Reply To: Pump spray mirror silvering kit

[Dr Richard John McKim]

I have seen videos of these kits in action and the results are impressive. The chemistry is nothing new, and I have used the materials over decades in my professional career when doing some chemical tests for reducing agents. The most important thing is to have the surface absolutely clean. If silvering a test tube or glass flask I would normally warm it with some concentrated nitric acid, but the acid can be added in the cold, as you would have to in the case of a mirror, or swabbed over the surface with cotton wool. The use of tin (II) chloride to sensitise the surface is also not a new invention, but is important in the spraying process for with that method the silver-based and reducer chemicals are in contact just briefly upon the surface of the mirror, and the pre-treatment with this powerful reducing agent will enhance the deposition rate of the silver. The price of the commercial kit is very high. Why not make your own? All the chemicals are readily obtained and silver nitrate can be bought for less than £2 per gram. You should not need more than 5 grams. There is a 12 page discussion on the Cloudy Nights Forum. Temperature is important. A warm day would work better, for in the lab one has to warm the reagents, and a large cold mirror surface will cool the spray. Again this is discussed at the Forum I mentioned. I would be inclined to have a go myself first at spraying a small test piece, rather than buying a kit. If you need any chemical advice I will be happy to help (by email).