Re: [ATM] tile tool sticking

["Richard Schwartz" <richard1941@gmail.com>]

Bob May wrote:

"Plaster, dental stone, hydrocal, cement, it's all the same in this regard.
 The stuff is a bit porus and thus will adsorb water until it is full."

This is not right.  The part about absorbing water is correct, but the
difference between dental stone and plaster is like the difference between
your mother's delicious chicken soup and the white stuff from a chicken's
exhaust pipe.   Particularly, plaster of paris will disintegrate when wet.

Bob May wrote:

"Sealing it will stop the adsorption for a little bit but you have
to remember that you have to get down into the stuff in order to
do a real seal and that usually doesn't happen and you'll end up
with patches where the sealing material gets worn away with the
grinding process.  I'd rather not seal and thus get an even
adsorption of the water over  the whole area rather than deal
with spots of non sealed plaster, etc.  This will show up worst
when you are almost done and on the very fine grits where there
will thus be areas where the water goes through and those dry out
and make for problems."

As much as I hate to agree with Bob May, he is right about this.   When
grinding with a dental stone tool, it does not matter if the tool gets
saturated.    For plaster of paris, the use of additives when mixing the
plaster is a subject of future investigation.   One potential additive is
white glue.

For polishing, the tolerances are a lot tighter, and it is best to avoid
water penetration of your pitch lap foundation.   As Bob May teaches,
surface coatings like urethane varnish are worthless.   A much better way to
go is with a penetrating sealer such as Richard's Secret Sealer Sauce,
properly applied and cured.
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