Bubbly bolster

The wheel plan for 622 requires perfect castings. Unfortunately, every attempt so far using my test molds has resulted in large bubbles. These bubbles are not there when I pour the resin, but seem to be forming during the curing process. According to the Smooth-on website, this could be due to humidity, and I should choose a faster-curing resin. I went with their 310, which has a fifteen minute pot life, but perhaps I should have gone shorter. Sadly, I won’t get to the shop to try another product this Saturday, so I guess I have another week of experiments ahead of me.

2 thoughts on “Bubbly bolster

  1. Rene,
    Do you have a vent for air to escape the mold? I’ve found if I don’t include a vent in mold, these air bubbles pop up even with open faced molds. Another way to avoid bubbles is to cast under pressure (but this requires the RTV to be vacuumed or cured under pressure).

    Looking at your picture it looks like you have a bubble in the middle of the casting and on the end. If you are willing to cut into the RTV mold, cut a small (1/16″ or so wide) vent from the end of the mold to the open part of the casting.

    I don’t know if you are on Facebook, but there is a good modeler mold making group available that probably could help walk you through your problems.
    Facebook group is “Mold Making for Modelers”


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