Things You'll Need
Heavy paper or light cardboard
Cutting a mirror calls for the same procedure as cutting glass — with the proviso that you need to take care not to scratch the back of the mirror, which bears the thin coating that creates the mirror, while you're doing it. Cutting glass, however, is a misnomer. We don't cut the glass; we scribe a score line along which we will break the glass. Be warned that you may not be able to do this successfully the first time you try. Practice on scrap glass or mirror until you can make the score line the right depth and smoothness. It's a little challenging at first, but very satisfying to get it right in the end.
Prepare a template of the curve you want to cut. The template can be made of heavy paper or light cardboard. Draw (or trace) the shape onto the paper or light cardboard. Cut it out.
Position yourself at a work table that is no higher than your waist, standing with your legs slightly apart and with room for your cutting arm to move freely. Put the mirror (mirror-side-up) on the table in front of you, cushioning it with a dozen sheets of newsprint underneath.
Place the template on the mirror where you want the curve to be. Keep in mind that you cannot start a cut in the middle of a mirror using this method. Start at an edge of the glass and trace the shape of the template onto the mirror with a marker pen. Extend the cutting line to another edge of the mirror if necessary.
Position your glass cutter at the beginning of the cut about 1/16 inch from the edge of the mirror. The cutter wheel must be perpendicular to the mirror.
Put on your safety goggles. Move the glass cutter along the inside of the guide line using a firm pressure and a smooth, slow, continuous action. You need to cut a scoreline that does not have gaps and that does not chip out any little pieces of glass along the edges. Too deep a cut (indicated by chipped edges) will result in gouged-out edges or a broken mirror. Too shallow a cut (indicated by a line that is not continuous or is very difficult to see) and the mirror will not break along the score line. If you can see gaps in the score line, you can try drawing the glass cutter across just the gap. Do not go over any part of the score line that was successfully scribed with the glass cutter.
Put on your work gloves. Take up the piece of glass in two hands and push downward on both sides to break the glass along the score line.
The deeper the curve, the more difficult to cut it successfully. Start with gentle curves and work your way up as your skills improve.
Never break a piece of mirror by laying it on a table with the mirror on one side of the score line on the table and the mirror on the other side of the score line unsupported. The chances of a bad accident are high.