Recovery of Silver from old mirrors

A. I found 2 good sources that gave silver thickness for common mirrors. Both were listed in the definitive book "Silver: Economics, Metallurgy, and Use" [on eBay or Amazon or AbeBooks affil links] by Butts and Coxe One said there was about .15 grams of silver per square foot. At today's silver market of $41.65, this is about $.20 per square foot of silver area. The other said that the thickness can be varied between .0000012" and .0000079". Therefore, using these figures, the value today would be between $.04 and $.26 per square foot of silver area. Not much silver and lots of costs. Lots of handling and it is heavy and fragile - Chemical costs - Tanks and other equipment - Waste costs - Fume control - silver purification cells - etc., etc. The simplest and probably the best ways to do it would involve stripping in either nitric acid or Cyanide. I could easily set up a process for it but, I think it would be a loser. I know of no refinery recovering silver from mirrors and that is usually a good indication that there is no profit in it. Maybe I'm wrong, but I doubt it. Chris Owen - Nevada, Missouri, USA A. Hi Brad I would be very surprised if the cost of chemicals, plant, disposal of waste and complying with extensive regulations did not greatly exceed the value of any silver recovered. It may also save you a great deal of frustration to know that many modern mirrors are coated with aluminium rather than silver. Geoff Smith Hampshire, England A. I don't think there is enough silver on mirrors to justify the processing costs even at a $40 per ounce price. It is a very thin layer deposited by either immersion plating with iron powder, or electroless plating. It is usually covered with a thin layer of copper and a paint-like coating. Lyle Kirman consultant - Cleveland Heights, Ohio

I didn't think of the paint. The paint would have to be removed first, before going after the silver, and that would really make it an expensive chore. Forget it!

A. If you have to worry about the paint, use gasoline to get it off; my grand father owns a glass repair and insulation shop in Michigan when he receives broken mirrors he will remove the silver, he uses gasoline to remove the paint then he melts the silver off of the glass. Good luck.

Thanks Russell. Your grandfather may be right, but I think we need to warn the readers that gasoline is NOT a generally accepted solvent because of its extreme flammability and the horrific accidents that can result.

Gasoline contains 10 percent benzene. Causes cancer. Do not breathe or let it contact skin.

A. Hi Monte. Chris Owen is quite knowledgeable on such issues and said that he knew of no such refinery. No one has challenged that in 7 years now, so best of luck but don't hold your breath :-)

Regards,

A. Hi Monte

Silver can dissolve in molten glass:
onlinelibrary.wiley.com/doi/pdf/10.1111/j.1151-2916.1949.tb18957.x
So you stand a good chance of turning a simple problem into a near impossible one.
Why not simply dissolve the silver in nitric acid?

BUT are you certain the coating is silver not aluminium?

A. Hi Monte. I suspect that a very large heavy old mirror is worth far more than the value of its recovered silver even if the recovery was free and easy, which it's certainly not. People may not get what they're asking, of course, but there are nearly a thousand mirrors on eBay in the $200 to $20,000 range.

Regards,

A. According to the figures I gave in the old post above, the silver content of one square foot of a silver mirror is between 1.5 cents and 9 cents. That is based on the the present silver spot price of $14.70 per troy ounce,

A. Old mirrors make great aquariums after the silver is removed; that's how I came across this.