BlackDogPottery Posted November 28, 2017 Report Share Posted November 28, 2017 I was recently contacted by an industrial manufacturer to throw some large-ish planters to create rubber molds from then to cast other materials from these molds. The question is would it more practical to make these from an earthenware than my usual stoneware since they will just be masters? The pros being- earthenware being less risk in firing, less shrinkage (as I mentioned they are big), and overall user friendly clay. My stoneware is funny as in clay memory like an elephant and these are expected to be almost perfect. The con to me is something just doesn't feel right about using the weaker clay as if it wont be "authentic" enough. I'm afraid they might crack during the casting process of pouring rubber but they're pretty thick at half inch wall thickness so is that just being paranoid? Any guidance would be helpful as there's not much out there about the humble home potter working along industry. Link to comment Share on other sites More sharing options...
Min Posted November 28, 2017 Report Share Posted November 28, 2017 Scroll down on this link until you get to the discussion on strength of different bodies. Testing done by Pete Pinnell showed for strength Linda Arbuckle's redart 04 body was the winner. Think there will have to be a compromise between strength and workability plus firing to the clay's maturity. Link to comment Share on other sites More sharing options...
Mark C. Posted November 28, 2017 Report Share Posted November 28, 2017 Since they are just casting your pot-they then can make a solid master from that cast it will not matter what clay you use .That said use the clay that works best for you to throw these from . They will lift only one cast from your clay pots-the rest will come form that casting-master and working molds come from that first casting. Link to comment Share on other sites More sharing options...
BlackDogPottery Posted December 3, 2017 Author Report Share Posted December 3, 2017 On 11/28/2017 at 8:47 AM, Mark C. said: Since they are just casting your pot-they then can make a solid master from that cast it will not matter what clay you use .That said use the clay that works best for you to throw these from . They will lift only one cast from your clay pots-the rest will come form that casting-master and working molds come from that first casting. So do you think I could get by with sending a bisque form? Link to comment Share on other sites More sharing options...
Mark C. Posted December 3, 2017 Report Share Posted December 3, 2017 Yes . I have made molds from bisque forms more than once-They need to be sealed-like clear spray sealer or with a latex sealer.If they sent to master molders they have the stuff to seal them with.The sealer needs to be smooth I have made molds from bisque -wood-high fired forms plaster forms-metal forms-food forms(donuts and bread) and vegetable forms-dog poo Learned all that in school and made most of them later in life.Bisque forms are just fine. I used to do a lot of Raku forms from molds I made-like a bread truck from loaves of bread-I still have a few around or high fire dog poop out of dark brown clay -I'm sure there is some still under our redwood trees in yard . Link to comment Share on other sites More sharing options...
Mark C. Posted December 3, 2017 Report Share Posted December 3, 2017 7 minutes ago, Mark C. said: double post-ops maybe a mod can edit this away-maybe not? Link to comment Share on other sites More sharing options...
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