Re: [ATM] Source for Dental Stone

["Lawrence Sayre" <lsayre@neo.rr.com>]

On Sun, 11 Apr 2004 12:35:07 -0400, Donald "Don" Ware <mimas@charter.net>  
wrote:

>
> ----- Original Message -----
> From: "Robert Turner" <rbturner@charter.net>
> To: "ATMList Post" <atm@atmlist.net>
> Sent: Sunday, April 11, 2004 10:37 AM
> Subject: [ATM] Source for Dental Stone
>
>
>> Where is a good cheap source to acquire dental stone or plaster good for
>> making tile tools?>
>
> My dentist's supplier was unwilling to sell directly to me, so I just
> ordered a 25# box through the dentist.  Cost about $10 as I recall.
>

A rep at U.S. Gypsum Co. directed me to a local mould/casting based statue  
maker (nothing too fancy, just the crazy kinds of things that people place  
in their front yards, including lowly bird baths and the like).  This guy  
buys loads of Hydrostone and Tuf Stone from U.S. Gypsum.  I bought a 100  
lb. bag of Tuf Stone off of him for $35.  If I had to do it all over  
again, I would just take the Hydrostone instead.  Per the U.S. Gypsum rep,  
Tuf Stone is just Hydrostone with fiberglass strands added to make it even  
a bit tougher.  I found the fiberglas strands (there are lots of them to  
say the least) to be a big nuisance.  Either one sets up with far more  
tensile strength and overall water resistance than any of the Dental Stone  
varieties that U.S. Gypsum supplies to dentists (these all being  
off-shoots from the U.S. Gypsum Hydrocal line of "pour stones", per the  
rep).  I never once externally treated a Tuf Stone tool with anything to  
make it more water resistant, as I never had to.  Soak it in warm water  
(for hot pressing), wash it, etc, ... with no problems.

As it stands now, I work for a company that makes automobile body filler,  
so I've been working a 30" mirror (just polished out) with 100%  
lightweight auto body filler tools.  The body filler I'm using has had a  
special hardening inhibitor added, so it sets up in ~12-15 min., instead  
of the typical ~3-4 minutes of regular auto body filler off the shelf, and  
this makes it a bit easier to mix, pour, and spread out evenly in the tool  
mould (Formica works great here, as body filler won't stick to it) before  
it sets up.  One big plus is that lightweight auto body filler tools weigh  
roughly ~50% of Hydrostone tools with the same dimensions.  Heavyweight  
body filler would fall somewhere in-between these two weight extremes, or  
perhaps be closer overall to Hydrostone in final weight.  Another big plus  
I've found is that body filler is far less likely to scratch glass than  
"pour stone".  The only drawback I've experienced with body filler vs.  
pour stone, is that body filler has a "much higher" shrink rate, and this  
means a bit more work making full contact, as you have to work the  
resulting curve difference between the tool and the mirror away first.   
Heavyweight body fillers shrink much less than lightweights, or so I've  
been told.  The main disadvantages to people buying body filler at the  
store would be that the cost is quite prohibitive (an understatement) vs.  
pour stone, and the 3-4 minutes to hard once the hardening agent is added  
problem is a killer to overcome.

Lawrence Sayre
-- 
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My philosophy, in essence, is the concept of man as
a moral being, with his own happiness as the moral
purpose of his life, with productive achievement as
his noblest activity, and reason as his only absolute.

Ayn Rand (in the appendix to 'Atlas Shrugged')
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