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  1. Its a commercially made glaze. So I don't have the formula for this glaze. I'll try adding some Kaolin. Thanks for the help.
  2. Okay, guess I miss read that about the spudomene. If I don't have any china clay, is there a substitute?
  3. I am a high school teacher and I found a beautiful commercially produced Turquoise glaze that tends to run, a lot! I have never relly gotten in to the chemistry of glazes. I have always used prepared commercial glazes. Simple, easy to mix and cheap. My question is, what can I add to the glaze to reduce the amount of running? I believe that the running is a result of firing the glaze to too high of a temp. However, if I fire to a lower temp to keep the Turquoise from running, the other colors will not fully mature. With so many students, I don't have the capacity to do a firing of just the Turquoise glazed projects. My little research says that by adding China Clay to the glaze it will reduce the runnyness (not sure if that's a word). I also saw that Spodumene will raise the melting temp as well. Any help is greatly apprecioated. Brian
  4. http://community.ceramicartsdaily.org/topic/6114-pizza-stone/?hl=%2Bpizza+%2Bstone Found the page with the thread, listed above if anyone is interested. Thanks
  5. I had a friend that was asking if I could create a pizza stone for use with his bbq. I work mainly with stoneware and always felt that putting my ceramics over an open flame would cause cracking or breakage. Has anyone created a pizza stone? what type of clay worked best? Thanks, Brian
  6. Thanks Mark. Just trying to to avoid reinventing the wheel. I appreciate the info. Brian
  7. So, does more water mean a softer mold or harder mold? I am only making one mold at a time. Only mixing around 2 lbs of plaster at a time. With the smaller amount of plaster I understand that the water: plaster ratio will be much more sensitive. Agian, trying to avoid the years of trial and error.
  8. Greetings all, I have been making mugs with tiki faces carved in them. I have made molds that have been working so I can reproduce them fairly quickly. The problem is that the molds chip very easily, leaving holes in the mold which then create unwanted that then have to be smoothed out after the pouring and drying. My question is: Is one plaster better or more durable than the others? I have been using pottery plaster #1. However, at my ceramics supply company that I order from I see that they have a number of different types of plaster: Plaster, Hydrocal White with 4500psi compression strength Ceramical Gypsum Cement with 6500psi compressions trength Puritan Pottery Plaster with 2400psi Compression Strength Pottery plaster #1 has a 2000psi compression strength. I'm going to go out on a limb here and guess that the higher the compression strenght, the harder the plaster. If someone could confrim this, that would be great Second question: Who has used a "harder" plaster for mold making and what are the disadvantages or advantages you have found? Still kind of new to the mold making and production process and trying to avoid the years of trial and error, so any information would help a bunch. Thanks, Brian
  9. Anyone have a fromula for making thier own kiln wash? I usually just by the prepared kiln wash from my local supplier, but relized I was out and need to do a glaze firing for my High School kids. I don't dare do a glaze firing without kiln wash! Thanks, Brian
  10. Been using Sodium Silicat mixed 50/50 with water, per the manufacturers directions.
  11. I have mixed the slip according to the manufacturers specs. With a specific gravity of 1.76. I have tried 1.79 and also 1.72 spec. gravity and have been having similar results. The Slip does tend to "settle" or dry quickly. If I leave it for an hour or so, there is more firm "skin" layer that develops on the surface, usually about 1/2" thick. I just mix that in to the slip and strain it before pouring and it doesn't seem to be effecting the consistency of the slip. The molds are dry and slightly warm to the touch, similar to a bone dry piece of clay. Perhaps I need to leave them dry for longer than 24 hours. The humidity has been a little hi over here in Southern Calif. I am fairly new to slip casting, so any advice is appreciated.
  12. I have tried letting them dry over night, and that didn't work. The details caused it to crack and tear itself apart. I have also tried letting them dry for about 1 hour until the slip was leather hard, or slightly beyond, and still they stick. Is just a matter of finding the ideal drying time through trial and error?
  13. I have been making slip castings of some mugs with Tiki style face carved in them. I made sure to have no undercuts so that they would release from the mold. I had a Cone 10 clay body (Soldate 60, for those familiar with this body) that I was using to make slip from and it seemed to be working just fine. I started using a store bought Cone 06 Clay body that has no grog so I could get a smoother result and also use the brighter colors of the low fire glazes. My problem is that I am having difficult with the leather hard slip releasing from the mold. The molds are 4 piece molds and made from the same plaster that I was using with the Soldate 60 and having no sticking problem. Any suggestions would be welcomed. Brian
  14. Hey all, I have been making some slip cast mugs and I keep getting bubble that form on the inside of the mugs. After I pour out the slip, when I look on the inside of the mold, I see little voids from what I can assume are bubbles in the slip. They range from about 1/8th inch to 1/4 inch. I can smooth them with a loop tool, but this is pretty time consuming. I do vibrate the molds with a vibrating sander after the initial pouring for about 30-45 seconds, but after that I just keep the slip topped off until I'm ready to empty the slip out. Any suggestions on how to get rid of the bubbles? Thanks, Brian
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