Craft & Design
Using “Plastex” for molding?

PlastexA Make reader is wondering about using “Plastex” – “Have you heard of ‘Plastex’? I’m interested in the home casting materials of plastex and friendly plastic – the former, in particular, anecdotally seems like it make have enough structural integrity to actually make useful items from and not just use it for gap-filling repair work as it is sold, yet seems much easier to work with than the entry-bar for other types of molding. I have not experimented with these items on my ‘to do’ list. (actually I did use friendly plastic as a kid – it melts however at high temperatures which could be a liability).” Have any Makers out there used this stuff? I’ve only see it here and here.

10 thoughts on “Using “Plastex” for molding?

  1. Lots of hobbyists, model makers, architects and special effects folks use various silicone, room-temperature vulcanizing, etc. casting technologies.

    There are a few different technologies on the market, and they all work.

    Using the stuff isn’t super hard, but there are a few little tricks, like making a break-away mould, getting the parting line right so you can remove your item after casting, getting the surface detail to show, etc.

    There’s a good video (I’ve watched it a few times) called
    “Reproduce Almost Anything” with Ben Ridge.

    You can buy it at, or you can rent it from
    Technical Video Rental.


    (Note: I am affiliated with TVR).

  2. Alumilite really doesn’t work too well and will prove to be quite frustrating for the beginning user. I found in my experiences with it that it tends to not mix well enough to produce a consistent casting. The stuff that I found to work the best were the various Smooth-On products, especially C-1508. Smooth-on also makes a number of molding silicones, some of which have amazing tear strengths and high detail replication.

    To achieve a high caliber casting it’s also necessary that you use a pressure pot to insure a gap-free end product.

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