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Resin getting bound to silicone

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Resin getting bound to silicone

Postby Resinero » Tue Apr 26, 2016 4:16 am

Hey There! I've some trouble casting Smoothcast 310 resin into my Moldstar 30 (platinum silicone) molds, usually goes well but i don't know why sometimes the resin gets bounded to the mold, so it gets absolutely ruined when demold... this never happened to me when i was using tin based silicone but since i'm using the platinum silicone this issue keeps happening to me :(

At the beggining i thought it was because the talcum powder then i went to spray release, so I already using Ease release 200 as mold release agent (Mann) giving a small coat leaving like half an hour to dry before cast but this keep happening.

Does anybody knows why is this happening? I really would apprecciate your help!

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Re: Resin getting bound to silicone

Postby mangozac » Tue Apr 26, 2016 7:26 am

How bizarre! How many casts had you pulled from this mould before the damage occurred?
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Re: Resin getting bound to silicone

Postby Resinero » Tue Apr 26, 2016 8:29 am

Very few casts :S, It's the master mold but i managed to make enough copies in order to make a bigger mold.
I've been searching on the internet looking for some answers and i think i've found the problem, due to the very small mixing quantities i use to mix for this small parts (less than 2g each part) probably i've made a mistake in some point with the proportions. Tomorrow i'll be doing some new tests to check if that's the problem...
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Re: Resin getting bound to silicone

Postby mangozac » Wed Apr 27, 2016 7:14 am

How big is the hand in your photo above?
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Re: Resin getting bound to silicone

Postby Fleafa » Wed Apr 27, 2016 11:46 pm

Resinero wrote:probably [...] a mistake in some point with the proportions.

I think this is likely. A couple of areas where setting is incomplete.
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Re: Resin getting bound to silicone

Postby Resinero » Fri Apr 29, 2016 2:43 pm

I'm making some test and seems like that was the problem, measuring in so little proportions is difficult and not so accurate so i think i'm just mixing about 10-20 gr+ or so to avoid this problem, the hands are very tiny. Soon i will show you pictures of the cast to show you the results :D

by the way, a useful tip. I've realised some small differences when the resin cures well and when isn't propperly cured. Seems like when goes wrong the final cured resin has a oily finish, and that's when the problems are coming >,<. I suggest to make a test when you are measuring small portions of resin and try to mix by volume and not weight, because is easier to go wrong this way in so small proportions.
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Re: Resin getting bound to silicone

Postby mangozac » Sat Apr 30, 2016 9:11 pm

Do your scales measure to 0.1g? I regularly mix down around 10g (of each resin part A and B) and don't have any problems. If you need to mix more than just make sure that you fill multiple moulds at a time ;)
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Re: Resin getting bound to silicone

Postby dce1511 » Sun Dec 25, 2016 10:52 am

I received a bad batch of Smooth Cast 325 once. Part A of a 2 Gallon batch had a leak in the spout straight from the manufacturer. No telling how long it was exposed to the elements, but it stuck to the silicone like crazyglue, ruined several very valuable molds, in spite of pretreatment with Manns or Dry release agents. Molds where made from Platsil 71-20 and Pour-a-Mold, and castings ranged from 30cc to 120cc. So size was not a factor with mine.

Tried soaking in wd40 to see if it would penetrate and loosen the casting, but no luck. Never saw it before or since.

Surprised that both your and my experience occurred with Smoothcast products, but don't know if that was a factor or coincidence. Platnum was also involved, at least with the Platsil (not certain what the base is for Pour-a-mold)

Some of the molds were one of a kind and very difficult to remake. Very frustrating.
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