Things You'll Need
Lapidary spinning buff
A watch crystal is the transparent piece that covers the face of the watch. Crystals are typically made from one of three different materials: glass, known as mineral glass in the watch business, plastic (or plexiglass) and synthetic sapphire, which is expensive and highly scratch resistant. Glass crystals are common in most mid-priced and antique watches. Plastic is used in less expensive watches and scratches easily. Removing the scratches from a crystal can renew an older watch and give it many more years of use.
Discern which material your watch crystal is made of.
Apply masking tape around the outside edge of your glass watch crystal to protect the metal finish of the watch.
Dab a small amount of polishing compound on the lapidary buffing wheel by holding the stick of compund on the moving wheel one or two seconds. Buff the glass watch crystal using medium pressure. Keep the watch moving and check it often. If it becomes too hot, discontinue buffing until it has cooled down.
Remove the masking tape when the scratches have all been buffed out. Use a soft cloth to clean any excess polishing compound left on the crystal.
Remove your plastic watch crystal by snapping open the case. Pop out the crystal by applying a small amount of pressure from the outside. It should come out easily.
Wash your plastic crystal with soap and water. Dry it with a soft cloth. Apply a small amount of Brasso to a clean, soft cloth and polish the plastic crystal with it. Buff it with another clean, dry cloth.
Do not force a crystal out from a casing with a great deal of pressure or other tools. This may result in a broken crystal or damaged watch.
Do not repair scratches on a synthetic sapphire crystal yourself. Take it to a professional jeweler instead.