I've been reading a few books on kiln building lately, trying to figure out something that will work at home without having a full-blown kiln yard in the backyard. Ideally portable, easy to set up, (fairly) easy to fire. Since I tend to make lowfire work, looking at smaller more primitive alternative kilns has given me a few ideas. Mixing that in with modern technology, materials, and know-how should lead me to come up with something. I'm leaning toward a ceramic fiber cylinder (or possibly cube), fired with a propane gas burner or two. Ideally, I'd like it to be able to do a low bisque, and be capable of tinfoil sagger, raku, or horsehair firings. It might end up being a single base with different interchangeable chambers, I don't know. I'm just getting to the point of actually trying to run the numbers and calculations on heat output and retention.
Coincidentally, I ran across this video of an archeological team that found an old kiln site in France and decided to try firing it. The audio is in French, but it's just interesting to watch and follow along as they rebuild the walls and fire it.
The Google translated link so you can read the text is here.
Enjoy!
Showing posts with label raku. Show all posts
Showing posts with label raku. Show all posts
Tuesday, October 19, 2010
Thursday, September 18, 2008
Getting back on track
It's been a week tomorrow since the big wreck, and I've been at a bit of a loss as to what to post. It's pretty clear that I won't be back in the studio any time soon. One of the more painful injuries is a very bruised, very sore sternum. I don't even like to think about trying to wedge or center clay.
I do have some pieces from my failed attempt to re-familiarize myself with the old #112 claybody that are coming through the bisque firings at the center, so I'll be able to glaze them soon. I did take the remainder and wedged it up on the tables and sprayed it down. Hopefully it got a good dose of microbes to help it age. It should be good and ready by the time I'm ready for it again.
I never got a chance to say anything in all last weeks excitement, but I'd thrown in the towel, raised the white flag and went back to my old familiar white stoneware. I'd been trying and trying to get the 112 to work for me, and was just being frustrated. My clay time is precious to me, and I just decided I didn't want to spend my fun time being frustrated and pissed. I threw a 12" vase on the first try.
I'm also spending some time going through old notes I've collected, ideas, sketches, etc. (when I'm not sleeping... I'm doing a LOT of sleeping). Maybe I can get them more organized and possibly share some. And there's been some interest in more details of the naked raku and aluminum foil saggar techniques, so I hope to post more stuff about all that too.
The blog has been up for a little over a month now and I'm having a lot of fun with it. I'm enjoying the community, and have made new acquaintances from around the world.
I do have some pieces from my failed attempt to re-familiarize myself with the old #112 claybody that are coming through the bisque firings at the center, so I'll be able to glaze them soon. I did take the remainder and wedged it up on the tables and sprayed it down. Hopefully it got a good dose of microbes to help it age. It should be good and ready by the time I'm ready for it again.
I never got a chance to say anything in all last weeks excitement, but I'd thrown in the towel, raised the white flag and went back to my old familiar white stoneware. I'd been trying and trying to get the 112 to work for me, and was just being frustrated. My clay time is precious to me, and I just decided I didn't want to spend my fun time being frustrated and pissed. I threw a 12" vase on the first try.
I'm also spending some time going through old notes I've collected, ideas, sketches, etc. (when I'm not sleeping... I'm doing a LOT of sleeping). Maybe I can get them more organized and possibly share some. And there's been some interest in more details of the naked raku and aluminum foil saggar techniques, so I hope to post more stuff about all that too.
The blog has been up for a little over a month now and I'm having a lot of fun with it. I'm enjoying the community, and have made new acquaintances from around the world.
Sunday, July 20, 2008
Naked Raku 102
After the bisque firing, we prepared for the final firing. All of this work took place on the final class.
We coated our pots with a special crackle slip that's made to shrink. This makes it crack up and peel a bit during the firing and smoking process, like a mud puddle in the summertime. It won't actually melt and bond to the pot in the firing, and it will be scraped off afterward. Any larger areas we wanted to be black were left bare. Some people left the rims and collars exposed, or a design on the pot itself.
Then a thin 'glaze' is brushed onto the slip coating. It's job is to try and hold the slip together through the firing. You don't want to get it on any exposed areas of the pot, since it will bond to the clay and makes an ugly blistery mess. Unless that's the look you're going for.
