Silicone molding

The molding clay stop in place with the register dents.
The resulting silicone cast. See where the silicone cast is separating from the last at heel and toe?

I’ve got the first batch of silicone on my last and here are my observations.

First is that I shouldn’t put off until another day the continuation of the project.

Second is that I should put on a lot more silicone in the first coat.  I can work with what I’ve got, I just think it would have been better to keep at it.  When mixed 1:1:1, the combination is spreadable and sets up to the point additional layers could be added in under 2 hours.

Third, I should have used plaster instead of molding clay to build up the ankle and toe of my test last shape.  The silicone and molding clay separate beautifully . . . . but a little too eagerly.  Where the plaster will absorb the water the silicone puts off as it cures, the molding clay cannot and this creates hydraulic pressure which separates the silicone from the clay.  Despite that, I think I can work with this.  It’s just a test and the important bit is neither the top of the ankle OR the toe.  I’ll coat the silicone with a couple layers of mold release and then add the remaining layers of silicone.  I may have to pin the bits that are separating, but I don’t see that as a game changer.

3 thoughts on “Silicone molding

  1. Hi Nori,

    Thank you so much for this blog.

    I also have odd sized, extra wide mis-matched feet.

    Left 9 6E
    Right 9.5 5E

    I’m sad that your Last Making posts have stopped.

    Is this the last we will read about your Lasts?

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