Running the Score
On Stained Glass

Running the score is the next step after you have scored the glass. It is the technique you use to break the piece out. I'll show you seven ways to do it.

Always start from the edge on which you ended the score. If you try to run it from the starting edge, there's a better chance that the glass will not break out well, or at least with more difficulty. The reason is, when you start a score, you do not start exactly on the edge of the glass. However, you do end the score by rolling over the edge of the glass. So, the edge that you end on is always the best place to start running the score.

Using Your Hands

Double Click on all pictures to make them larger.

This is first way of running the score. It is one of the techniques I use most often. It is quick since you don't have to stop and pick up another tool.

placement of hands

Make a fist. Now grasp the glass and rest your thumbs on top of the glass on either side of the score. Your fists are underneath the glass, with your index fingers, curled up, directly on either side of the score.

snap and pull apart

Snap the glass just like you would snap a twig or a bean. Always snap up and out. As you snap, pull your hands apart. This is extremely important to prevent cutting yourself. If you glass is larger than one square foot, rest the back edge of the glass on your work bench as you snap it. Once it is separated, resting on the bench prevents it from falling out of your hands and breaking.

Running The Score With
Running Pliers

using running pliers

To learn about using Running Pliers,
click here:
Running Pliers

Running The Score With
Breaking Pliers

Breaking pliers are used much the same as breaking with your hands to run the score. The only difference being, the pliers take the place of your dominate hand.

If you are trying to separate two very small pieces, you can use two breaking pliers, one in each hand.

There are two types of breaking pliers. Plain breaking pliers with smooth jaws, and breaking and grozing pliers with serrated teeth on the jaws. Either type works when you are running the score. There is a curved jaw and a flat jaw. Just remember that the flat jaw goes on top.

placement of breaking pliers

Place the jaws of the breaking pliers next to the score. Grasp the glass, on the other side of the score with your hand, thumb on top and index finger curled underneath, next to the score line.

placement of breaking pliers

Snap by pulling down with the pliers and
your other hand at the same time. Pull the
two pieces apart as you are snapping.

Running The Score With a Nail

Yup..a nail! Actually anything small and round will work. I had a student that went on to become quite well known in her field of stained glass art. The only thing she ever used to run her score was a golf tee.

placement of nail and thumbs

Place the nail directly under the score.
Place your thumbs on either side of the
score and press down firmly.

a clean break

Running the score is completed.

a clean break

Different glass and different nail.

Running The Score With a Ruler or Straight Edge

Anything that is straight with a thickness of around 1/8 inch will work to run the score. A wooden ruler works very well. In the pictures I used a paint stirrer.

placement of straight edge

Place the ruler/straight edge under the score.
It is best if it goes the entire length of the score.

placement of straight edge

Press firmly on either side of the
ruler, as shown in the picture.

Running The Score Over
The Edge Of The Table

This method is used for straight scores on large sheets of glass. It is easy to do and does not requires the use of additional tools. If you have a sheet of glass that is one foot by two feet or larger, this is the best method for running the score.

pull the glass to the edge of the table

After you have scored the glass, pull the glass to
the edge of your work bench, so the score is about
1/4 inch in from the edge. Do not have the score
right on the edge or over the edge of the work bench.

lift the glass 5 or 6 inches

Holding the front edge of the glass with both hands, lift
the front edge of the glass off your work bench so the
score is five or six inches above the work bench. Now
sharply yank the glass down against the work bench.



It does take practice to learn how hard to yank/smack/slam the glass down. You can't be wimpy about it, but neither do you want to be so physical about it that you break the glass and cut yourself. Practice on some cheap window glass to get the feel for it.

One other note: Please remember to use two hands. Yes, I know I have only one hand showing in the pictures. As my mother always told as I say, not as I do!!

Upside Down

If you have a piece that will not separate, no matter what you do, this method of running the score should work. I use it for running circles, but it works equally well on any score line.

The photographs will be showing how to run a circle and get it out with little effort, but again, use the technique for any score, especially the difficult ones.

You will need a surface with some "give" for running these scores. I use a pile of newspapers. Usually 2 sections of the Sunday paper, in their original folded state, works very well. A spongy computer mouse pad works well also.

Mark the score with a black marking pen. If you are using transparent glass you need to do nothing else except to flip the glass over so the score is on the under side. You should be able to see the marked score line through the glass.

If your glass is opaque, turn the glass upside down on a light box. The light will make the marked score line visible on the back side. Now you can trace the marked score onto the back of the glass.

If you don't have a light box, hold the glass up to a sunny window.

The last step before running the score is to place the glass, with the scored side down, on the pile of newspapers. Now you are ready to go.

placement of thumbs

Press your thumbs all along the back side of the score, making sure you go from one end to the other. Only press hard enough to see the score running. In this picture, you can actually see a section of the score that has run.

On a score that isn't a circle, this is all you will have to do. The piece will be separated by the time you get to the end of the score, and will be free from the glass around it.

making the 4 scores

With a circle there are several more steps.
You will need to make four scores out from the edge of the circle, one on each quarter of the glass. Make sure you start the scores so they aren't touching the edge of the circle; 1/16 of an inch away is plenty.

turn glass over and press the 4 scores

Turn the glass over again, so the four scores
are underneath, Press on the four scores and
they will separate, freeing the circle.

turn glass over and press the 4 scores

This is what the edge of the circle will look like.
It will be clean and free of burrs, ready to be
foiled or leaded.

If you have any questions or comments about running the score,
please feel free to Contact Me

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This page was last updated on March 5, 2016

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