If your
scoring and breaking of your glass is not going well, you need to diagnose the
reasons. There are always a lot of
suggestions that warming the glass will solve the problem. Yes, warming glass
may help. A discussion of the effect is here. But it will not overcome any faults in the basic skills of scoring.
A lot of
images, shown on the internet, of straight line scores failing to break along
the score, indicate some possible elements in scoring that lead to these
unwanted break-outs.
One possibility
is you are using too much pressure. A discussion of the amount of pressure required is here. You should be scoring to the pressure
required, rather than any sound that may come from scoring. This is emphasised when cutting opalescent
glass. The correct scoring pressure
makes almost no sound or only a gentle rumble as it cutter moves over the
undulations of the glass. The most
frequent reason for more difficulty in breaking opalescent glass is excessive
pressure while attempting to get the same sound as from transparent glass. There are even a few transparent glasses that
make little or no sound when being scored with the correct pressure.
Another
common problem in scoring is keeping an even pressure throughout the
score. It can be difficult to keep the
pressure even on complicated cuts. When
the cartoon has multiple curves or deep concave lines, it can be difficult to
keep the pressure even as you move your body around to follow the line. One piece of advice I received early on in my
learning was to rehearse the score allowing the cutter wheel to move along the
score line with virtually no pressure.
This shows how the piece of glass needs to be oriented to ease your
movement around the glass to make the score.
Slowing
the cutting speed can help to keep the pressure evenly distributed along the
score. Straight lines are often scored
quickly. But, even on straight lines,
slowing the speed can make the pressure more even throughout the score. It can also avoid variable speed during the
scoring, which leads to different forces being placed on the glass. The pressure may be consistent, but the
effective pressure is greater when slow than when fast scoring is used. If the speed is variable, the effective
pressure differs along the score line.
A fourth
thing that may be happening on straight lines is that the cutter wheel is at an
oblique angle to the direction of the score.
This will often be heard as a scratching sound as you move along the
score line. This can be overcome by a
gentle pressure against the straight edge you are using to align your
score. Of course, the straight edge
needs to be held firmly to avoid having it move. Allowing the head of the cutter to have a
little freedom of movement also helps keep it parallel to the straight edge.
All this
is merely speculation about your scoring practice.
You need
to get someone to observe you scoring. They
do not need to be experts, nor other glass artists. They just need to be observant. Tell them
what you are looking for in each of the four elements of scoring and have them
observe only one thing at a time.
First get
scales that you can zero when you have a small piece of glass on it. Score
without touching the glass. Have the observer tell you if the pressure was
consistent throughout the score, and if you are in USA, whether the
pressure was above 7 pounds or below 4 pounds. (For the rest of the world 3kg
to 1.8kg). Practice until you can score consistently at about 2.2kg (ca. 5
pounds).
Second,
have the observer stand a little distance from you. Score toward the observer.
They need to observe whether your cutter is perpendicular to the glass while
scoring and if there is any variation.
Next, they
need to tell you if your head was directly above the cutter all the way through
the score. They will be able to see whether your eye is directly above the
cutter
Is your
body behind the cutter, or do you use your arm to direct the cutter? The observer will be able to tell that when
you are scoring curves. The most consistent speed and pressure is delivered
when the cutter is steered from your torso, rather than your arm and wrist. It slows the scoring action, gives smoother
curves, and more even pressure.
The last
element, you can do yourself. Once you
are doing all the things above, you will be able to hear any scratching noise,
rather than the gentle creaking noise of an even score with adequate pressure. If the scratching noise is intermittent or
only at one point, the likelihood is that you are twisting the cutter head, so
the wheel is not in line with the score line.
