05/29/2009 (3:57 pm)
Carved Fridge Magnets #2 - Making the press molds
This post demonstrates how the plaster press molds were made for the fridge magnets that were started in the last post. When we left off, I had just finished making the models that I wanted to mold.
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First things first. I stuck the models that I wanted to mold to a piece of plastic coated MDF. Then, I rolled out some clay coils and flattened them with a small roller. These were wrapped around the models to form walls, leaving about 1/2″ of space between the model and the coil walls. |
| Note that the board is wet where I’m sticking the coils down. Pressing the flattened coils onto the wet board gave a nice, firm seal to prevent plaster from leaking out the bottom.The clay was left to firm up for about an hour. | |
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Mixing the plaster. The plaster powder was added to the water and allowed to sit for about 15 minutes, then gently stirred by hand until it was the consistency of thick cream. Mmmm… yummy. |
| I don’t have the picture here, but as I’ve said before - successful plaster work requires preparation! I had my plaster cleanup bucket, a plastic-bag lined container, and sponge right there, for a quick cleanup after pouring. | |
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The plaster was gently poured into the casting forms. Pouring gently helps prevent annoying and evil air bubbles from forming on the surface of the mold. |
| Next - a fast cleanup! I had my plaster wash bucket on the table and when the pouring was finished, everything was cleaned up right away. It doesn’t take long for plaster to set up and ruin your stuff, so be prepared! | |
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The molds were allowed to set up for about an hour. |
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Once set up, the clay forms were removed from around the plaster molds. It was as simple as pulling the coils off the edges, and gently knocking the molds to loosen them from the board. |
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Here’s the mold turned over. You can see that the mold is the reverse impression of the model that was carved in the last post. |
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I used a rasp to clean up the edges, then sponged the mold out with clean water. |
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The molds will be completely dry and ready to use in about 24 hours. |
In the next post, I’ll demonstrate using the press molds to make the magnets.
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