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

[Mark Holm <mdholm@telerama.com>]

Vladimir Galogaza wrote:

> Dental stone comes in different colors, my last was deep blue.
> So color is not criterion for identifying it.

My little bit of web research agrees that color is not standardized
among different grades of dental stone and dental plaster.  I think I
saw the same grade available in different colors from at least one
manufacturer.

Here is a link to the Dental Stone and Dental plaster products made by
the Kerr company of the United States.
http://www.kerrlab.com/laboratory/products/stones/index.cfm

Probably the Vel-Mix product is the most favorable for atm tool use,
combining low shrinkage/expansion with high strength.  Very likely, any
of the stone products would work, from a physical properties standpoint.
   Water resistance is not listed.  I know at least one atm has used and
recommended Vel-Mix.

Note the very much lower strength of the dental plaster products.  The
strongest plaster product has only 8% of the strength of the weakest
stone product.

Note also that the Vel-Mix is referred to as die stone.  This apparently
indicates suitability for a particular type of dental lab task, and may
be used to describe similar products from other manufacturers.

I would avoid rapid setting products.  The stuff I have used (brand
unknown to me) was plenty fast.  If anything, it bordered on being too fast.

Also take a look at these "Industrial" plasters and gypsum cements by
USG.  I know that atm's have used Hydro-Stone successfully.  Tuf Stone
also looks a good bet.

http://gypsumsolutions.com/search_details_lit.asp?DocId=580

Quote from above link:

HYDRO-STONE® Gypsum Cement—hard and
strong, especially suitable where high strength
and resistance to water absorption are necessary.
Cannot be worked under a template. Used in
high-quality art novelty and statuary castings.
Should not be cast in glue molds, but works well
in plaster and other flexible moulding compounds.
Expands about three times greater than
HYDROCAL A-11 or B-11 Gypsum Cements.
TUF STONE™ Gypsum Cement—polymer-modified,
fibered casting material formulated for solid
cast giftware applications.
3-D Casting and Statuary

The setting expansion for Hydro-Stone and Tuf Stone is higher than for
the die stone products, but I know atm's have used Hydro-Stone.

Products similar to these may be widely available.  Gypsum cements are
not particularly high tech, or particularly expensive.

Mark Holm
mdholm@telerama.com

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