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I don't know a lot about creating lenses or mirror blanks but you have said you are making a mirror. Since you are going to have to grind to get it to the proper shape and then you are going to coat it with a reflective material, I wouldn't think it would matter what glass you used as long as it wa...

Bert I have some unifrax fiberfrax. Is that the same? And is it "wetable" to where it can be molded onto a round shape to contain a telescope mirror? Sort of. Maybe. Not exactly... Fiber blanket can be rigidized to make molds. There are 2 kinds of rigidizers, colloidal silica and colloida...

Yes I generally use material from a single piece of glass. I do however wonder about breaking up different glasses into tiny pieces and what the compatibility will be like in a full melt?

You're right, typical plaster/silica isn't going to hold up long with that treatment. You can use a mullite/ceramic mold, but the separator will be a problem. Line it with at least quarter-inch of fiber paper and you should be OK. I wouldn't guarantee a long life for the mold. Fiber will work, but ...

Bert
I have some unifrax fiberfrax. Is that the same? And is it "wetable" to where it can be molded onto a round shape to contain a telescope mirror?

Can someone give some advise on glass molds good for casting to 2100 degrees. The plaster / silica molds just don't cut it. I am working on telescope mirror blanks How about kiln shelf material?

Hello I am likewise in the learning stages yet of making meniscus mirrors. My plans are to slump flat glass over a precision mold In my case I am making the mold out of plaster silica with chicken wire inside and casting it in a mirror blank that has been coarse ground. I have tried it with scrap gl...

John
I am also attempting telescope mirrors. Have you been to Mel Bartels website. I am planning a 32 in meniscus blank
I am working with 18 at the moment. I have made several successfully. I have one on the MOM now and use it to cast molds also
Ron

Had no clue what I was doing when I started a year ago but Dudley Giberson of Joppa Glassworks helped me build a 40x40 and the electronics to control multiple kilns. Great help and good kiln and he is 1500 mies away
Ron Behrens

32 and larger can have prohibitive wait times. Larger mirror blanks can become exponentially more expensive. Also when you add the complexity of slumping a meniscus blank it starts to make sense to make ones own. Plus all my life I have enjoyed tackling and completing difficult projects. And when re...

This is one I made and am grinding. I need to improve my success rate. I am going to try using some broken glass in a flower pot next and see what happens.

Cynthia
I am trying to make telescope mirrors---and they don't have to be perfect inside--- just well annealed
And I need to achieve consistent results
I have some broken tempered and 300 pounds unbroken tempered
They are quarter inch in size

I am asking these questions because I have 400 pounds of tempered glass. Once it is shattered do the pieces need to be made even smaller?

So would breaking a piece of tempered glass accomplish the same desired result?

Assuming one puts larger chunks of broken float glass and borax into a crucible and melt. Would someone please explain to me what the process of quenching in water does to the glass? Chemically? Or Physically? I read it is then ready to cast.

I am currently working on 12 and 18 in diameter and up to 2.5 in thick. Once I get this down pat I will go up to 32 and 36
In diameter. I also plan to slump the blank over a prepared mold and create a meniscus blank
Ron

That was one of the first sites I came across roughly a year ago. Lots of useful info that I have used. I however want to go further and cast from a full melt in a crucible---- to learn if nothing elss---- and hoping it gives me a cleaner glass result
Ron

I have been experimenting for a year now with inconsistent results fusing and melting plateglass in molds I am at a point of experimenting with using crucibles and doing a full melt. I have come across several references in this forum of using clay flower pots. My question Would this be an option an...