Start with straight lines: Using scrap glass, place a thin strip on your work surface next to a ruler and score across it in a straight line from one end to the other. Don’t worry about making anything in particular. This is just to feel what it’s like to score a piece of glass that requires a simple movement, with no curves, angles, or complex pattern to follow. Straight cuts are great for learning how to handle the cutter because any slight changes in pressure, speed or angle will be very visible.
Position your hand to feel comfortable. You don’t want to contort your wrist. The cutting wheel needs to travel across the entire length of the piece of glass in one movement. You’ll find that it’s more important to move smoothly than it is to move slowly. If your hand pauses midway through, speeds up, or pushes harder toward the end, the score will be affected. Doing this several times will give you an opportunity to practice controlling the score so it’s as consistent as possible.
While the ruler will help you maintain your line, you shouldn’t be pressing the cutter hard against it. Leave some space between the cutter and ruler for the cutting wheel to roll along the glass. Be mindful that the wheel is a few millimeters away from the side of the cutter. You’ll need to bear this in mind when you transfer your pattern to the stained glass and try to match the dimensions of your cut pieces to the design.
Break the glass using running pliers or another suitable technique, and observe how the break relates to your score. A clean break along the line indicates you’ve got the hang of the scoring process. If the break wanders off the line or has an extra corner, check the score. Before you start grinding, you want to see whether it’s broken correctly. Don’t try to fix the problem with the grinder; it won’t teach you what you did wrong. It’s all right to leave your test pieces, since you’re experimenting on scrap glass.
Score several strips of similar width and lay them out side-by-side. They don’t have to be perfect. See which ones scored the most consistently. One might show signs of being pressed too hard; another could have been interrupted. The third should look smoother and have broken more evenly. Comparing these three results is far more useful than looking at one result on its own.
Scoring straight lines is also good practice for scoring curved pieces. While the shapes you cut will vary, the principle remains the same, one steady, controlled stroke, with no need to go over the line again. This makes scoring gentle outside curves much easier to focus on, as there’s less need to consider other aspects of the cutting process.
Avoid tiring yourself out. It’s better to score five neat strips than a dozen sloppy ones. Save a couple of your best test pieces to compare with your later work. When you notice your scores are becoming longer and the breaks follow them more closely, you’ll know your handling of the cutter is improving.