Thursday, September 13, 2012

06 Waste Molds Nº 4

I am waste molding the head next. First of all I have decided to make a one-piece moulage block mold of the head. I am planning on cutting the moulage block mold with my mold knife after it sets up. The mold knife, as I have already mentioned, creates registration keys when it cuts the mold. I made a spare from Roma Plastilina oil-clay and inserted it into the neck socket. Roma Plastilina contains Sulfur, so it cannot be used to make silicone rubber waste molds. It can be used to make plaster waste molds. Click on any image to enlarge it.

After fastening the spare to the molding board, I made a coddle from some cereal box cardboard that is one inch (2.54cm) higher than the top of the head. I also clipped tabs around the bottom of the coddle so it would curve better.

Notice that this time, I have clipped off every second or third tab. This allows the tape to hold the coddle down on the molding board when the moulage is poured into the coddle. Yesterday, I did not do this, and the coddles lifted up, and moulage started leaking out of the bottom of the coddles. I do not have any pictures of that exciting event because I was too busy plugging leaks and scooping up moulage from the table to take any pictures. Fortunately, no harm was done, and as you have seen, the casting came out nicely.

I tried to center the head inside the coddle as best as I could. The head is now ready to be poured with moulage when I get a block of uninterrupted time.

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  1. So undercuts do not matter here as in working with plaster? undercuts are my downfall - and too much flash around the edges. patti

  2. Hot-pour moulage is a semi-flexible mold material, so undercuts are less of a problem than with plaster molds. I can make a one-piece moulage mold, then cut it with my mold knife, and flex the mold off the model. Plaster is a rigid mold material, so getting the parting line exactly right is very important. An undercut in a plaster mold might lock the model in the mold.


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