Cutting a mirror can seem like an intimidating task, but other than the fact that a mirror is reflective, the method for how to cut mirrors is no different from cutting ordinary glass. It’s not difficult, provided that you take the proper precautions and use the proper tools. The following steps will tell you how to cut a mirror to fit a frame or make a mosaic.
Step 1 - Practice
As easy as this process can be, doing it right does take some getting used to. Stop by your local framing shop and ask for some scrap glass (they'll have plenty of pieces sitting in the waste bin). Follow these steps a few times with scrap glass so that you can get the right “feel” of how the mirrored glass will behave when cut. It's a small step but helpful for you to develop the confidence to handle the real thing.
Step 2 - Safety First
Glass can be dangerous, so take precautions. Lay out newspaper on your cutting table and the surrounding floor, and line your trash bin with newspaper. Keep kids and pets away, and always wear goggles and gloves whenever handling glass.
WARNING: Cutting off less than 1/2 inch of glass can be tricky, and making long cuts (over 24 inches) is always difficult. Take your more demanding projects to a glazier or framer to avoid cutting yourself or damaging surrounding furniture.
Step 3 - Measure Carefully
If you’re fitting your mirror to a frame, measure the inner lip of the frame and reduce this measurement by a couple of millimeters. This will ensure an easy fit. If your mirror is even a millimeter too large, you’ll find it very difficult to properly mount. Trimming the mirror also becomes a real headache when you try to fix that and find yourself trying to whittle off lengths that measure in millimeters. So, it’s best to cut your mirror a touch on the small side.
You’ll be cutting on the reflective side of the mirror, so wipe it down thoroughly to remove any grit. Use your marker to identify the “scrap” side of the cut. In other words, mark the cut line so that it will be removed with the discarded piece of mirror.
Step 4 - Placing the Blade
Position your straightedge on the “keep” side of the cut line so that any wandering cuts will stray into the “scrap” side of the cut. Set your straightedge so the cutter’s wheel is aligned with the cut. Depending on the configuration of the straightedge and cutter, this may be several millimeters away from the cut line. Weight or clamp the straightedge in place and make sure to apply oil to the cutting wheel, or fill the cutter’s oil reservoir if it has one.
Step 5 - Making the Cuts
Firmly draw the cutter along the straightedge from one edge of the mirror to the other. Keep the pressure steady and cut once- not back and forth.
You should hear a smooth zipping sound as the wheel rolls, with some crunching as the wheel rolls over either edge of the mirror. Make sure the cut starts and ends with the edges of the mirror; otherwise, you’ll end up with some ugly-looking corners.
Step 6 - Snapping the Edges
Position the mirror so that the scrap side hangs off the edge of the table and grasp the scrap side with each hand 1/3 of the way in from either edge. Use firm downward pressure to snap off the scrap piece.
Step 7 - Cleanup
Use a soft brush to collect any glass shards and particles. Collect all scrap and carefully dispose of it in tear-proof wrapping such as a cardboard box.