Repairing the silvering on the back of a treasured mirror requires removing the backing paint and the old silver from the glass. While it's not hard to resilver a mirror, it is expensive to buy the chemicals needed to do the job. The chemicals are also extremely toxic and cannot be washed down the sink or poured on the ground, so be sure to have glass jars with secure lids for transporting them to a hazardous waste centre after use. Always wear a ventilator mask, rubber gloves and protective clothing when working with nitric acid or paint stripper.
Lay plastic sheeting on the work surface. Put on rubber gloves, safety glasses, a ventilator mask and protective clothing to cover your bare skin.
Spread paint stripper on the back of the mirror and allow 20 to 30 minutes for it to work. Drag a rubber spatula across the surface to remove loosened paint and stripper, applying light pressure. Scrape the residue into a glass jar, seal it and set it aside. Wash the back of the mirror thoroughly in warm, soapy water, rinse it and let it air dry.
Remove the old silver from the back of the mirror by spreading nitric acid on the surface. Nitric acid is a strong corrosive and will oxidise the silver in a matter of minutes. Wipe it clean with tissue paper. Place the used paper in a separate glass jar and seal it. Wash the glass and rinse thoroughly, leaving no fibres or residue behind.
Apply a thin, even layer of silver nitrate to the back of the glass, using a spray bottle and smooth, even strokes. Allow the new silvering to dry completely for 24 to 48 hours.
Coat the new silver with copper paint and allow it to dry for 24 hours. Finish with a coat of grey latex paint and let it dry for four to six hours.
Always work in a well-ventilated area and wear a mask when using acids or strippers.
Keep chemical residues in separate jars, away from heat and strong light until you can dispose of them. Combining toxic chemicals can produce dangerous vapours and even explosions.