Moldmaking Help Please

holtzy

New Member
Sorry to bored you guys with questions from a newbie, but...

I am looking to start doing some castings and I am a bit overwhelmed by all the different products on the market. The project that I want to start with for practice is to make a food grade silicone duplicate of a glass cup. I would like to make one that has a frosted look to it and another one that is as clear as glass as possible.

Can anyone suggest what products I should use for a reusable mold and what should be used for the casting. I would like go with a product from Smooth-On if possible because I have a distributor right here in town. I also would like to keep it cheap if possible.

Any advise is on this would be appreciated!
 
I'm not familiar with any "food grade" casting silicones or resins.I'd contact Smooth-On and ask them for product referral and advice.However,if you were only making a mold and casting for practice and experience(not intending on using it for food/drink purposes),there are a couple of silicone mold building/casting RTV rubbers to choose from.I'm not sure where you are.Are you in the states or abroad?Smooth-On has a good selection,and they have a standard *work horse* RTV silicones.As for casting something crystal clear,there are only a few casting resins I know of.Poyester resin shrinks a great deal.You add a catylist to cause the resin to cure.It is also very strong smelling,so a well ventilated area is an absoloute must(always use eye/hand protection).It also could crack/fracture in the mold if too much catylist is added and it generates too much heat.Smooth-On has a water clear urethane resin(I forget the name),and there are a few to choose from.One is made for thin wall castings,others are for larger castings and (because I don't remember) require to be cured in an oven. There is only one way I can think of to create a *frosted* look and that is glass beading the surface.Passche has an "air earaser/etcher" just for this purpose,other than that...I'm not sure?I suppose also you could "wet sand" the surface as a cheaper alternative,but I don't think it will produce the same look,just remove the gloss surface. The one thing about silicone RTV is that it is NOT CHEAP.I don't know of any cheap mold making silicone rubber and resins can be pricey too.Especially the "water clear" urethanes,but polyester is relatively cheap.I suppose that depends how you define cheap?Just F.Y.I.Maybe someone else has some good ideas/advice?
 
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Smooth-Sil 940 is recommended for food-grade uses. That is a silicone rubber you would use to make molds to pour into, etc.

Task 15 is suitable for dry food ONLY uses. Even it wouldn't be ideal for a cup (that you'd probably drink out of).

Frankly, mixed resins are a petroleum product, and as such, do not fall into the guidelines the FDA approves for any use with wet food products. And the chemicals that go into the clear resins are even less suitable. If you're looking for education on how to make detailed replicas, we can help, but you're not going to want to have actual food use in mind as the end product.
 
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