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

[John Lynch <john_lynch2006@yahoo.com>]

Before going into too much detail, someone should ask
Saqib what supplies he has available and tailor the
recipe toward that end.  

--- Mark Holm <mdholm@telerama.com> wrote:

> Vladimir Galogaza wrote:
> 
> > There is no doubt that tool made this way will
> work. But amount of epoxy
> > required will probably match the price difference
> between the plaster of
> > Paris
> > and dental stone while dental stone tool will take
> much less time and effort
> > to be fabricated.
> 
> Also some people develop severe allergic reaction to
> epoxies.  The
> Probability is said to increase with exposure, so
> best to save them for
> when you really need them.  Wear rubber gloves too.
> 
> I have done the dental stone method, and I was
> almost giggling with
> surprise when done at how easy and quick it was.  I
> used Richard
> Schwartz's instructions, and they worked like a
> charm.  I think dental
> stone is worth the extra bother to obtain.  As an
> alternative, look for
> a business that casts outdoor statuary.  They might
> be using something
> very similar to dental stone.  I suppose in a Muslim
> country, outdoor
> statuary might be less common.  The same techniques
> and materials are
> used to cast architectural details that look like
> chiseled stone, but
> are less expensive.
> 
> > 
> > Second remarque is about using twice as much
> hardener as recommended. There
> > are
> > some very good chemists on the list capable of
> rectifying me if I am wrong.
> > Epoxy and hardener work together in chemical
> reaction. The reaction is
> > complete and
> > final product is best if interacting parts are
> used in stoihometric amounts
> > which is
> > given by manufacturers recommendation. Surplus of
> epoxy or hardener remains
> > in the
> > final  staff unused (unpolimerized) and weakens
> the whole thing. Surplus
> > hardener does not
> > make final product harder or stronger.
> 
> Just so!
> 
> Probably a confusion with polyester resins, where
> the hardener is a
> catalyst, and using more can result in somewhat
> harder, though more
> brittle, result.  It will also cure faster and get
> hotter.  With
> epoxy-amine systems, the "hardener" is not a
> catalyst, but is the other
> half, or third, or whatever the correct ratio is, of
> the final
> molecules. The ratio given is determined by
> molecular structure and
> going off-ratio does not usually give useful
> improvement in any
> property.  Mix it like the instructions say.
> 
> Mark Holm
> mdholm@telerama.com
> 
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> ATM mailing list http://www.atmlist.net/
> 


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