Re: [ATM] convex secondary

[Ken Hunter <atm_ken_hunter@yahoo.com>]

Never saw saucepans that had rims that would mate up
to those on the Pyrex disks... We're talking of even
OLDER Corning disks that had an annular ring around
the backside. They looked like they were done in molds
from Pyrex glass that was "pulled" from a dollop while
in a "taffee like state" , plopped into the mold and
heated just enough to get the topside of the glass
level with the mold top. The top side had rolled
(tensioned) edges, the bottom had the rim. The sides
were tapered.

Ken Hunter


--- "Steven L. Dodds" <steve@pcmw.net> wrote:
> ----- Original Message ----- 
> From: "Joe" <nss@mwt.net>
> To: "Ken Hunter" <atm_ken_hunter@yahoo.com>;
> <atm@atmlist.net>
> Sent: Saturday, March 12, 2005 9:05 PM
> Subject: Re: [ATM] convex secondary
> 
> 
> >I loved those old corning blanks,,  I always
> wondered though  what they 
> >used as a mold?
> >
> > Could handle the temps required and not melt, and
> also have a polished 
> > surface.
> >
> > Joe
> 
> 
> The old Corning blanks with the shiny sides and the
> ridge on the bottom were 
> molded in saucepan molds. Pyrex Sauce pans were made
> by dropping a glob of 
> molten Pyrex in the mold then pressing it with the
> top mold.  Telescope 
> blanks were made by dropping a double glob of Pyrex
> in the bottom mold and 
> letting it sit until cool.  The molten Pyrex without
> pressing would fold 
> over on itself creating creases and voids, hence the
> poor quality.  It is 
> also the reason for the standard blank sizes.  4.25"
> 6" 8" 10" 12.5".. It 
> was the size of saucepans that Corning sold.
> 
> There is your piece of trivia for the day.
> 
> Steve
> 
> 
> 
> Steven L. Dodds
> Nova Optical Systems
> http://www.nova-optical.com
> >
> > Ken Hunter wrote:
> >
> >>In the old days, Pyrex blanks were moulded in
> forms
> >>and were very full of in-homogenities and
> striations
> >>(SP)? These could be easily seen on most any blank
> >>from several y. Lately, I've not seen visible (by
> eye)
> >>defects in the Pyrex disks that are currently
> >>available. I would think that testing through the
> back
> >>would be possible with today's glass.
> >>
> >>Ken Hunter
> >>
> >>
> >>--- Greg Jones <gregj888@comcast.net> wrote:
> >>
> >>> "Pyrex is not homogenous and has a lot of fine
> >>>grain boundaries.."
> >>>
> >>>I've read this in all the old texts too but am
> >>>wondering if it's true (or still true).  Has
> anyone
> >>>checked a Pyrex blank in the last 10 yrs?  Seems
> >>>like to be low expansion it would need to be
> >>>homogeneous, and how do you make it so it is not?
> Has to be annealed too. 
> >>>I'm not saying it's any
> >>>better now than 40 yrs ago, just suspicious.
> >>>
> >>>It's on my "to do list" to check, but still a
> ways
> >>>from the top.
> >>>
> >>>
> >>>Greg Jones
> >>>http://home.comcast.net/~dac20/dac_001.htm
> >>>
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> >>
> >>
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