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fergusonjeff

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  1. I agree with Neil. My standard cone 6 mix is 1/3 each of speckled stoneware, red stoneware, and porcelain. My cone 10 wood fire mix is 1/2 course stoneware (Rods Bod) and 1/2 various porcelains (some commercial, some home-made). The mixes all throw and fire better than any of the individual clays. I did have a light colored cone 5 stoneware once that bloated a lot at cone 6, even when mixed with other clays. I am still thinking the mixture was bad. Took a while to get all that bad cone 5 clay through my mixes.
  2. I am currently using fiber boards as dampers on my wood kiln. I got them along with some kind of liquid (I think a silica) that I painted on the boards heavily. After drying they are pretty strong. I have used the first set about 4 times and they do warp a little but have remained intact after 12-hour cone 11-12 firings. I would prefer to use kiln shelves but not sure any can handle the temperature differential across the shelf. I have used 1/2" thick steel plates, but these warp and degrade quickly.
  3. What type/model of pug mill is it?
  4. I use that same clay for Cone 10 wood firing. You are basically just talking about bisque temps. It is definitely not waterproof at those low temps. I doubt the low-fire glazes would fit well enough to provide any good protective layer. The speckles in Rods Bod are mainly from iron, and they take the high temperatures (like cone 10) to develop. My bisque fired rods-bod (what you are planning) is just an off-white color and very absorbent.
  5. The analysis we do just provides a compositional profile - usually about 33 elements. Determining the origin is where it gets complicated. You would need lots of known samples from potential sources and hope that the recipes are internally consistent (from the same source) and there is clear distinction between sources. Ceramics do not work like obsidian. I do a lot of work with obsidian (stone tool) sourcing as well, and in that case we can usually directly match an artifact to a specific geologic source. Clays are way more complicated. As a side project, we recently completed a d
  6. If you are really interested in a large-scale study, and have lots of money to throw at the analysis, then you could always conduct neutron activation analysis through my lab. In reality, this would be a pretty expensive proposition, but you might like to look at the lab website just to get an idea of what a study like this could entail. My day job is as an archaeologist with a partial appointment in the lab. archaeometry.missouri.edu There are some other analytical options (such as XRF or ICP-MS), but they have generally lower precision and accuracy.
  7. I have had a SS Peter Pugger for about 5 years and used almost daily. Not a speck of rust or corrosion. I use some porcelain in my mix also. I am interested in hearing how your situation turns out.
  8. I use hardwoods (mostly oak scrap from wine barrel and pallet making) early in the firing when I am looking for a slow steady climb, but in the later stages the hardwoods just burn too slow to maintain or increase temps over about 1900 degrees. Hardwood (especially oak) ash also takes longer to melt, so switching to pine for the last few hours helps reduce crusty ash buildup on the pots. Flame length can also be an issue. Pine has a shorter burn length. I have a smaller single-chamber wood kiln, so it does not matter much, but it could be harder to heat the back of the kiln the s
  9. In a hurry this morning, but I am pretty sure this is the video that shows how to break the seal between the vacuum chamber and the mixing chamber. Not sure if just pasting the url will work.
  10. My new favorite pots are tea bowls thrown with lots of decomposed granite (from bags of chicken grit from the feed store). Works really well in cone 10+ wood fire. the granite chunks are mostly between 1/8 and 1/4 inch in diameter. Throwing is not too bad, but trimming is tough.
  11. CactusPots. I think you might be a little confused. With the peter puggers, the initial vacuum pull usually seals the back vacuum chamber, but not the mixing chamber. I usually have to start pugging for a few seconds before the seal between the mixing and vacuum chambers is broken. then turn back to mixing as the mixing chamber vacuums down. If the cap is not on while the mixing chamber is under vacuum it will not seal. I tend to overfill the chamber so as soon as you turn on the vacuum it pulls a little clay through the gap between the chambers and seals off the vacuum chamber. Startin
  12. Don't underestimate the value of a pug mill. It is expensive if you only think of it in terms of recovering scrap. If that were the case my pug mill would take about 15,000 pounds of scrap to break even just on the cost of the clay, not including the labor of pugging. The real value is in being able to mix clays and to get them to the right consistency for the particular task. I make about 1/2 cone 6 electric fire, and 1/2 cone 10 wood fired work. I mix mostly commercial clays for both temperatures. I like some speckle in both, but commercial clays either have too much or too little
  13. I get the same blue color from white clays in my PP. I asked the company and they said it is just a harmless reaction of clays with the dyes in the cap. I burns off with no issues. Something green that sticks around through the firing is something all together different that I have not seen.
  14. I don't use cones in my regular electric firings, but I do in wood firings. My higher temp cones (9-12) bend backwards at the tip first then drop forward. Provides a nice early warning.
  15. I have both a new Thomas Stuart and a shimpo whisper. I can definitely cause a little slowdown in the whisper with larger amounts of clay, but most items are under 5 pounds and it is not really an issue. I end up throwing 95% on the whisper for two reasons: 1) it is in a better spot (had it first) and 2) the wheel spins freely when the pedal is stopped. I find it really annoying to have the wheel stopped and not be able to spin it with the stewart.
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