Re: Investing and Bubbles


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Posted by John Dach on March 17, 1999 at 02:34:52:

In Reply to: Re: Investing and Bubbles posted by Jack Davis on March 16, 1999 at 09:21:56:

I do not think there would be enough vacuum from a shop vac to eliminate the bubbles....... it might get a few of the big ones but as far as I know (and do) about 29" of vacuum, enough to get the water in the investment to "boil" so there is an agitated de-gassing. This really removes all of the bubbles (will cause investment to be "sucked into most any cracks, surface bubbles in the wax or other defects) and makes the investment very creamy. For the jewelry, if we don't get the "boiling" effect, there can be bubbles on tha casting. Also, if no vacuum is available, blowing, spraying or splashing (via wetted fingers thrust from a loose fist to extented fingers) investment onto the sprued pieces and then placing the can over the items and filling as normal will eliminate an amazing amount of the surface bubbles. Banging the can as it is filled also will get a good bit of bubble removal. Also, be aware of teh surface tention bubbles vs the capture bubbles, both removable but requiring different processes.

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