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Picture of How to Make a High Temp Silicone RTV Mold
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These techniques will work for pretty much any pourable mold-making material (although with urethanes you will need mold release), I just happen to be using high-temp silicone because it's what I have, and I have it because I can cast pewter (and other low temp alloys) with it. You would also be able to use this method to make waxes which you then cast using investment and more conventional metals (gold, silver, etc.).

The pictures of pouring are from when I molded an aluminum flashlight reflector, and the mold pictured in the last step (and this step) is one of my ring molds

Step 1: Materials

Picture of Materials
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You really don't need all that much stuff to make a mold.

- A part to make a mold of
- Mold Max 60 Rubber (available from Smooth-On), or any other RTV (room temperature vulcanizing) rubber
- A mold box (can be any watertight container that fits your part)
- Clay for the sprue
 
To gg1220 ,
I don't know if it's just me being stupid but could you explain how you got the ring shape in the mold, from the pictures and how you explained it, i cant quite figure it out and was wondering if you wouldn't mind helping me out. Again i don't know if it's just me or not.
Thanks Daniel
I'm with Daniel. After viewing this instructable, I am still not clear about how to make a mold for a signet ring.
gg1220 (author)  David4151 year ago
Hopefully this image helps. The ring is mounted on a sprue which is then attached to the bottom of a small sealed container. Here I'm using a 3 oz. cup because it's pretty much the perfect size.
Mix and pour the rubber so it covers the entirety of the ring plus about half an inch. After the rubber cures, peel off the paper cup and cut the mold in half as you see in the last step of the Instructable. 
Hope that helps. Let me know if you need more information!
Ring to be molded w. annotations.jpg
gg1220 (author)  dannywilde942 years ago
Hey Daniel, sorry for the confusion. I had already made the ring mold prior to this Instructable and unfortunately didn't take pictures, so I showed how to make a mold for the reflector just to show the general process.
For the ring in particular, I molded it upside down from what you see in the picture. I attached the top of the sprue to the base of the ring, and the bottom of the sprue to the cup, and then poured the silicone. After cutting the mold open and casting with it a couple times, it was clear that I needed air vents, so I just cut those channels with an X-ACTO knife.
Hope that helps!
grunt16123 years ago
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