How to Cut Safety Glass

Throughout parts of the 20th century, car windows were mostly made of safety glass. Safety glass shatters upon impact instead of breaking into large pieces like regular glass. In a car accident, it is safer for glass to shatter than to break into large, jagged pieces.

Today, most manufacturers make car windows out of tempered safety glass. Tempered safety glass cannot be cut by hand without shattering it, but regular safety glass can be easily cut. Here's how.


  1. Hold the piece of plywood over the area the window is going to cover. Use the marker to trace around the opening, making sure to leave a few centimeters to allow for the part of the glass that fits into the rubber gasket.
  2. Cut the plywood along the traced line.
  3. Fit the plywood into the opening to ensure proper fit. If it is too big, you can sand down the plywood accordingly. If it is too small, you will need to repeat Steps 1 and 2.
  4. Place the plywood on top of the safety glass and trace around it. Then turn the glass over and trace the plywood again, lining up the tracings on both sides.
  5. Position the cutter over the tracing so that its angled surface is parallel with the surface of the safety glass. Press down firmly and slide the cutter away from you. The cutter should make a gentle hissing sound as it scores the glass.
  6. The cutter can only cut in straight lines, so work around curves by cutting multiple straight lines and breaking off pieces of glass as you go.
  7. Turn the glass over and score the other side.
  8. Tap each side of the glass with the ball on the tail end of the cutter. This should crack the glass along the scored lines, leaving only the plastic membrane intact.
  9. Drip the solvent into the crack to melt the membrane. Alternatively, drip some lighter fluid into the crack and light it. The plastic membrane will melt and you can pull the cut pieces apart.
  10. Sand the edges of the glass with the emery paper to remove uneven surfaces and bumps.