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Cup Molds for Small Castings 
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Joined: Wed May 05, 2010 3:26 am
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Unread post Cup Molds for Small Castings

If you need to make a mold of a small object, the easiest thing to do is to cast it with silicone in a small cup.

- First, consider the size of the cup you will need. Most are wider at the top, and narrow at the bottom. You will probably need to use the top area of the cup, which means that you will need to fill the bottom area with clay. Make sure that your model will fit inside with at least 1/4 inch of extra space all of the way around. If it is too large for a cup, you can also use a bowl. I like to use disposable Ziploc bowls.

- Put clay in the cup or bowl to give yourself a flat working surface. It should be at least an inch below the top of the cup, and should be as smooth and flat as you can make it.


- Gently press the model into the clay. You do not want to bury the edges, you simply want to seal them. Press the model into the clay until there are no places where the silicone can run underneath it. If the object does not have a flat bottom, you'll have to add pieces of clay to seal the bottom edge.


- Spray mold release into the cup. The silicone shouldn't stick, but it's better to be safe and use the release. It will also protect your mold by saving it from wear and tear when you pull it out of the cup and off of your model later on.

- Mix a small amount of silicone according to the directions. Be sure to mix very thoroughly! For this demonstration, I used OOMOO from Smooth-On.

- Slowly pour the silicone into the cup. Be sure to pour it beside your model, not over the top, and allow the silicone to slowly spread across the surface. This will push the air out of the way as it spreads, thus avoiding air pockets. You will need enough silicone to cover the model with about an inch of silicone. You can use less, but it will create a more sturdy mold if you pour in a bit more.

(Note: in this picture you can see that the bottom of the cup is not completely filled with clay. There's no point in filling it completely when you don't have to! Leaving some air pockets makes it easier for you to pull out the clay and toss it back into the bag for reuse later.)


- Allow the silicone to cure overnight.

- Remove the mold and model from the cup. The easiest way to remove the mold is by cutting the side of the cup and peeling/tearing it back. Since the silicone is flexible, you can also gently pull it back from the edges with your fingertips and ease it out of the cup or bowl. Be careful not to tear or damage the mold while you are removing it.

- That's it! Your mold is ready for its first casting to be made!


Pam :-)


Wed Jul 15, 2015 5:55 am
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