[Jewelry making - Article 00884] - Re: [Orchid] Castaldo VLT Blue Silicone life expectancy

[Daniel Grandi]

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    In reference to Castaldo's VLT rubber and Silicone rubber expectancy
    in general as well as organic rubbers and their uses... 

    Any heat cured rubber, which means all of Castaldo's vulcanized
    rubbers including VLT as well as Contenti's Red Silicone are all
    extremely long lasting and excellent for production purposes. Since
    I have a factory with the ability to run some 10,000 pcs per day, I
    can state with certainty that these are the best, longest lasting
    rubbers for production and are also just as good for small volume
    /small quantities. The Organic rubbers like Castaldo Gold label (
    not silicone based) have the best tear strength resistance of all the
    various types of rubber. That tear strength and elasticity becomes
    very important when making extremely complex molds that have spiral
    plugs and areas that really need to be tugged on when being removed
    from a complex wax pattern. To use this rubber to it's fullest
    extent in those types of molds requires a very good mold maker with
    lots of experience. This rubber can be used for less complex items,
    but it is not neccessary in those cases. 

    Castaldo VLT and other heat cured silicones: 

    The Castaldo VLT is a really good very low shrinkage rubber... It is
    important in all low temp rubbers to make sure that your vulcanizers
    are properly calibrated and that you follow the instructions. (
    calibrated vulcanizers are important for every type of rubber) VLT,
    as with all heat cured silicones are very easy to cut, Knife blades
    last longer when compared to cutting Organic rubber. Wax does not
    stick to silicone rubber. Powder is used to release the air through
    the hand cut vents in the mold. That is the primary purpose of the
    powder... this does a far better job than any liquid release. Liquid
    releases might give a great shine to a wax, but it is actually not an
    air release agent... it will tend to seal the air in and this could
    cause minor areas to not fill as well as they should. 

    Silicone rubbers don't have as much tear strength as organic rubber,
    however, in 95% of all applications, Silicone rubber will be more
    than adequate. The wax will release from the mold more easily, making
    the tear strength not as important a factor in most molds that are
    made. The molds are easier to cut and vent, and can easily be powder
    seperated instead of hand cut. Production is and can be greatly
    increased in most cases by using Silicone molds... Mostly because the
    wax releases so easily if the mold is correctly made. We prefer using
    heat cured silicone molds for 95% of the molds we make because they
    don't dry out and they last for a very long time. How Long? I was the
    original developer of heat cured silicone molds for the Jewelry
    industry about 30 years ago while I was working for a jewelry supply
    company as a lost wax engineer designing jewelry machinery, materials
    and supplies. I still have the very first test molds from back then
    and I still make a few products with those molds.... How many
    pieces... how about over a million wax injections from 1 set of molds
    ( a set being 10 molds of the same piece so we can handle the
    volume). 

    I also have some castaldo gold label molds I made 40 years ago and
    those work also... 

    Most of the Silicone we use is Castaldos VLT for low shrink
    applications and Contenti supply's Moldex red Silicone which has a
    higher shrinkage and makes a slightly stiffer mold. 

    Castaldo has many other types of Silicone mold rubbers for many
    differrent applications. Consult Castaldo's website for applications. 


    There are other rubber manufacturers and other types of rubber other
    than Organic and silicone. I have not gone into any detail about
    those due to the fact that I have to get back to running my
    business. 

    I will say that you can use 2 part poured rubbers of which some are
    silicone based. these are good for copying wax models and some
    organic materials. They have their particular uses, But by and large
    are not commonly used for production by any major manufacturers. 

Hope this is helpful,
Daniel Grandi
Racecar Jewelry Co. Inc.

We do all forms of model making, casting and finishing for people in the 
trade in a wide assortment  of materials and metals. Contact: 
racecarjewelry.com 
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