2 Part Silicone moulds (Blu-Stuff and similar) reacts badly on 3D printed Resin

[sbarnby71]

I'm a big fan of Blu-Stuff 2 part putty, but recently I saw they only make the liquid stuff.  I bit the bullet and bought some and had horrible results, the surface area that touched the item I wanted to take a mould from was shiny and after a few hours of letting it dry, it was still mushy.  I thought it must be the liquid version and it's just rubbish.  I then bought another brand from Amazon (DecorRom), this is the normal putty which I like.  Took some moulds and had the same issue, but only on some pieces.  Wasted about half a tub of this stuff trying different mixing/setting times (leaving it for 4 days to set) and still it never set.

 

Then it struck me, most of the pieces I was taking the moulds from were 3D Printed Resin and the 1 or 2 pieces that were normal GW plastic it worked, even from the same batch of mixed putty.  So it appears something reacts and stops the mould setting when it's touched Resin, does not matter if you remove the item successfully and leave the mould to dry for days, it will never set.

 

Here's a picture of 2 moulds from the same batch, the one of the left I was able to leave impressions on it 2 days later using a clay shaper with the slightest pressure.

 

To try and get round this I applied a thin coast of Lahmian Medium to the 3D Resin bit and took another mould and this time, no issues.

 

So has anyone else experienced this and if not use this as a warning if you like making moulds.

Edited June 26 by sbarnby71
grammer

[Evil Eye]

Platinum-cure silicone absolutely hates 3D resin. What you need is tin-cure, which is cheaper and borderline immune to curing inhibition. The only downside is it isn't a 1:1 mixing ratio, you have the rubber itself and a hardener which is mixed by weight.