Pump spray mirror silvering kit

[Dr Paul Leyland]

Thanks Callum.

An impressive process. 1.8 pounds of silver for each treatment! I hope they recovered the excess.

[Alan Snook]

Callum, yes, I will prepare a paper for the Jounal once I’ve gained a little more experience. I suspect it is a process where you learn sommething new each time.

[Alan Snook]

I cannot answer the question how long the silver coating will last from my own practical experience, as I am new to this. Time will tell.
The short answer must be “it all depends.” Having purchased a decent quantity of all the chemicals required, the cost of each re-coating is small.

I have found this informative article on the Sheffield Assay Office website:
https://www.assayoffice.co.uk/news/ever-wondered-why-does-silver-tarnish
They surely know what they are talking about. Clearly their advice is not specific to telescope mirrors but the priciples will be the same.

Presumably anti-tarnish paper could used to line mirror covers. The paper is available on Ebay in small quantities. The jeweller in a local town can order in bulk, by the ream. My dictionary tells me a ream is 516 sheets! I don’t yet know at what cost.

I have a recollection of reading in an old book that alum paper will delay tarnishing. The item included a recipe for making alum paper.

[Dr Richard John McKim]

No doubt that sulfur, in the form of hydrogen sulfide, is the enemy of silver. The family silver needs a clean from time to time, but if it is just plated it needs to be done as rarely as possible. Sulfur is also the traditional enemy of art galleries in industrial cities. Old Masters used lead sulfate as their preferred white pigment, and over the years the surface of the paint would turn to lead sulfide, which is black, clearly the opposite of the artist’s intentions! The remedy here is to treat the surface with a solution of hydrogen peroxide which oxides sulfide back to sulfate, but that is not the answer with a delicate silver film. Best answer for a mirror is to keep it dry and airtight. For my aluminised mirrors I always used a piece of muslin stuffed with cotton wool which is placed right against the mirror surface. I don’t know what these modern anti tarnish papers contain, but I suppose that if you soaked a strip of paper with copper sulfate or lead acetate or lead nitrate solution and let it dry, the paper would absorb the gas in lieu of the mirror film. It should not be in contact with the mirror surface. You would then see the paper gradually take on a brownish or black tint with time, depending upon where you live. In fact chemists use lead acetate paper as a practical test for H2S gas. It goes black even with traces of the gas, long before the smell becomes apparent. I read that musicians sometimes use the anti tarnish paper in instrument cases. I don’t personally, but it would be effective for an instrument with silver plated keys, such as a flute. (Nickel plating is common, and does not involve the same problem.)
In conclusion, yes to the anti tarnish paper, yes to keeping the surface dry and as airtight as possible, and you can always try to make your own anti tarnish paper if you like! Just beware that lead and copper salts are poisonous.

[Dr Richard John McKim]

I (or rather my iPad) meant to write oxidises rather than oxides (line 5) of course.

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