Re: [ATM] polish time for 13 inch

["Bob May" <rmay@nethere.com>]

Mitch, the thing here is that the mirror isn't left standing  but
is rather moved around the lap so that the entire surface tqkes
on the shape of the surface of the mirror.  You can't stop and
let things rest on an oversized lap otherwise the lap will
depress where the mirror sits.
As long as the lap exibits a decent contact with the glass, you
can do rough polishing without any problems.  The problems
happpen when one side of the lap drops and you end up having a
hill in the middle that the mirror falls to one side or the
other.  This is part of the reason why many don't like wood for a
backing for the lap.  Wood tends to move more one way than in the
orthanognal direction, i.e. the widthwise direction moves more
than the lengthwise or grain direction.  Also, wood tends to warp
with a hill generated along the grain direction.  Pressed wood
products don't exibit this problem so they are usually used and
often not mentioned as such for the type of wood mentioned.  The
pressed wood tho, does exibit some problems if water gets very
far  into the product so be careful there.  I prefer non-grained
products like stpoured stone, plastics like Corian or other
imitation marble type stuff for the kitchen countertops and
metals.  They don't move.  Thickness can be a problem tho as thin
stuff will bend under the pressure and that will deform the lap
and cause neverending problmms that you often can't figure out.
Bob May
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