[Jewelry making - Article 00801] - Re: [Orchid] Castaldo VLT Blue Silicone life expectancy

[Peter W . Rowe]

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>     Most low temp and RTV molds deteriorate fairly quickly almost
>     unethically if you know what I mean and I'm sure you do!! 

    "Unethically" seems undeserved. materials are what they are. Use
    them knowing this and all is as expected. 

    For the record, I've got standard vulcanized molds made from Castaldo
    yellow label rubber over 30 years ago which, though they're slightly
    stiffer than they were when newly made, are still quite servicable.
    I've also got some RTV poured Silicone molds made from GE silastic E
    rubber, made perhaps 25 years ago, which have become too stiff and
    crumbly/cracky to work at all any more. So at least this material
    (which may not be as good as current silicone rubbers) does appear to
    have less permenance than standard vulcanized rubbers. But those
    molds were still usable up to fifteen years after they were made, and
    maybe longer. That's not all that bad, in the end, especially since
    those particular molds were being used to inject higher temperature
    carving wax, not the typical lower temperature injection waxes... My
    more recent silicone rubber molds, most made with vulcanized
    silicones rather than the RTV versions (though there are a few of the
    poured ones too), go back at least fifteen years, and even the
    earliest of them, made in the late 80s from a red silicone from
    Contenti, are mostly still just fine. None of them have been used for
    high volumes of injections, so they've not been subjected to high
    usage, but simple time hasn't seemed all that damaging to them. I
    don't consider these to have deteriorated all that much, never mind
    any version of "quickly". 

cheers
Peter Rowe
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