How to Make a Rubber Urethane Mold for Casting Starfish

Here's my tutorial how to make a rubber urethane mold for Casting Your Very Own White Finger Starfish.

starfish rubber urethane mold
Now, why would I want to cast starfish when I can buy real starfish for as little as a buck a piece (or even less)? Well, the fact that these pretty animals are harvested alive for decor purposes just makes me cringe, therefor I don't buy starfish (nor shells or any other sea life). If you feel the same, you'll love this project.

urethane mold rubber
What you'll need is Urethane Mold Rubber (comes in two parts) and Mold Release Spray.

how to make a rubber mold
Then you'll need a flat frame or box. Husb made up this simple wood frame. I have three finger starfish that I received as a gift (see Sparkling Glitter Crafts). One of the starfish was a perfect model. Flat and nicely shaped. Turned out the square rubber mold was a bit stiff which made it hard to release the cast starfish, so I ended up cutting away lots of material.

make a rubber mold
Apply plenty of silicon sealer around all the starfish fingers so the rubber urethane mold will not undercut. Try to align with the outermost edge of the starfish, then it will be easy to release the cast starfish. And as seen in the previous picture, coat everything with mold release spray. Be very generous.

how to make a urethane mold
Then, mix the two parts of rubber urethane mold together and pour until starfish is covered. Let dry over night.

mold making
Release time! Disassemble your frame.

how to make mold
And lift off the rubber mold.

starfish mold
Success!

rubber starfish mold
And after cutting away all the extra material, I have a perfect rubber urethane mold to cast as many starfsh as I wish.

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