porcelain that are the exact dimension as recommended by ward burner systems. I think the previous ones were a little too large. I am also going to seal the door blocks with clay. Previously I had put ceramic fiber to fill the gaps, however I think this still lets in too much oxygen. I check into a oxygen sensor, but they are 800 bucks, a little out of my range at this time.

So to recap lessons learned:

1. DO NOT use permatil in your castable. If I do this again, I will just leave it out if I can’t get P-Grog and it should be fine.
2. Bottom shelf goes ABOVE the flu exit.
3. Seal door blocks with clay.
4. First firing takes awhile.

My original intention was to throw a couple cone 6 glazed pots in there and fire her to 2200 degrees. However, as I got closer and closer to the big day, I opted to fire it empty. I really don’t know the reason why, but I am glad I did.

I started at 7 am and cranked it up slowly. about 150 deg/hr. About 5 hours into the firing tank #1 was pretty well frozen and I was loosing pressure, so I switched to the full #2 tank and let the first thaw. About 1500 degrees, I started hearing “popping” inside the kiln. I wasn’t tooo worried, nothing was in there and the arch is pretty solid. Well the hotter she got, the more it started sounding like a popcorn popper. A couple shot out and hit the house and Gina came out to see what was going on. I debated stopping the firing for a few minutes and then proceeded on. Through the spy and soda holes I could see what was popping. The permatil I had used for an aggregate in the castable was popping out of the castable… not good. Still I proceeded on. About 1900 degrees I had to switch tanks again. this time I filled a 5 gallon bucket with hot water and started pouring it on the tanks every 15 minutes to melt the ice and keep the pressure up. By this time I was up to 7 psi and needed about 8 or 9psi to get it to cone 6. The last 200 degrees seemed to take forever. Between running around with hot buckets of water and switching tanks and everytime I switched tanks, I lost 100 degrees.

I had fired it very slow and was conservative to be sure I didn’t have steam building up inside the castable, plus it had dried throroughly for over a month. Even so, the kiln was also “steaming” and an impressive amount of steam was coming from the arch. All the water was being driven out into the ceramic fiber covering, which at the bottom was dripping wet. The kiln was still popping, although not as bad.

After 10 and half hours of firing, cone 6 finally dropped and I shut her down and plugged her up.

Two days later I peeked inside. There was tones of debrie on the floor. The inside of the arch look bizarre. The permatil castable had melted and “oozed” out of the castable making quite an interesting surface.

Self confidence was eroding by now. It was all I could do to reach cone six - how would it ever reach cone 10? Is it always going to pop and scatter debree all over my wares - will I always have to have a cap shelf and not utilize the whole kiln? Is the kiln going to fall due to the melting permatil? Did I just waste a bunch of money time and labor on nothing? I had gone through 2 propange tanks ($120 worth of propane) which was more expensive than firing the electric.

The last final details seemed to drag on forever. After the arch was cast, door blocks cast and the chimney laid, I covered the kiln with 2 layers of 1-1/2″ ceramic fiber. Then I had some spare white sheet metal that I cut and fabricated to fit over this - maintly to help keep water off.

It was time to set the burners, get the propane tanks and pipe it to the burners. My intention was to use rubber hose, for no better reason than than I didn’t know how else to transport propane from a tank to the burners.

I hit the farm supply store and they were helpful enough to direct me towards copper pipe. I have to say the guys down at Fletcher Hardware they have been wonderful. I went with 1/2″ soft copper pipe and used flanged fittings. Finding the right size fitting proved to be a bigger challenge than I thought as well. As helpful as the farm supply store was, the fittings were in slight dissarray and ended up having all the necessary pieces. See, I have an adjustable high pressure valve with a pressure gauge from my raku kiln. This screws directly to the propane tank on one side. You can get these fairly easily from Ward Burner systems. On the other end is a 1/2 female tap. 1/2 copper pipe. My burners have a 3/4″ male tap. In between I need to split to the two burners using a t. So between all the size changes, I had to get some of the fittings from the propane company down the road, the rest I picked up at Lowes, along with a flange tool. A day and a half later, I had it hooked up like you see in the pictures.

I checked for leaks using soapy water. And then I’ve been checking for leaks by opening the main valve on the tank and then closing it and seeing how long it takes for the pressure guage to read 0. Too much pressure loss and I start searching for leaks with soap again.

Originally I wanted a 250 gallon tank. Unfortunately the propane guy came to spec out the installation and said he wouldn’t be able to permit without a controller. and that I should just go with two 100lb tanks. 100 lb tanks hold about 24 gallons of propane. This is Ok… but as you will see later, I am searching for a “controller” because although two 100lb tanks work fine for a kiln this size, it makes the labor a lot more intensive.

I did a quick 2 hour firing to see how things went before my first firing the next day.