https://www.youtube.com/watch?v=y-4qqcCxD6g

 

So the following video shows a method; involving hydroxides, silver nitrate, and ammonia, for depositing silver directly onto a surface.

 

1. Could any excess silver (ie. not deposited onto the surface) be re-used?

 

2. Could something like this (make the metal deposit onto the surface) be used with cheaper reflective materials, like aluminum?

 

3. How cost-effective would this be, as a mirror-making method? Does it depend on whether it's a flat mirror, concave mirror, or convex mirror? Would this be good for creating especially large concave/convex mirrors if you already had a large surface onto which to make the silver deposit itself?

1.  Yes, you can precipitate the silver in the excess solution as silver chloride by adding dilute hydrochloric acid (The acidity also prevents the explosion hazard associated with the ammonia/ silver complex).

You can then heat the silver chloride with sodium carbonate  or treat it with zinc and acid to convert it to sliver metal, then redissolve the metallic silver in nitric acid.

2. Just about. You can make copper (and platinum- but it isn't cheap)  mirrors this way but most metals are too reactive. They can't be produced in water because they react with water.

 

3. Well, it's one of the commercial processes for making mirrors.
The usual alternative is deposition of metal- typically aluminium- in a vacuum chamber.
The set up costis higher, because you need a big vacuum chamber, but the running cost is low because you can use aluminum , and you don't have chemical waste problems.

If you want to silver the inside of small glass objects then the chemical method is better.

It used to be the standard way of making xmas decoration baubles.