Sunday, March 13, 2011

Hot Pour Vinyl Fishies

Materials:  Hot Pour Vinyl, Plaster, Vaseline, Acrylic Paints, Mold Box (wood or other), Modeling Clay
 
The mold for these herring was made for our production of 'The 39 Steps', by our clever and hilarious intern, Jess Smith, with guidance from yours truly.
Intern shown actual size.
 It is a simple two part plaster mold made from a fake fish that we had in stock.  See! Casting and faux foodstuffs in one convenient post!

The Original.
The first thing that Jess did was to determine where the seam of the mold wanted to be. With a symmetrical piece like a fish, this is a pretty easy task, especially when the fish you are using is a cast piece that already has a seam!  Using a wooden mold box, Jess built up clay around one side of the fish, taking up the space that one half of the mold would eventually fill.  Before applying a release agent, she built up clay near the mouth to form a pour spout, and carved a trough with a carving tool to act as a registration.  (A registration is made to keep the two pieces of the mold in the correct alignment.)  Once the clay dam was complete, Jess used petroleum jelly (good ol' Vaseline) to coat the clay dam, the wooden sides of the box, and the fish. This acted as a release agent so that the plaster would not stick to any of the surfaces and prevent the mold from being removed.  Jess then poured the plaster into the first side of the mold, and allowed it to cure.
Here you can see the first half of the mold and the clay dam that has been removed.
Once the plaster set, Jess removed the whole thing from the mold box (some disassembly required), flipped it, and settled in back into the mold box, plaster side down. She then removed the clay dam, built the second half of the pour spout, and gave the whole shebang another coat of petroleum jelly before pouring side two.  Once side two was poured, she removed the mold from the box, removed the fish from the mold, and gave both pieces of the mold a good scrubbing to remove the release agent.
See the registration trough/ridge?

The next step was to pour the castings.  We used pigmented hot pour vinyl to do this (see last weeks post here).  After securing the mold halves together, Jess heated the vinyl until it melted, and poured it into the mold.  The vinyl itself isn't sticky when it's dry, so no release agent was needed.  Then, once the vinyl had cooled, we popped it out of the mold, trimmed the sprue from the pour spout and painted the fishies silver with acrylic paint.  We did try to brush silver bronzing powder into the mold before casting, and while it looked good, the powder came off on our hands too easily when handling the herring- so we went with the paint instead.



The best thing about these fishies is their floppy quality.
video

1 comment:

  1. I love the floppiness of it! It totally sells it.

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