Need casting advice.

Discussion in 'Finishing Techniques' started by derekh, Jan 15, 2010.

  1. derekh
    derekh New Member
    Okay, before I go in depth with this, let me say that the end result I am looking for is my items made in silver, and repeatable. That being said, here is what I need help with.

    For the prototype design, I ordered the model in the white detail material. It has given me some fantastic results as far as resolution and the design came out perfect. I need to make a mold of it. I have access to a guy that makes resin models all day long, cast from silicone molds of his. (Think 40k little model type things and that will be pretty close.)

    So, my first question is, with him having a vacuum chamber and the silicone for molding already, will that work for a mold for a piece of jewelry?

    Second, what kind of wax do I need to use with said mold above to get perfect reproductions to have cast in silver?

    We are going to have to do most of this ourselves, save for the actual silver casting, and neither of us has worked with wax before, so neither of us has any idea of which wax would be best.

    When we make the mold do we need just the sprue or do we need to mold in a vent as well for the wax?

    Thanks, and I look forward to hearing your answers.
  2. derekh
    derekh New Member
    Still needing suggestions here people, I have no idea which kind of wax to get and would rather some kind individual say "Oh, this will work well" rather than me having to buy 30 different kinds and having most of them fail.
  3. locodan
    locodan New Member
    Search for jewerly supply for injection wax. There are several types with slightly different charistics. The main issues with wax is how it flows when heated and that it will burn out completly with no ash at max flask temperature of 1350 deg. F.

    RTV will work fine but you have not addressed the issue of how you plan to get the wax into the mold. This is usually done with a heated pressure pot. A sprue is added with a conical end that matches the push to open valve on the wax pot;.

    Vents are normally not used for injecting rubber molds. For simple objects the mold parting line allows for the air to escape. With more complex forms a test run is made and where there is incomplete filling small cuts are made in the rubber to work as a vent. This weakens the mold so do not make the relief cuts deeper than nessary.

    There are several good books that give detailed explainations of the whole process. The one I used to learn lost wax casting and rubber molds is "Centrifugal or Lost Wax Casting" by Murry Bovin.