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Plastic Resin Casting and Molding advice

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  • Plastic Resin Casting and Molding advice


    I'm making my first plastic resin cast and the mold for it using the tutorial. One difference to the tutorial however is that the object I am making a mold of is something I've make in air-dry modelling clay. I've spent quite a bit of time making the original so bit worried about pouring the silicone for the mold onto the clay object - will it break the clay down or is there some way to prepare the clay (varnish or something?). I've put a test of dried clay in water and it has broken down in five minutes. Can anyone who has done this sort of thing before advise please? Thanks in advance.


  • #2
    Is the mould material one you heat up and melt or one you add a hardener to. The latter should be ok. If you are using one you melt you will get loads of bubbles in it with a clay original!/sjcritchley


    • #3
      I use a 2 part moulding putty for things like this - it hardens quite quickly so there's not a lot of working time, but you don't have to worry about damaging your original. This is of pretty high importance to me - I'm still smarting from the time (about 15 years ago!) I poured hot sillicone onto a month's worth of work and watched it melt into a puddle

      Just an idea if you're not totally set on the pouring option!


      • #4
        Hi Brian,

        this is very interesting. I recently started to be interested in making my own molds, because I wanted to have a silicone version of a very nice plastic soap mold that is difficult to unmold soap from (mainly if the recipe has an important part of unsaturated oils - for the record, it is one of the Milky Way Molds).

        So I found this OOMOO30 - Silicone Rubber compound when I was in the US and used it to make a soap mold (I put the how I did it on my blog if anyone interested - cannot post links yet). They say to wait 6 hours before unmolding, which I did.

        I am really not an expert, so my apologies if I do not use the right expressions:

        1) I used some ceramic resin powder to make the master model (is this how you call it?) - the original plastic mold was a bee mold with bees, so had a lot of detail
        2) Upon unmolding the master model, some of the resin sticked to the plastic mold, so some of the details were lost, but not too much (I did not use the easy unmold spray for the plastic mold before casting)
        3) Then I constructed a small wooden frame around my ceramic master model and poured the OOMOO30 compound (2 parts mixed)
        4) I unmolded after 6 hours and already used it twice for soap - it works really perfect!

        I did not use the hairdryer to heat the compound and indeed there were some small bubbles in it, so I will give it a try for next time (not sure to what extent bubbles affect the lifetime, but I think it is important not to have them).

        Also, I am not sure - does the 48 hours you suggest apply also for this compound? I did not have an impression it shrinked after, but I did not measure either...

        Also, I would like to ask - is this compound something that will survive a longterm use? I am planning to make more, so I want to know if it is worthy.

        I have also bought their urethane rubber ReoFlex, but I am a bit worried to use it for soap molds - they say on the package it contains carcinogenic compounds so I wonder if these remain in the final mold? Not sure what to think about it... would you recommend it for soap?

        Thanks for any advice!

        PS: I had a look at your soap molds offer and they look wonderful, do you ship outside UK in Europe?
        Long live your bar of soap!
        My blog:


        • #5

          I am just starting with resin moulding and am waiting for delivery of essentials. After purchasing vinamold re-useable moulding compound, I am wondering which melter to go for. Are there any members who could give me advice? I have been looking at the Lee melter, 150ml which would be just about the right size for jewellery moulds, I think. Any help and advice would be appreciated.