[ATM] Fused or slumped

[vorblesnak@peak.org]

Mostly this is to Jean-Guy, but it has bounced with direct mail so I am
posting it here in hopes he will see it.  That and it is a good question
for everyone to discuss.

Hello Jean-Guy,

I am currently finishing the figure on a 16" by 1/4" thick slumped mirror.
 It is an f3.5, very short.  This is a plate mirror by the way.  I had
wanted to talk with you about what decisions you had made that lead you to
an engineered fused blank, as opposed to a simple slumped blank.

My first mirror was an 18" by 3/4" plate glass mirror.  It had problems
just placing it on the board to work it.  So flexable.  There was a hump
on the back of the mirror and this was sufficient to cause a 'volcano', a
ring with a depression in the middle, on the face.  The 16" by 1/4" has
never given me that trouble.  Warming is an issue.  Just by warming the
back of the mirror with my hands I can correct it perfectly, but only
temporarily.  This makes for an interesting time polishing and figuring.

I believe the difference is in the slump.  The section of a sphere
configuration of the entire blank seems to lend more strength than one
would suspect.  I am considering just slumping a piece of the pyrex plate
and trying a mirror from that.  Still, I told Mark I would work on his
idea a bit.  Mark did a 12" prototype and got a good figure, but had some
print through of the grid configuration from the back.  This is a cast
ceramic blank made of low fire slip.  His next blank, the one I am working
on, had a thicker face but I have not glaze fired it yet to know what will
happen.

Anyway, babbling aside,  why not just slump as opposed to fuse.

David Davis
Toledo, OR

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