Silicone/Alginate compatibility problem?

Hi all,

I've brushed a print layer of silicone (3481 RTV) on to a lump of alginate and the highest points of the lump don't seem to be curing properly - the silicone is still tacky to the touch and will sometimes actually come away from the alginate. I suspect that this is because of the water content of the alginate but I may be wrong. I don't seem to ahve this problem with alginate that's been allowed to sit in the open/in a cloth for a few hours.

Does anyone know if water would inhibit silicone in this way?

May I ask, why you´re applying silicone over aligante (which is a mold-making compound by itself)?

But yes, even silicone is moisture sensitiv. You have to wait for the alginate to dry completely.

Sure you can ask. I'm making sculptures that'll be eventually cast in tinted clear resin with embedded light sources. They're made by containing alginate in cling film, then shoving as much as I can manage into my mouth and then reading texts out loud into them. They come out a bulbous, organic, organ-like things. I'm trying to capture the shape before the alginate dries out and shrinks. The image below will give you an idea:



It's had 2 print layers on it in the image. 2 thickened layers are added after.

I'll be de-moulding this tomorrow so I'll have an idea of whether the process works or not. I'f not I could try taking a plaster cast of the alginate form and then creating a silicone mould off of that but that's something I'm not completely sure how to do yet.

Might be a stupid question, but did you use the catalyst in the silicone? As far as I can tell the 3481 comes with a pink catalyst that you'll need to mix into the base in order for it to cure.