Max mold 30

I have access to a dental vacuum mixer. Could I both mix and de-bubble the max mold-30 or would the silicone bubble over and go up the vacuum tube? 
Also, how about long do the molds last? 


  • Chris EllerbyChris Ellerby Los Angeles Admin
    Hi Stephen,

    I'm not familiar with dental vacuum mixers, but when degassing silicone it can expand in volume several times.  If the material bubbling over is a concern I would be careful.

    Smooth-On has a document about vacuum degassing Mold Max 30:

    The life of the mold depends on how it is designed and the nature of the casting.  The more stress you apply to the mold to de-mold your castings, the less life it will have.  Using a release agent can help get more life out of your molds, depending on what materials you will be casting.   If you are concerned about the life of the mold I would make sure to save your master, and also save your first casting so you can make molds of it later if needed.

  • Ok. I was just wondering how long an average mold lasts in general, using a release agent with a minimum of undercuts. Are we talking hours, days, weeks or months? 
  • Chris EllerbyChris Ellerby Los Angeles Admin
    edited April 2020
    How long a mold lasts is not typically measured in time but in the number of pulls (castings).  Good molds can last many years, or a couple of months, depending on the design of the mold, the nature of what you are casting, what material you are casting in, and what release (if any) you use.  There really is no one answer or general rang, it's highly specific to each mold and casting scenario.

    For example, if the shape of the piece you are casting is relatively simple and does not put a lot of stress on the mold when it is demolded, and the material you cast in does not produce a great deal of heat, or the thickness of the casting is not thick enough to result in the material putting out a lot of heat, and you use a release agent, and you are only making a few castings a year, your mold could last for many years.   Change any of those variables and it might only last a few months.

  • I see. So if I make a mold and pour it a couple of days later it should be fine and won’t shrink. I’ll be pouring Dental acrylic. In the video John pours the mold twice for the two colors of acrylic so it looks like the mold can withstand the curing temperatures. I was wondering about the shelf life of a silicone mold. Thank you!
  • Hello,

    I design molds for years and always made metal and plastic injection molds. Now I got a new work about refractory cement mold. It is a material used for fire bricks. Cement will be filled into mold then with vibration, it will reach everywhere.

    I just want to ask that, if anyone has experience with this cement? What material should I prefer for mold? Cement heats up to 80 celcius degree during process and I want my mold to be in good shape and re-use for many. Will styrofoam be fine with 80 celcius degree and chemical affects of cement?
  • ahmedsayeed1982ahmedsayeed1982 Turkey
    edited May 2020 gave the idea
    Post edited by Chris Ellerby on
  • Chris EllerbyChris Ellerby Los Angeles Admin
    I'm not familiar with using refractory cement (mortar) for mold making.  I would be concerned about it capturing surface detail, as the material may be a bit grainy, and how brittle it would be.  It could be fun to experiment with though. 

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