silicone molds and limited success

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This topic contains 9 replies, has 2 voices, and was last updated by  Katherine Swift 2 months, 3 weeks ago.

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  • #23129

    Chris

    Being new to casting I wanted to ask if there are any tips on casting with the larger silicone molds and transparent dyes. the plastic molds work great and produce near perfect results, but when I use the silicone molds (repeatedly) my results aren’t so good. this is under the same conditions when using the plastic mold, the surface bubbles seem to form during the curing process (with silicone molds) as well as inside the piece. Furthermore the bubbles that do rise get trapped on the overhanging top of the mold and ruin it completely I’ve tried release agents warmed resin and warm room temperature with the same bubbling results, while right next to it in a plastic mold my results are near perfect. Can anyone explain why or provide a solution? I would like to use the silicone molds I have but if this persists there useless. Thanks in advance if anyone has had this problem and can provide a solution.

  • #23283

    Katherine Swift
    Keymaster

    Hi Chris,

    I’m sorry to hear you are having problems. Did you make the molds yourself or did your purchase them? Are they made from poured silicone or silicone putty?

  • #23354

    Chris

    I purchased these molds and they are poured silicone not putty, your typical set bought online. A couple of cubes in different sizes, a diamond shape, a sphere. what am I doing wrong with this type of mold? could it (again) be this Chicago weather? Heating the resin and the room I’m molding in solved my problems with the plastic molds with great results, but the silicone molds are not cooperating. Could it be the room temperature not high enough? Being Chicago area I’ve used a space heater and my room temp. is approaching 90 degrees. so I don’t think that’s it. The bubbles appearing well after pouring (internally and on the surface) is what I can’t explain. I’m open to any suggestions. I’m very pleased with R E’s clear resin but it does not want to cooperate with the silicone molds, what am I doing wrong? One last question what temp. is sufficient to warm the resin? Making coffee one morning I emptied a teapot along with hot tap water to warm the resin and the results were excellent, can boiled water be used? and would that solve my issues with silicone molds? I’m at a loss anything beyond this I think needs a pressure pot maybe. thanks for any tips.

    • #23422

      Katherine Swift
      Keymaster

      Hi Chris,

      Thanks for the additional information. It is helpful.

      While your room temperature is warm enough, your molds may still be too cold. Even with warm resin, if there is a significant difference between the warmth of the resin and coolness of the molds, you can still get bubbles. Try heating up the molds in a warm toaster oven (150F) until they feel warm. I’m guessing 10 to 15 minutes or so.

      Heating the water to the point of ‘making tea’ is a good temperature for warming the resin. (That’s what I do.) . Don’t use boiling water as there can be too much of a good thing. If the resin gets too warm, you will shorten your pot life.

      Let me know how this works for you. 🙂

  • #23534

    Susan Sinclair

    Sooo, are you really saying that the 3 flower Large Rose silicon mold is going to turn out perfect, frosting-like roses?

    • #23540

      Katherine Swift
      Keymaster

      Hi Susan,

      I’m not sure I understand your comment. What in particular are you most worried about?

  • #69210

    Janet reed

    Hi, this is the first time this has happened. 2 of my molds bubbled and foamed. They are hard as a or know. None of the others did this. Any ideas?

    • #69449

      Katherine Swift
      Keymaster

      Hi Janet, I’m not clear on what happened. The resin bubbled and foamed or the mold bubbled and foamed?

    • #69867

      Janet reed

      The resin bubbled/foamed up and then became hard/glass like

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