Frillen wrote:
It may be a stupid question, but if I am mixing 100 g plaster, should I add 20 ml of water or 25 ml?
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Furthermore sprinkling it into the water (4 parts plaster + 1 part water) will make a high island of plaster in the water which doesn't settle automatically, I have to stir the island top into the water which I have always heard is a bad idea!
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Does anyone have experience with stewalin, will it lose its strength if I add more water than suggested?

I have no experience with this specific plaster.

a) However, 4:1 or 4 to 1 or 4 parts plaster - 1 part water all mean 25% water by weight.

b) Stirring the island top into the water being a bad idea -- that's an old caster's tale. It happens all the time. Just mix as usual (which for me means using an electric wand mixer).

c) Everything you do affects the strength of the plaster. The plaster product should come with a Material Safety Data Sheet and a Technical Data Sheet. The first describes how to use the product safely, the second describes the plaster's composition and how to mix it to get optimum strength. However you are mixing it now you won't be getting optimum strength. On the bright side, adding more water won't affect the final cast strength significantly.

By the look of the product I would say that it is designed for slip casting. As such it may have some cement in there. If it does then, IMO, it isn't as suitable for HA casting as other plaster products.

Regards,

Ian P.
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