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/diy/ - Do It Yourself

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2049432 No.2049432 [Reply] [Original]

I'm not sure if this is even the right board to ask but I recently wanted to make some molds and casts but the way sites lay their products out makes this some of the most confusing shit that I've ever encountered. What exactly is the difference between a rubber used for molding and one used for casting? For example Smooth-On sells tin cure rubber molds that are opaque and transparent. Lets say that I want to make something transparent. Why could I not use one of their opaque molds to make a mold of the object and then use one of their transparent molds to cast the object? Wouldn't you just have to apply a release agent to make sure they don't stick? Like why would I have to buy one of their clear urethane casting rubbers?

>> No.2049447

>>2049432
>What exactly is the difference between a rubber used for molding and one used for casting?
The short answer : not much
The longer answer : you want different properties for the material a mold is made from then what your casting is made from. And you don't want your casting to even possibility stick to your mold. Mold-release isn't some magical "never stick to me" product. It's more of a strong suggestion that helps the normal non-sticking.

You haven't said what you are planning on making so we can't help you with the materials used for that application.

>> No.2049456

>>2049447
So basically rubbers made for molds will just adhere to each other?
>You haven't said what you are planning on making so we can't help you with the materials used for that application.
I just got a 3d resin printer with a large build plate so I was just planning on making some molds and then casting with a clear rubber.

>> No.2049468

>>2049456
>So basically rubbers made for molds will just adhere to each other?
Roughly. Think of it as chemical compatibility.

>I just got a 3d resin printer with a large build plate so I was just planning on making some molds and then casting with a clear rubber.
That's actually a really cool idea. Most of the time people cast resin in a rubber mold, not rubber in a resin mold. One thing you could think of is printing a "master", making a rubber mold from that, then casting resin in that rubber mold.

One possible source of confusion is that "rubber" and "resin" are terms used for many different substances.

>> No.2049473

>>2049468
https://www.smooth-on.com/products/clear-flex-30/#
The video on the page is the kind of shit I want to make. That clear urethane stuff is expensive as fuck though. It's $200 for a gallon and it also says its shelf life isn't that long.