Mirror re-silvering, or refinishing, was once considered to be a trade art. Today, it is a project you can DIY. Most of the materials required for re-silvering can be purchased from any hardware store. A mirror is often a glass with a silver backing.
Before you begin refinishing your mirror, be certain that you have adequate ventilation. The concentrated solvents used to remove the old mirror backing contain chemicals that can be harmful when inhaled, and other chemicals used in the re-silvering process have the same properties.
Make certain the fumes are removed from the work area as quickly as possible, either through the use of dedicated blowers or simply with a shop fan that can move in the fresh air.
Remove the Old Surface Material
The first step in re-silvering is to remove old coatings. Begin with an industrial-grade paint remover, and work the surface to be cleaned with liberal amounts of solvent. Once the paint is removed, use a solution of nitric acid to remove the old silver.
Safety is the primary concern during this process, both due to the harsh chemicals involved and the danger of cuts resulting from handling rough glass edges. If you have access to a painter's respirator, use it.
Clean the Surface Thoroughly
Once the paint and silver have been removed, clean the glass thoroughly to remove any dirt or debris. Materials that are caught between the silver and the glass will show up as blemishes in the finished product, so it is essential that the surface is completely clean. Avoid cleaning solutions that may leave behind a residue or film, as these may cause the silver to improperly bond to the glass.
Apply Silver Nitrate Evenly
The next step is to reapply the silver. To do this, the glass is evenly coated with a silver nitrate mixture that bonds directly. This coat must be allowed to dry completely, and many experts say that allowing it to cure for 24 to 48 hours is the optimal drying time.
If any blemishes or blurs are visible on the glass when viewed from the uncoated side, then you may have to repeat some or all of the process, paying special attention while cleaning.
Add a Coat of Copper Paint
Apply a coating of copper paint, which seals in the silver. Cover this layer of metallic paint with one or more coats of gray paint. These final layers help prevent scratches and damage to the reflective coating. Allow each coat to dry thoroughly before applying the next one.
Allow Enough Time for the Job
Re-silvering a mirror is not an overnight procedure. The glass has to be left to dry and cure between each coat of material, so make sure that you have a work area that will be undisturbed for several days to a week.
When completed, the mirror will effectively be brand new, and this process is much cheaper than trying to find or cut special replacement glass.