Styrene plastic as a mold for casting resin?

Tools, Techniques, and Reference Materials Techniques
1

I have a fuselage with some raised details that I want to make a hard resin impression of. If I make a little barrier around the detail, can casting resin be poured directly on the styrene and be separated after it cures?

2

Not easily. Perhaps if you slather on enough mold release the resin won’t stick to the plastic. The liquid resin which has been in contact with plastic sheet tends to stick very well. I use resin poured into a styrene form to scratchbuild solid ship hulls. The resin doesn’t separate easily.

You may also break your master when you’re trying to flex the part out of the solid resin casting

Casting resin generates heat as it sets. Too much heat can (and will) warp the plastic master part.

What are you trying to do, make a negative of the positive which can he used as a buck for vacuforming?

I think the procedure might be to make a RTV negative of the positive. Apply mold release to the RTV negative and make a RTV positive of the negative, then cast your resin negative from the second generation RTV positive

3

Thanks Ed. I have burnished lead foil over small scoops on the side a fuselage before with success but the one on the side of my Albatros are a squarish shape and it’s not working as well. i wanted to try to burnish the lead foil “into” a negative mold instead over “over” part. I think making the rtv mold then and rtv positive, as you suggested, is the way to go. Was wondering if I could save the step but have come to far to “F” it up now…and still plenty of opportunities to still do that[:S]

4

If you have RTV casting stuff anfd the casting ‘FU’, then do as suggested above.

I’ve had some (small) successes slathering the part in vaseline or similar, then (smash-casting?) pressing into a pre-prepped blob of Plasticene, Silly putty, bathroom sillicone, etc, then allowing the negative impresion to cure.

Pour resin or plaster into the negative to make a positive. This may obviate the need to use foil to duplicate parts.

5

One of the best ways I’ve found to make casting boxes is to use LEGOS. This allows you to make a custom shaped box which can be disassembled once the RTV has cured eliminating potential damage by trying to removed the casting from a rigid container.

6

I have fears that straight vaseline may obscure fine detail, so I mix vaseline 1:1 with paint thinner/turpentine to make a mold release. Makes it much thinner and it still is a good mold release.