Re: [ATM] A polishing we will go!

[Mark Holm <mdholm@telerama.com>]

edwski@comcast.net wrote:

>back to polishing.  All was great until I heard the most dreaded sound you
>can hear while grinding/polishing. @$%&* I had scratched the blank!!. There
>are a few, one or two that I don't think will get polished out. The pitch
>lap was made on a base of some-sort of poured material, this is ok, but
>there were still tiles from grinding under the pitch. GRRRRR. I was back
>again this past friday, we switched to another pitch lap, this one is better


One of the secrets carefully guarded by the keepers of dental stone tool
knowledge is that you can make a dental stone lap backer even easier
than you can make a dental stone - tile tool.  Both jobs are quite easy
and fast.  The really impatient claim to be able to go from raw
materials to a working tool in under an hour. (Actually, I seem to
recall that Bob May claims under 1/2 hour).  For a pitch lap base, you
need to allow time for the thing to dry out so pitch will stick, and you
don't want to force it too much with an oven.  Heat isn't good for
gypsum based products.  So, the obvious time to make your lap backer is
when you make your tool.  You have all the materials and equipment ready
to go.  Since you have no tile to deal with, the lap backer takes even
less time.  When it is solid, set it on a thick layer of old cotton
towel, in a place with good air circulation and moderate warmth.  By the
time you are done with fine grinding, the lap backer will probably be
dry enough to pour pitch.


-- 
Mark Holm
mdholm@telerama.com

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