Mar 75 min read

Tips on How to Break Stained Glass

Updated: May 9

Safety First:

Always keep safety in mind when scoring and breaking glass by wearing safety glasses. These glasses will provide essential protection for your eyes against any potential glass slivers. Additionally, ensure that your work area remains clean and free from glass slivers by using a bench brush and dust pan. By following these precautions, you can minimize the risk of accidents and avoid picking up glass slivers with your hands.

Side Note: Check out my post on Creator's Waffle Grid. It is an awesome tool to use when scoring and breaking glass.

Score on the front side:

Typically, the front side is the smoothest or shiniest. Place the glass on your cutting surface with the front side facing upwards. Lay your pattern piece on top of the glass. If you're working with patterned or textured glass, take note of the directional lines on your pattern pieces. Secure the pattern in place and trace around it with a felt-tip pen. Remove the pattern and mark the corresponding piece number at the center of your glass piece.

Scoring your glass:

For a more in-depth review on scoring glass, see our article: FAQ - Common Glass Cutting Questions. So for now, let’s continue. Let's make sure you achieve a perfect cut! Stand comfortably and hold the cutter just like you would hold a pencil, making sure it is perpendicular to the glass. Begin by placing the cutter head about 1/8" away from the edge of the glass closest to you. Apply gentle and consistent pressure as you guide the cutter along the inside edge of your traced line. Remember, one smooth score is all it takes. Avoid going over the same line or moving the cutter back and forth, as this can result in a poor breaking score and damage the cutter wheel.

When it comes to cutting glass pieces, remember this golden rule: tackle the most challenging cut first and save the easiest ones for last. Inside curves are the trickiest to score and break, followed by outside curves and then straight lines. Glass naturally wants to relieve its inner pressure by following a straight line to the nearest edge when scored. That's why it's best to take your time and break tricky curves gradually instead of all at once. As you gain more experience and understand the glass's limitations, you'll become skilled at scoring and breaking even the most severe curves.

Take a moment to examine your score line. Do you see any small flakes of glass popping up? If you do, it means you're putting too much pressure on the cutter. When you make your next score, try to ease up a little. Are you having trouble seeing where your score line is? It could be because you're not applying enough pressure, so give it another shot with a slightly stronger push.

After you have made the score on your glass, the next step is to break it. There are several different methods you can employ to achieve this. You can choose to use your hands, running pliers, or breaker / grozer pliers. Always remember to break each score line immediately before proceeding to the next one. It is important to note that scoring over other score lines will cause your cutting wheel to wear out faster.

It's not easy to break out severe inside curves with just one score. Start by scoring along the pattern line, but don't break the score yet. To release the inner tension of the glass, make a shallow score near the edge of the glass, running parallel to the pattern line. Use breaker / grozer pliers to break it out. Repeat this process until you reach your initial score. If you experience a difficult break, retrace your pattern piece and give it another shot.

Breaking glass with your hands:

Hold the glass with your fists and thumbs on top (score side up). Keep the glass steady with the knuckles of both hands touching underneath. Center the glass score between your knuckles. Apply pressure with your thumbs and snap the glass by bending the score line away from the score. Twist your wrists to roll your knuckles together from index fingers to little fingers. See the images below from everything-stained-glass.com.

Using Thumbs to separate glass

Breaking glass with running pliers:

Hold the glass with the scored side facing up. Position the pliers at the start of the score, aligning the line on the top of the pliers with the score. Tighten the screw until it touches the lower jaws of the pliers, then loosen it by a quarter turn. Carefully squeeze the running pliers to run the score. If the score only runs part of the way, rotate the glass and repeat the process from the other side. The video below is a great example by Living Sun Glass.

Breaking glass with breaker / Grozing pliers:

Make sure to hold the glass in the hand opposite to the one holding the pliers. Create a fist with your thumb on top of the glass and your fist underneath it, aligning your knuckles with the score line. Position the breaker/ grozers across from your knuckles and parallel to the score line. Apply even pressure while snapping up and away to break the glass, using the same motion as breaking glass with your hands.

When dealing with uneven breaks in your score, it's time to bring out the breaker/ grozer pliers. These handy tools will help you clean up those ragged edges with ease. Simply hold the pliers with the flat jaw facing upwards and snap off any small pieces. If the pieces are too minuscule, try holding the pliers at a 90° angle to the glass edge and gently drag the serrated jaw across it. And if you are still left with some jagged edges, fear not! A glass grinder will be your best friend, allowing you to shape and smooth those edges flawlessly.

Side Note:

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