[ATM] Ultra Thin slumped mirrors

[vorblesnak@peak.org]

Having finished, the original 16 inch by 1/4 inch thick mirror,  I sent it
back to Mel.  He may coat it and mount it, or??  It was very short, an
F3.5, with quite a bit of curve to the slump.  I did get some viewing out
of it in a crude truss scope.  The simple soft point cell for the mirror
worked quite well,  I sent it back with the mirror.  The figure was pretty
good, a bit flat yet, and a 1/4 inch turned edge.  I have yet to do a
mirror without a turned edge.  I think I work too fast.

I feel the next test should be on a 16 inch with a shallower slump, say an
F5 or F6.  The question being how the depth of the curve affects the
strength of the glass.  The meniscus shape added quite a bit of strength
to the very thin glass.  In fact, I used a 1 inch thickness when I used
PLOP to design the cell.  This was based on the measurement from the edge
of the glass to the table top it sat on when I measured it.  An F6 would
have less curve and so should react as a much thinner mirror.  My gut
reaction is,  it will be as strong as the shorter focus one was.

I have acquired a piece of 1/4 inch plate, cut to a 16 inch diameter.  I
cannot find a kiln that will slump it for me.  I am on the verge of
building my own kiln but I thought I would check here on the list.  Does
anyone know of a kiln, capable of slumping at least this piece.  I hope to
next try a 24 inch  by 3/8ths inch thick once I have worked this 16 inch
up,  so they may get another job in a few months.

David Davis
Toledo, OR  97391

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