Re: [ATM] Fused or slumped

[vorblesnak@peak.org]

Actually,  only the pie plate gave me astigmatism and only after I had
filled it full of plaster to stiffen it.  Never fill the pie plate with
plaster.  It pulls in odd ways as it cures.  In a few days it comes out. 
This is good, but the polishing you did while the glass was pulled is bad,
very bad.  I have never fixed that plate hoping someday to learn how to
correct astigmatism.

> Try working your slumped thin glass with a full size pitch lap, mirror
on top.   When doing this, touch the mirror only at the center.   You
may want

I ground and polished the 16 inch blank, mirror on top, center over
center.  I polished it to a sphere using a 12" lap left over from an
earlier project.  I am figuring it using a 6 inch lap from another
project.  The figuring is being done mirror on the bottom strokes in 70%
zone, mostly.  I had made a stiffener out of plaster but could not find
it.  OK, so my shop is a mess!  However the ceramic is nearly the same
curve, 21 inch f4, and with a piece of non skid rubber shelf mat in the
curve it makes a great backer to figure on.  I hope to have the 16 figured
by Sunday and will post some pics when I get it done.

David Davis
Toledo, OR

>
> What you are attempting is way beyond my capabilities.   Perhaps your
next mirror will be a sheet of saran wrap?

Hmmmm,  whadaya think Mel?

>
> ... Richard
>
> ----- Original Message -----
> From: <vorblesnak@peak.org>
> To: <atm@atmlist.net>
> Sent: Thursday, February 17, 2005 10:04 AM
> 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
>>
>> _______________________________________________
>> ATM mailing list http://www.atmlist.net/
>
>




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