plaster molds

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

Thank you very much in advance.

Jan

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




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

Thank you very much in advance.

Jan

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

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.

--
Connie Ryman
Cryman Studio

wrote in message
oups.com...
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

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

On 25 Dec 2004 09:55:38 -0800, (Zenka) wrote:

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

Thank you very much in advance.

Jan

Marcia wrote:
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


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

On Thu, 16 Aug 2007 08:47:53 +0300, Lauri Levanto
wrote:
Its not the dust thats the problem but what it contains. silica is
very hazardous whereas refractories containing calcined clay are not
so.
Marcia wrote:
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


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