Over time the silver on the back of antique mirror glass wears thin and flakes off. The wavy irregularity of old glass lends a lovely charm to antique mirrors. Other unique features on old glass mirrors can be intricate etchings, bevelling or fancy edge work. The decision to restore can be a tough one to make. Careful thought and planning are important before deciding whether you should restore the antique mirror glass or give the work to a professional.
Assess the value of your mirror. The mirror could be an essential part of the appraised value of your piece. In some cases having the mirror resilvered by an expert can increase the value. Professional resilvering rarely brings down the value of an antique mirror
Restore the mirror glass if it is not of any risk to the value of your piece. Carefully remove the glass with a flat-blade knife or screwdriver from the frame. Wear protective eye gear and gloves.
Study the back of the mirror after it is removed. It could be a larger job than you want to take on. Notice that hand mirrors are filled with pitch before the mirror is put in. The pitch often breaks up into lumps. Remove all of the pitch and save it.
Scrape off all the old silver and clean the back. Wear a dust mask; old mirrors contain mercury.
Re-create the back of your mirror. Prepare sizing that is needed for the silver to adhere to the glass. Slowly heat one cup of distilled water and one teaspoon of unflavored gelatin granules. Stir with a 2.5-cm (1-inch) paintbrush until the gelatin dissolves. Keep the solution over a low heat while you work with the silver.
Use the 2.5-cm (1-inch) paintbrush to apply a 7.5 cm (3") area of sizing to the clean, dry surface of the glass. Generate static electricity to the tip of the gilder's brush. Never touch the silver leaf with your hands or get it wet. It is very delicate and will dissolve. Hold the silver-leaf booklet at a downward angle and touch the gilder's brush to the edge of the silver-leaf sheet. Slide the silver-leaf sheet about 2.5 cm (1 inch) over the booklet's edge.
Touch the edge of the silver leaf to the moist sizing on the glass while quickly moving your hand away from the glass. The silver leaf will slide off and adhere to the glass.
Cover the entire glass, laying the silver leaf in rows. Overlap the squares about 3 mm (1/8"). Let the mirror dry for about an hour.
Apply acrylic clear coat to the back of the silver to seal the mirror. Let the mirror dry overnight.
You are now ready to put the mirror back into its frame. For the hand mirror, replace the pitch by melting it in a pan and pouring it back into the mirror frame.
If your mirror has one small area of missing silver, then work only on the damaged area. Fill in the missing spot with a dab of sizing and cover the hole with a scrap of silver leaf.
Old glass may have built up stress that cannot be seen and may break when you remove the mirror from its frame. This is rare but can happen.