Cate Donoghue Posted November 27, 2011 Report Share Posted November 27, 2011 I have a wonderful book on mold making. I've watched videos and looked around for this, but I'm stumped. Normally, in making a two part mold, you bury half the original in clay, pour plaster, coat the first plaster piece with release (after keying it), remove the clay "bed" the held the other half and cast the remaining piece. However, all the articles and books etc like to demonstrate with things like plasticene and found objects. How do you bury clay in clay without destroying it? Do I just need to remake it oversized and fire it first? Or am I missing something obvious? Thanks guys Cate Link to comment Share on other sites More sharing options...
Diana Ferreira Posted November 27, 2011 Report Share Posted November 27, 2011 You can position your piece in the pouring box, making sure that it is laying straight. We normally draw a horizontal line around the article. And make sure that your 'master' is stable. If it is not, you can prop it up with clay/Plasticine, you can also add some weight to the article to ensure that it does not float around. Pour in your plaster up to the line you drew, Once the plaster is set, you can clean up the plaster line with what ever tools you normally use. You can either clean it with the original in-situ, or remove the master before you clean your surface. Add your locks by drilling holes in the plaster with a coin/round object. This piece of plaster will be discarded at the end ... Now you can treat the surface of this plaster mold to prevent it from sticking to your initial cast. Cast plaster over it. now you have your first part of your 2-part mold. Remove the first cast you did, turn the work around so that the last piece you casted is now on the floor. Treat the surface of the second casting you made, and cast the other half of you 2-part mold. You obviously know about undercuts, and allowing a pouring area for your slip ... Link to comment Share on other sites More sharing options...
Marcia Selsor Posted November 27, 2011 Report Share Posted November 27, 2011 I have used things like sand or filling a space with 2x4 segments or bricks in what Diana refers to as a casting box, to support the top half to be poured. Then turn it over and cast the second part. Be sure to make "keys" in the mold so the two parts line up. Just a subtle indent where the flat walls of the mold will meet will work. Marcia Link to comment Share on other sites More sharing options...
Cate Donoghue Posted November 27, 2011 Author Report Share Posted November 27, 2011 Thank you both so very much! I hadn't thought about an expendable plaster piece. I'll give it a try Link to comment Share on other sites More sharing options...
Diana Ferreira Posted November 27, 2011 Report Share Posted November 27, 2011 I will speak to our local modeller/moldmaker, and see if we can collaborate to make a little picture tutorial to show what I described above. Good luck on your mold making, Cate! Link to comment Share on other sites More sharing options...
Cate Donoghue Posted November 28, 2011 Author Report Share Posted November 28, 2011 Thanks Diana! I've made a few molds successfully, but this was doing me in Link to comment Share on other sites More sharing options...
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