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23 Apr 2013 - 01:10101424
Resin and removing microbubbles
I've been doing some meddling on and off for a couple months to see what I can use as both cheap colourants and moulds for different sized gems alongside trying to make a few custom moulds from 2 part food grade silicon. It's been interesting and enlightening.

What I am getting though is tiny bubbles in some of the finished casts; I figure one or two are unavoidable. In my last batch, which were cast in a cheap artists paint mixing tray, I have what I can only describe as a fairly obvious 'halo' or ring of them at the top of each gem.

I'm guessing heating the moulds before and possibly the resin after pouring would be the ideal method to deal with this, but thats obviously a problem with a cheap plastic mould!

Is it going to be one of these things where I'm just going to have to suck it up and make silicon moulds for everything to get the better result?



Last edited by Junta (23 Apr 2013 - 01:10)
23 Apr 2013 - 06:48101427
at work we make a lot of our moulds for casting shiny resin parts in out of platinum silicone.

If you mould an object that is already shiny and polished your mould will come out with the same surface texture, so anything you pour in it will come out all lovely and clear with a shine to it without any extra work needed.
We also heat our moulds up before hand - putting the silicone into the oven for about 30minutes at 60-90C (depending on silicone and resin) and then pour the resin in, no bubbles or milky textures.

Hope that sort of helps, sadly its one of those things - pay for good moulds, get better product


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23 Apr 2013 - 09:14101432
Cheers for the quick response! Better results in anything usually need better base materials/cost more money, so pretty much what I expected

On the upside I do still have around a kilo of the silicone so I should probably get on with using that up. On a related note though, if the original I'm using to make a mould isn't shiny and I don't care about the object afterwards, is it possible to say varnish or acrylic spray it and get a smooth finished piece that way?


23 Apr 2013 - 10:31101435
You can also try tapping the moulds before they set, this should help any air bubble rise to the surface. In thick liquids they can get trapped, so lightly hitting them will help shift the bubbles up.


23 Apr 2013 - 11:32101436
A friend who makes Lantern Rings from Resin uses a compressor for getting bubbles out.


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23 Apr 2013 - 14:56101442
Quote Junta:
is it possible to say varnish or acrylic spray it and get a smooth finished piece that way?


I've tried that before with acrylic spray and it worked just fine.


25 Apr 2013 - 23:00101568
pouring can be a big factor too, you want to create a long narrow stream of resin to enter your mold, this will stretch and open some bubbles as you go,

also do you vibrate/ tap your molds after? this can bring bubbles to the top

putting the piece inside a vacuum would pull bubbles to the top and burst them, but obviously you would need to make something to be able to withstand negative pressure


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