Re: [ATM] composite mirrors and epoxy handling hazards

["Peter C Chen" <peterchenmd@comcast.net>]

Mr. Lindner:

                    The type of mold release depends on the specifc epoxy
system used, and everyone I know has his/her own favorite formula.   I have
heard of hair spray, WD-40, candle wax, mineral oil, KY Jelly, etc., being
used.   If you use the Star Technology ER2109 epoxy sytstem
 http://www.star-technology.com/table1.html
that I suggested in my Stellafane talk, the appropriate mold release is
Johnson's Furniture Paste Wax.   The idea is not original.  I owe it to Donn
Starkey who owns the company and is also an avid atm.   I have also used
Freeman wax with some success.
http://www.freemansupply.com/FreemanWaxRelease.htm

                     Be sure you have done some experiments and have gained
some experience on disposable molds before you do the serious casting.
Also, be aware that a new mold will have a tendency to stick. Two pieces of
16" glass blanks epoxied together, as once has happened to me, is not a
pretty sight.  (Reminds me of a memorable episode in Jerome K. Jerome's book
'Three Men in a Boat'.  Does anyone still read that?).   One solution to the
problem is to condition the mold with polyvinyl alcohol (PVA).   The
procedure is described in
http://winshipmodels.tripod.com/pva_mold_release.htm

                  For vacuum bagging procedure, see
http://composite.about.com/library/weekly/aa000109.htm

                    Finally, the key to getting a good optical figure, as
you have astutely observed,  is to have an exactly even coating of mold
release. This can be done by careful polishing and watching the interference
fringes between the glass and the wax.   It is a tricky business which I
cannot claim to have completely mastered.  On the other hand, I am sure
there are many atms who are true craftsmen (craftsperson? craftspeople?
craftshumankind?) for whom it will be a snap.

Have fun.

P. C. Chen

----- Original Message ----- 
From: "Michael Lindner" <mikell@optonline.net>
To: "Peter C Chen" <peterchenmd@comcast.net>; <atm@atmlist.net>
Sent: Friday, September 24, 2004 10:04 PM
Subject: Re: [ATM] composite mirrors and epoxy handling hazards


> Mr. Chen,
>
> Thanks for sharing your expertise with our list. I wish I had been at
> Stellafane this year to hear your talk. Regarding mold releases, can you
> recommend any which you have successfully used to make a replica mirror? I
> would think that's the most difficult part, as an uneven release layer
would
> destroy the figure.
>
> Clear skies.
> -- 
> Michael Lindner
> http://www.starastronomy.org *** http://home.att.net/~mikel
> http://www.atmsite.org *** http://www.atmlist.net
>

_______________________________________________
ATM mailing list http://www.atmlist.net/