Re: [ATM] start...tool....

[Charles Mitchard <charlesmitchard@iinet.net.au>]

I would second all of Vladimir's statements.
The main difference between the different dental stones is its expansion 
factor upon setting.
all the tubs I've purchased (in Australia) have information such as:-
Physical Properties
water.powder ratio :- 33-35 parts water to 100 parts powder by weight
comprehensive strength at 1 hour - 3920 psi
initial set 7 - 12 minutes
Linear expansion on setting at 2 hours - 0.16%
this is for yellow stone extra hard.
The Buff die stone has an extremely low expansion factor.
Again these colours are for australian dental stone from Ainsworth Dental 
co pty ltd
One word of warning ---- dont try to speed up drying in a micro wave oven, 
the item will craze and often split. a standard oven at 90'C works well 
though. Well that was more than one word but you get the gist.
Regards
Charles

>Dental stone comes in different colors, my last was deep blue.
>So color is not criterion for identifying it.
>Important characteristic of dental stone is that it should
>not be water soluble (after curing). If there is any possibility
>  to check on this, do it.
>Once I was investigating with dentist supplier about dental
>stone. They admitted that they are not able to tell anything
>about its water solubility, instead they offer me a free demo
>package with several colors for me to check.  I am telling this
>to warn about existence of demo samples, and if suppliers are
>contacted they may be questioned  also for offering free demo samples.
>
>Dental stone is sort of "hi-tech" of present, but many mirrors were
>ground in past with plaster of Paris or cement tools with success.
>If you have chance to get hands on dental stone try it, but do not
>despair if it is not readily available. It is not essential.
>
>Regards
>Vladimir.
>
>
>
>
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