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Bryan Johnson

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About Bryan Johnson

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  1. colouring large batches of porcelain

    For that size batch I like using a stainless steel Peter Pugger VPM 9. How I prepare the colorant depends on what it is. Some I ball mill, some I blend, some just get put in the PP with water. Starting with a 25% batch makes a mix that can be added to a white base with 1# adding 1%. I like using a progression of colors and shades so that what is left in the mixer adds to what I want. Something like dark blue to light blue to blue green to brown to tan, maybe clean it out and then yellows to orange. I run the clay through twice to get the clay in the nozzle mixed in. The vpm 9 leaves about 8#s in the nozzle, about half of which can be extruded before it is mixed with the new color. I find the density of de-aired clay much better for polished work. This might be some what dependent on the clay.
  2. Soldner Mixer Drum Repair

    Having a sealed surface made no difference in mixing. Cleanup might be a tad harder as not as much clay peeled off of the walls and floor. The concrete seems to be stable, with no cracks, old or new.
  3. Soldner Mixer Drum Repair

    The reason that I had low vis epoxy was because of some boat repairs that I had been doing. The epoxy retailer said ( after I already had it) that lo vis had been developed for concrete repair. The kevlar I found on ebay in a 1' wide strip. I only had to make one 1' cut. Cutting kevlar is a real pain! The finish top coats were thickened with kaoln, thanks to wikipedia. The epoxy barrier paint's description makes it sound like they used kaolin for the thickener as well. Sanding kevlar mainly makes fuzzy lumps. A big sharp chisel will take off errant threads and bumps.
  4. Soldner Mixer Drum Repair

    Here is a picture of the fixed mixer.
  5. Soldner Mixer Drum Repair

    The drum on my soldner mixer was cracking, with some small pieces falling out. I worked low viscosity epoxy into all of the cracks. Then covered the outside with two layers of 10 oz kevlar and epoxy resin. Mixed several batches today. Having sealed the inside surface didn't seem to make any difference in the mixing process.
  6. Coe Study / Clay

    Nerd How are you determining COE of clay bodies? Bryan
  7. Can My Sculpture Be Considered A Mug?

    Just tell him "It is a tea pot".
  8. Generally the approach to decreasing plasticity of bentonite is to increase the kaolin, feldspar and silica. Molochite might help too. It could probably be fired and converted to grog.
  9. I would call the Axner Laguna product miss labeled. I like you summary of particle sizes. I have been wondering how NZ Kaolin fits into this picture.
  10. It looks like I need to find a source of calcium bentonite. Pol Ox WSR 5 to 8 million MW used at 1/2 of .1% or .05%. (I was trying to copy and paste a clay art post from Jon Singer, but couldn't)
  11. I'll see if I can find out which it is. It is L10 Have you tried poly oxy ethelene?
  12. I started with bentolite L, switched to Volclay, then to a calcium bentonite from American colloid through Kraft Chemical, sorry I can't be more specific on this. Back to Volclay, seemed to be contaminated with calcite and some black rock. Now I am just starting to use the following, which seems to be European in origin, via Laguna: BentoLite L-10 - A non-swelling Calcium bentonite and our lightest colored Bentonite. Excellent for use in clay bodies, especially in conjunction with Macaloid in porcelains. Typical analysis: SiO2 58-64% Al2O3 19-22% CaO 0.65% MgO 2.5-3.2% Fe2O3 2.8-3.5% FeO 0.2-0.4% Na2O 1.5-2.7% K2O 0.2-0.4% TiO2 0.1-0.2% Moisture 6-12% PH 9.0-10.5
  13. I've been using calcium bentonite for quite a few years. Seems to need 1-2% more, but I've used different ball clays over the years and they have an effect too. Bentolite from Laguna seemed cheaper and easier to get than other calcium bentonite from Kraft Chemicals. I'd like a NZ kaolin based body with 12.5% schrinkage. and so far the closest that I've come is about 1/3 each of calcium bentonite, POE, and v ee gum t.
  14. Slab Roller Experimenters Wanted

    I am not sure just what you are trying to do with printing with a slab roller. This picture is a tile that was run through a Baily with a 3/4 bisqued slab with the image carved into it. The slab that recieved the image was about the right thickness. Sorry 'bout the image quality. Seems like lots of possibilities with thin layers of color and then scraping.
  15. Clear Glaze Chemistry

    What is the glaze like when you refire it? Here are a couple of non-standard ideas that might take advantage of soluble borax. Apply glaze to damp pot and let dry slowly, hopefully encouraging the borax to migrate to outer surface of glaze. Apply a very thin layer of borax to an already fired pot, by heating the pot and then spraying a solution of borax on the surface.
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