Silvering telescopemirrors

[Chriske]

A few weeks back I found this site, explaining 'how to' silvering telescope-mirrors.

For about 40 years now I own my own bell-jar to (aluminium)coat mirrors up to 550mm. In those days I purchased it from a company busy renewing all their machines. Replacing the old with newer and most of all faster machines.
In those days it costed me 'only' a equivalent of 1100€...a bargain..!
I completely rebuilt it to make room for large disks. Only drawback is you constantly need to work on that machine, from time to time replacing parts. It is in fact a time consuming process, maintenance + coating.

But now I will be using this rather old, but renewed' technique to silver a telescopemirror.
A 'kit' cost about 500$ and will silver (and coat) about 27m² of glass.

Someone here already used or planning to use this method...?


 

[johnturley]

I tried silvering a mirror (Brashear's process I think) while I was at school in the late 1960's, it wasn't very successful, the coating was very thin, and rubbed off when I tried to clean it. 

Even if successful silver coatings used to tarnish quite badly after only 6 months, at that time aluminium coatings used to last about 3-5 years. Nowadays modern enhanced aluminium coatings, such as Hilux offered by Orion Optics UK if looked after, last at least 10 years.

John 

Edited March 18, 2023 by johnturley

[callump]

Howard Banich talked about this on a BAA Webinar: 

 

/callump

[Chriske]

12 hours ago, johnturley said:

I tried silvering a mirror (Brashear's process I think) while I was at school in the late 1960's, it wasn't very successful, the coating was very thin, and rubbed off when I tried to clean it. 

Even if successful silver coatings used to tarnish quite badly after only 6 months, at that time aluminium coatings used to last about 3-5 years. Nowadays modern enhanced aluminium coatings, such as Hilux offered by Orion Optics UK if looked after, last at least 10 years.

John 

John, that was 60 years ago, I think you should read this...
btw, the first article about silvering mirrors was written by the famous Mr Porter in Ingalls book ATM I. And it was quit a success, even in those early ATM days.

Cleaning and rinsing is the key to a sticky silver coating.

[davidc135]

When I looked into 'Angel gilding' kits there was a problem bringing the materials into the UK. That was some time ago.

45 years ago I silvered a mirror successfully but I remember there was a lot of scrubbing with concentrated nitric acid. These days I feel more cautious. I tried again quite recently, this time scubbing with pure chalk powder but it was a very poor coat.  

David