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About mrcasey

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    As far as ceramics go, I'm interested almost exclusively in hand building slab pots for bonsai. I'm looking to create traditional forms with very simple geometries.

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  1. I've got a half face mask with N95 rated cartridges. I used to just mix in a tiny kiln room with a standard exhaust fan. After reading a little, I've discovered that many people consider a kiln exhaust system to be inadequate for glaze mixing ventilation. I've read a couple of posts from John Baymore where he mentions the difficulty of designing one's own adequate vent system.
  2. In our community art center, we've been building a room in which I can mix glazes. I probably spend about 5 hours a month mixing and I'm curious to know just how much silica I'm exposed to. Does anybody have any advice about the buying and use of the cyclones (I think they're called) used for this purpose?
  3. When I began wheel pottery, I got the impression that most throwers started bowls from cylinders and I've always taught bowls that way. But a lot of good potters I watch on you tube don't actually start bowls from cylinders. Right off the bat (no pun), they start a concave curve in the floor of their pieces and they don't pull up vertical walls. When you guys teach bowls, do you start from an exact cylinder, or do you start from a kind of "V" shape with a curve already in the bottom?
  4. This week, someone donated a number of old glaze pigments to our community studio. Some of the jars in which the pigments come have labels; some don't. The jars with labels have the names of chemical companies and the names of the stains. Some also have dates of manufacture and a few of the elements in the stain. However, none of them have the specific chemical formulae of the active ingredients. Because some of the manufacture dates go back to the late 40's, I'm concerned about use of dangerous ingredients. In particular, I'm concerned about lead, barium, cadmium, a
  5. I understand that the thermal expansion of the glaze being greater than that of the clay body results in crazing, but I'd like to be able to give my students a visual model for what's going on. What do you guys think about the analogy of a hot bowling ball with mud on it. As the bowling ball cools, it will shrink just a little; as the mud dries, it will shrink a lot. The mud will try to shrink down but pull away in some places creating little cracks. I realize the analogy doesn't quite work because the mud is shrinking because evaporation and not cooling. What do you guys think?
  6. A few of my friends in our community studio have purchased small containers of "flux". The flux is meant to be brushed over or under the glaze. I'm the glaze maker and a few people approached me about making our own. It's cone 6 stuff and I just figured it was probably water, frit 3134 (or something similar), and a little bit of clay. Has anyone experimented with this stuff and/or made up their own recipe?
  7. I suspect that this stuff was never actually used in our studio. I further suspect that it was taken from a local community college's larders when their ceramic art program was shut down.
  8. I recently found an old abandoned box of standard overglazes in our studio closet. We only fire to cone 05 and 6 electric. My understanding is that these overglazes are applied after the glaze firing and then fired to a very low temperature. The info on the containers is kind of vague about cone temperature and application. The digital fire pages says that some overglazes or onglazes are fluxed with bismuth and will melt at around 1300F! Maybe I could use them in pit firing? Can anybody tell me a little more about these "overglazes" and how/why someone might want to use t
  9. I've spent the entirety of my time as a potter using various cone 6 stoneware. In our studio, we have access to a white body (Laguna #65). What is the advantage, if any, to switching to a cone 6 porcelain?
  10. A member of our community studio would like to mix up a batch of Patsy Green 2 from John Britt's mid fire book. The lithium concerns me as does the 4% copper. I don't have glaze software to look at the limits and I was wondering if somebody could run the numbers for me. Also, I'd be interested in anyone's opinion about the safety of the glaze. Neph Sy 44 Silica 18.9 Whiting 7.9 Kaolin 2.3 Dolomite 5.6 Gerstley Borate 12.8 Lithium Carbonate
  11. What is the error range on such a scale? 1/2 gram maybe?
  12. I broke the hydrometer so I'm using a 100 mL graduated cylinder and a Harbor Freight electric gram scale accurate to .1 gram.
  13. I'm going to make things a little more concrete. Matte Gray Glaze Custer Feldspar 6 % Silica 8 % Wollastonite 20 % Kaolin 40 % Frit 3134 12 % Talc 14 % : 100% Mouse Gray M. Stain 8 % Bentonite 2 % This stuff is the thickness of wet concrete. Today, I added water till I got down to a 1.25 specific gravity. It is still crazy thick - thicker than heavy cream. Can I just keep adding water? Should I deflocculate? Panama Blue Custer Feldspar 44.1 % Silica 15.8 % Whiting 2.6 % Kaolin 2.6 % Dolomite 7.7 % Strontium Carbonate 4.2 %
  14. Recently we changed bentonites and our newly mixed glazes look way thicker than they used to even while I'm adding more water. The specific gravity measurements are a little lower than they used to be and the glazes look flocculated. Is it possible that a watered down glaze could run more, simply because it's over flocculated or had too much bentonite added? All of this seems very counterintuitive to me. I always kind of assumed that for a given mass of glaze material, adding water would thin the glaze and make it less likely to run. Taking out water would thicken it up and make it
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