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Timber
professor emeritus
Reged: 11/08/08
Loc: SW foothills of Mt. St. Helens
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Mirror Blank Annealing Process and Blank Quality
#2867048 - 01/15/09 03:50 PM
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Is someone able to explain and descibe the various types and levels of quality and their processes that the glass companies use to anneal their mirror blanks, especially the larger blanks.
Also, what are the various quality levels used to describe mirror blanks? and how are defects considered in that quality decision?
I can remember the first quality (for me) 35mm camera I bought, it was a Kodak Retina IIIC, bought it about 1956 and still have it, a wonderful little camera, but it had an entrained air bubble in the lens which I questioned at the time and was assured that it would not be a problem being that close, and he was correct it was never a problem, at least to my eye. But that doesn't mean the same kind of a defect would be acceptable in a big mirror.
Richard
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Chris Z
super member
Reged: 03/24/04
Loc: Chicago, IL
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Re: Mirror Blank Annealing Process and Blank Quality
[Re: Timber]
#2869083 - 01/16/09 01:57 PM
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I can't answer your questions, but the first place I would look would be the Yahoo group: ZambutoMirrorGroup. I think this topic has been discussed extensively there.
Chris
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Timber
professor emeritus
Reged: 11/08/08
Loc: SW foothills of Mt. St. Helens
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Re: Mirror Blank Annealing Process and Blank Quality
[Re: Chris Z]
#2870295 - 01/17/09 02:10 AM
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Thanks Chris
Richard
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John Carruthers
Skiprat
Reged: 02/02/07
Loc: Kent, UK
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Re: Mirror Blank Annealing Process and Blank Quality
[Re: Timber]
#2870351 - 01/17/09 04:11 AM
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I don't know the exact criteria but we used to specify blanks as Annealed (commercial), Fine annealed or Precision annealed. Try asking Edmunds Scientific for their specifications.
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Gregg Lobdell
sage
Reged: 01/20/06
Loc: Covington, WA
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Re: Mirror Blank Annealing Process and Blank Quality
[Re: John Carruthers]
#2886235 - 01/25/09 01:02 AM
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Timber (Richard)
Did you get your question answered?
I can give you generalities, but not specifics. Basically, the better the anneal, the slower the glass is allowed to cool. The faster glass is allowed to cool, the more residual stress there is in the glass. See Wikipedia for a good description of the process. http://en.wikipedia.org/wiki/Annealing_(glass)
Residual stress in glass may effect your mirror's figure as it changes temperature.
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