plaster molds

Can anybody tell me, how to reduce cracking of plaster molds.

Thank you very much in advance.

Jan

Reply to
Zenka
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Ahoj Zenka Please give more information: What is your mold mixture? What temperature are you heating the molds to and for how long. Start with answering those questions and perhaps we can help. Jindri

Reply to
Henry Halem

Ahoj Jindrichu,

Mold mixture is plaster:silica 1: 1,5 I am using 720 degrees of Centrigrade for 60 min. Thank you very much for your kind response.

Jan

Reply to
zenka

Hi Jan, there are lots of different mold formulas. The one in my book for plaster/silica is:

1 part No. 1 Pottery plaster to 1 part Silica flour mix dry ingredients together well before adding water use 50 parts water to 100 parts mix use the slow cure method (I'm not sure how slow that is) for large molds add 1 cup chopped fiber to 5 lbs water before adding to mix

Wrap your mold with wire when you go to fuse the glass.

Hope this helps.

Reply to
C Ryman

I was always worried about the health risks of silica flour so used to use Molochite or Sinterlite (calcined clays) But now I am getting exellent results with SRS Ltd.'s "Glass" which is ready mixed. It costs £15.80 for 25kg from Special Plasters in Hockley Birmingham. (not on web i think)

Marcia

Reply to
Marcia

I am afraid you have essentially reduced the health concern, and much less the hazard. With a ready made dry mix you have veru much the same amount of airborne dust while mixing it with water.

-lauri

Reply to
Lauri Levanto

Reply to
Marcia

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