Help: resin leak from silicone mold

Spidey83

Active Member
RPF PREMIUM MEMBER
So I recently made my first silicone cast and have had leaking of resin from the mold. I ensured it was tight but still have a leak. Does anyone know an easy fix for this. Now the mold is about 40 lbs and is a two part mold. Just curious if there is an easy way to seal where it is leaking from to keep it from leaking out continuously. Thanks
 
Generally, you are supposed to clamp the two halves together and apparently that seals the molds. However, after losing so much resin to leaky molds, I designed mine to act like a bowl and plug.

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Given you guys have already invested money into making molds, the last thing you want or need to read is to make a new mold, so is it possible to modify your existing molds by building up a wall around the join?
 

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I cleaned my molds today. I scrubbed them with a toothbrush and acetone/alcohol. Seems to have done the trick. Maybe a super thin layer of resin cured and created a seam.
 
Hot glue.

I don't know if this will work for you molds, it will depend on the way you designed them.

On these molds I only needed a part of the master and did not want to mold the whole thing or cut up the master.

This is the bottom of the mold. I wrap packing tape around the sides of the mold and stick it to itself. Then I plug the hole with hot glue. While the glue is still hot stick packing tape over it and secure it to the tape on the sides. It works great, but I have to redo the plug for every casting.

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This one is similar, but I turned the hole into the pour hole. This one is a bit tricky to get a good seal, but it works.

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You need more space around your part. Your Part is WAY too close to the edge.
Hopefully, you are not planning on casting very many. You could try making a quick plaster jacket around your existing mold, if you can get the master back in it, or try it with a casting.
There is a reason we use fiberglass or plaster as a mother jacket for large molds. Also saves on Silicone.
Good Luck!
 
There is a reason we use fiberglass or plaster as a mother jacket for large molds. Also saves on Silicone.
Good Luck!

So does the fiberglass stick to the silicone or do you make keys for alignment? I want to learn how to do these types of molds.
 
I run vaseline around the edges of both sides of the mold -helps to seal the small gaps and I don't (usually) have a problem with leaks.

Hope this helps.
 
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