From: black47 
To: "Bob Walker" , atm{at}shore.net
Reply-To: black47 


Bob,

Here is a crazy but doable idea if you really want to try a 36" design
the curve for the f ratio you want probably a 3, 4 or 5.

Build a wooden frame with the curve and find yourself a kiln many pottery
place have a kiln more than large enough to fit a 36" piece of glass.
Rent it from them on an off day. you can slump mold the glass to your curve
at low heat 500-700 degrees for a few hours.
I have seen this done before with similar and slightly smaller blanks of
plate glass . You would have to check out the melting specs for common
plate glass an of course it must be cooled slowly so as to anneal
properly., but since its not really melting it won't be re-stressed to
badly. Check with a local college many times there kiln if they have one
only used one or two days a week and they could leave in the kiln to cool
for several days. Also you could pay them via a donation to the school heck
you could get another table top and help make them a telescope!.

I am not crazy this has been done done it myself on small blanks 16"
for someone but they did want a cheap spherical mirror and they did the
grinding have yet to grind mirror.) I could use some advice on grinding big
(4-6") flats though anybody have any experience?


  Joe Cartolano


On Tuesday, February 25, 2003, at 05:44 PM, Bob Walker wrote:

>
> I have just obtained an interesting piece of glass.  It's nice plate
> glass
> 36" in diameter and 3/4" thick with a well finished edge ... okay,
> it's a
> table top.  The question is, what should I do with it???  The obvious
> first
> choice would be to make a 36" mirror out of it.  From my readings on
> the
> List and elsewhere, I tend to think this is impossible.  But, the hope
> that
> springs eternal and all that impels me to ask, has anyone tried it?
> What's
> the biggest 3/4" mirror you know of? (Successful one, that is!  Mel?)
> Another intriguing thought is grinding four 14" or so off-axis mirrors
> out
> of it.  That has the advantage of being feasible, at least marginally
> so.
> Then, of course, it could just be chopped up into a number of small
> blanks -- seven 11 inchers or five 12 inchers plus a 10" ... etc etc.
> Any
> suggestions on practical ways to proceed will be welcome.  I've got
> plenty
> of time to mull this over; I don't expect to have my current projects
> completed for a year!
>
>  *  Best regards, Bob
> *
>          *           *   *
>
>             *         *
>
>

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