Plaster + Borax?

Discussion in 'Investment casting Block method' started by JBC, May 18, 2022.

  1. JBC

    JBC Copper

    I could have sworn I read in these forums how adding borax into your investment can make your it stronger.
    I can't find it now :(

    I'm wanting to make a 2-part mold using plaster. I have Ultra-Vest but the mold I need to make will be larger than my small burn-out kiln.
    I don't need to use plaster but I'd like the investment not to crack when I pour in the Zamak so here I am.
    Any 2-part mold makers have a history of success with Lowes/Home Depot stuff? Or maybe with Ultr-Vest when not fired?
  2. measuretwice

    measuretwice Copper

    I know its an older post, but for posterity, here's my experience trying it, which in a nutshell was a fail.

    I've been having an issue with Ultra-vest and Plasticast cracking with resin patterns. I too read somewhere about adding borax for strength. Using plasticast, I added 1% of the weight of investment of borax. It turned that easy to pour pancake mix into thick mortar. So thick it didn't really vacuum and was too thick to pour. Racing the clock I added water (was initially at a 39:100 ratio) until I could pour it....then 2 hours later it hadn't set :(

    That was with plasticat. I didn't try ultravest, not wanting to waste more of the stuff. I'm not sure how those who suggest it were able to get it to work

Share This Page