Re: [ATM] Fused or slumped

["Jean-Guy Moreau" <jgmoreau@cablevision.qc.ca>]

Thanks for relaying the message.

Well slumped mirror do certainly work, and they
are indeed very much cheaper and easier to make.
My gut feeling tells me they are also stronger than plan 
parallel ones, but that is a question for the engineers among us,
anyone want to chime in ?

I suggest you keep experimenting, if your example of a 16" x 1/4"
is any indication, this is a very promising avenue to explore,
but why 1/4", it would have been as easy to slump 1/2" glass,
or even 5/8" 

To answer your question, i wanted something as strong as a full
thickness mirror, that would cool fast,
with a flat back that would be easy to figure and mount.


Jean-Guy

P.S. I just went downstairs, and i have a 14" x 5/8" slumped at f/5.7
want it ?



----- Original Message ----- 
From: <vorblesnak@peak.org>
To: <atm@atmlist.net>
Sent: Thursday, February 17, 2005 1:04 PM
Subject: [ATM] Fused or slumped


> 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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