Your work surface should be absolutely flat. Any unevenness may cause your glass to break. An uneven work surface will also cause you to score unevenly, resulting in breaks that do not follow the score lines. A workbench covered with commercial or outdoor-type carpeting is ideal if you work with large sheets of glass, but for most hobbyists, a thin padding of newspaper is sufficient.
Keep your work surface free of small glass chips. A small bench brush will do the job and prevent you from being tempted to sweep away glass chips with your hands.
How to Hold Your Cutter.
Hold your cutter however it feels comfortable for you. You may score away from or toward yourself. It may feel a little awkward at first, but with a little practice and experimenting, you will find a way that feels "right" for you.
It does not take brute strength to cut glass, since glass is not actually cut, it is scored. Exerting about 15 pounds of pressure, the wheel of the cutter "scratches" the glass, created a stress point. When pressure is applied to this score line or stress point, the glass should break along the line.
The care and use of your cutter. Keep your cutter in a jar filled with enough lubricant to cover the wheel. Pad the bottom of the jar with a small piece of cloth or paper towel. It is recommended that you store your cutter in this jar of lubricant whenever it is not in use. Before each score, dip your cutter in this solution.
Cutting the Glass.
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Stand to cut glass, so that you may see what you are doing and so that you can get the proper pressure from your shoulder rather than your wrist.
Lubricate the cutter before you begin, and between each score.
When cutting stained glass, always score the glass on its smoothest side.
Hold the glass securely with one hand while scoring with the other.
Begin to cut 1/8" from the edge of the glass.
Maintain an even pressure while scoring. Failure to do so could result in the glass not breaking properly. Your score line should be visible, and a gentle "ripping" sound should be heard. If you don't hear or see it, pressure is too light. A heavy, white, fuzzy line indicates that you are using too much pressure.
Never go over the same score line. Doing so will dull your cutter, and the glass will not break properly.
Make sure the wheel is perpendicular to the glass at all times. Slanting the wheel will give you a beveled edge, or even worse, you will not be scoring the glass at all.
STOP SHORT of the edge of the glass for longer cutter life.
Always do the most difficult scores first.
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If you have to use excessive pressure to score, your cutter is probably dull, or you are using the wrong cutter for the type of glass you want to cut.
If your score line looks like a dotted line, the wheel of your cutter is probably dented, and it should be discarded.