The pots are fired to temperature, which is done more by feel than anything, observing how the surface looks and how the glaze is melting. They are then pulled out and placed in a metal can with sawdust or similar in the bottom. This instantly ignites, and after the flames are going good, an airtight lid is clamped in place. This makes the fire smoke, and this smoke penetrates the clay where the cracks in the slip coating are. After the pot cools, the lid is carefully opened since once air is allowed back in a flare up is very possible if the pot is still hot enough. The still hot pot is sprayed with water which helps crack off the slip/glaze coating now that it's job is done.
We finished by scraping off the slip/glaze coat with metal ribs. After they had dried off the burnished pots could be waxed and buffed with a hard paste wax.
We coated our pots with a special crackle slip that's made to shrink. This makes it crack up and peel a bit during the firing and smoking process, like a mud puddle in the summertime. It won't actually melt and bond to the pot in the firing, and it will be scraped off afterward. Any larger areas we wanted to be black were left bare. Some people left the rims and collars exposed, or a design on the pot itself.
Then a thin 'glaze' is brushed onto the slip coating. It's job is to try and hold the slip together through the firing. You don't want to get it on any exposed areas of the pot, since it will bond to the clay and makes an ugly blistery mess. Unless that's the look you're going for.
The pots are fired to temperature, which is done more by feel than anything, observing how the surface looks and how the glaze is melting. They are then pulled out and placed in a metal can with sawdust or similar in the bottom. This instantly ignites, and after the flames are going good, an airtight lid is clamped in place. This makes the fire smoke, and this smoke penetrates the clay where the cracks in the slip coating are. After the pot cools, the lid is carefully opened since once air is allowed back in a flare up is very possible if the pot is still hot enough. The still hot pot is sprayed with water which helps crack off the slip/glaze coating now that it's job is done.
We finished by scraping off the slip/glaze coat with metal ribs. After they had dried off the burnished pots could be waxed and buffed with a hard paste wax.
Saturday, July 19, 2008
Naked Raku 101
Naked raku gets it's name from the fact it's fired fast in a small kiln, and naked because it's not glazed. I took a class a few years ago and had a blast. Depending on all the variables, you get white pots with various black crackle patterns. Everything from large branches looking like lightning, to thousands of tiny ones.
The recommended clay body was just a standard raku clay that many clay suppliers make. It has a larger amount of grog and/or sand to help it take the thermal shock it's going to get later. Grog is coarsely ground, fired, fireclay. With the sand, it's the 'grit' you feel when you're throwing on the wheel. It s VERY rough on your hands!
The other clay a few people used was a high talc earthenware called Miller 10T. The talc also helps with the thermal shock. Since it didn't have any grog, they were actually able to burnish their pots to a smooth shiny surface. For my first raku attempt, I opted for the raku clay. I didn't want to end up with a pile of shards for my efforts!
As far as throwing, you want to make sure your walls are not too thick, and they need to be uniform thickness. A very thick wall will expand and contract at a different rate on the inside and outside, cracking. The same goes for any thin or thick spots. If you have a thin section going around your pot, it very well could crack around the ring, decapitating your pot.
When the pots were leather hard, the talc people trimmed and burnished theirs, the raku people just trimmed. After they were bone dry, they were bisque fired in an electric kiln to cone 05-06.
Continued at Naked Raku 102 . . .
The recommended clay body was just a standard raku clay that many clay suppliers make. It has a larger amount of grog and/or sand to help it take the thermal shock it's going to get later. Grog is coarsely ground, fired, fireclay. With the sand, it's the 'grit' you feel when you're throwing on the wheel. It s VERY rough on your hands!
The other clay a few people used was a high talc earthenware called Miller 10T. The talc also helps with the thermal shock. Since it didn't have any grog, they were actually able to burnish their pots to a smooth shiny surface. For my first raku attempt, I opted for the raku clay. I didn't want to end up with a pile of shards for my efforts!
As far as throwing, you want to make sure your walls are not too thick, and they need to be uniform thickness. A very thick wall will expand and contract at a different rate on the inside and outside, cracking. The same goes for any thin or thick spots. If you have a thin section going around your pot, it very well could crack around the ring, decapitating your pot.
When the pots were leather hard, the talc people trimmed and burnished theirs, the raku people just trimmed. After they were bone dry, they were bisque fired in an electric kiln to cone 05-06.
Continued at Naked Raku 102 . . .
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