redbourn

got it. One last question: does it matter what metal I use to make the hood? I read that one person used roofing metal, another used sheet metal.

Thank you so much, Bill. This makes sense and looks quite doable. I'll let you know how we get on!

It will be natural gas.

Bill, you are so generous with your help! If you do this for a living I will happily pay you for a design. What I misread in the charts is that the numbers are per thousands of BTU's. A big mistake! So for 28000 BTU's (yes this is max) I would need a 7 or 8 inch pipe, 6 feet in height. I'm attaching 2 photos of my set up so you can see the roof shape. From floor to top of kiln is 44". From top of kiln to ceiling where it sits now is approximately 75". I've placed the kiln 3 feet from the inner wall but it could be moved a bit so the dimension from top of kiln to ceiling could be taller. I would probably hang the hood from the ceiling high enough that it will work when the kiln top is open, another 30" or so. So from floor to bottom of hood would be 74". The hood and chimney will run straight up through the metal roof with no bends. I live in Huntersville, NC which is 813ft above sea level.

Bill, If your set-up used a 12" pipe and had 800,000 BTU/hr input, wouldn't the chimney have to be hundreds of feet high, according to the chart? Or am I mis-reading it? My kiln is 280,000 BTU/hr.

Many thanks, folks. I will study the Selkirk literature.

Many thanks to both of you. I see how much I still have to learn! I'm going to copy and paste your replies into my notes.

It's a 28" wide olympic updraft, so round. I'll vent through a metal roof. I read somewhere that I need 10" double-walled pipe for the chimney. I assume I can find this through an HVAC place or a woodstove place. I'd like to make a 40" hood for the chimney to fit into--that's what Olympic recommends. I don't think it matters what shape it is as long as it is wider than the kiln. I need to meet code requirements.

Has anyone tackled this? I'd love some info about how you went about making it.

Can you tell from a glaze recipe what it's melt temperature is? I've read about putting a high melt over a low melt and vice versa for interesting effects, but I don't know how to identify the melt temperature.

These are all very helpful responses--thanks! As to the wall piece, I'll take Chris Campbells' suggestion. As to clear glazes, I guess the answer is to test, test, test. Lana Wilson gave us glaze recipes, but she uses a different clay body and different firing schedule than what I have access to.

Hi Friends, I was able to participate in a Lana Wilson workshop recently, where we made slabs with layers of underglazes on top, then scratched through and stretched. The slabs were lovely, and I made a small tray out of half of one of them. Bisque fired it, then applied a commercial clear satin glaze, fired to cone 6. The result was that the glaze made the underglazes run and soften a bit. An attractive result, but with the other half, which is a wall piece, I don't want the softening and running. A potter I met told me she seals her slip-transfer wares with a gerstley borate wash. Would this work for my slab, coated with underglaze, do you think? Other suggestions? I'd like a matte to satin finish. Thanks in advance, Lynn

"actually any form of iron under clear glaze changes in oxidation. if i put RIO on my bisqueware and then apply clear glaze on it, nothing or very little of the RIO will remain on the pot. but if i put RIO on top of clear the colours remain. " Very interesting. Thank you. --redbourn

Thanks to Neil and bciskepottery. I believe she fires in oxidation. Neil, I'm new to all this and so thought the lovely red of the slip would remain. Sounds like I'm wrong.

I recently made and used Mary Barringer's cone 6 redact slip recipe (Spodume 10% Cedar Heights Redart 80% Lithium Carbonate 10% add 2% red iron oxide). I glazed with a Spectrum satin clear glaze. In the glaze firing the slip turned a very nasty dark brown. Any ideas why this happened?