Re: [ATM] silvering vs mercury

[Ken Hunter <atm_ken_hunter@yahoo.com>]

Saqib...
 
Silvering is possible at home and can be fairly dangerous as well as dificult to get good results. The silver coating must be deposited by precipitation, burnished (polished) without scratching or changing the figure of the glass but Mercury IS NOT used as a mirror coating.
 
Typically, an Aluminum coating is deposited (by high tempreature evaporation) on the glass which is very clean and processed inside a vacuum chamber. The coating is only a few molecules thick and does not effect the figuring of the glass enough to matter in all but the most demanding applications. If you have access to a college Physics professor, he should be able to tell you more about the procedure or you can join my other Group on Yahoo called VacuumX for discussions on vacuum coatings.
 
Your vendor cannot know enough to do the job for you if he is telling you that he will use Mercury or that the coating will change the figure. Please do  not commit yourself to any vendor until the books arrive and you have a chance to read about the processes.
 
Ken Hunter
 


Saqib Sajjad <saqibsajjad@yahoo.com> wrote:
hello,


which coating should be preferred? silver or mercury?
if i chose silvering then it will be done in home by
me(no experience yet) while mercury coating will be
done by a vendor.

2nd question, when we coat a concave mirror then
doesnt it sagitta changes? and hence the focal
length.this is the thing the vendor said he will not
be responsible for.


Saqib



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