A Look at Glass-Cutting Challenges

BobsBlogGraphic03142014I have written about the lost art of laminated glass cutting in the past, and a client of mine recently called with a request that reminded me of a challenge worth discussing. The request was for cutting a windshield for a front-end loader that had an “inside cut,” “mail slot cut,” or the way my Canadian customer called it, the “female cut.”

The true challenge of this cut is the separation of the scrap piece from the stock piece. The cutter cannot just bend the glass and cut the lamination because the stresses on the stock piece are too great and the stress will cause the glass to fracture into the finished piece. I have seen a number of different ways to accomplish this feat and all worked relatively well, but there are a few that will produce a better finished piece and a higher rate of success.

First of all, I would cut the inside cut first before I cut the other sides to pattern. This way if I am not successful making the most difficult cut (the inside cut), I can at least salvage the largest part of the stock piece for future use.

One of the most popular ways to accomplish the cut out is:

1. Score the glass to pattern on the number one side and break the score with a pair of drop-jaw pliers and finger pressure.

2. Turn the glass over and score the second side directly on the line of the first score and break the second score in the same way as step one.

3. Relief cuts are the key to success with inside cuts. How you do the relief cut is a matter of preference. Some make perpendicular scores to the original cut and others make a series of curved scores until the last curved cut is separated.BobsBlog2Graphic03142014

4. The curved scores allow small glass pieces to be removed piece-by-piece, thus reducing the possibility of stress breaks. The perpendicular scores are broken and run to the previously broken “pattern” cut. In this way, the glass becomes more flexible and sags slightly opening up the crevice between the stock piece and the scrap piece for access to the lamination.

5. This next step is where the quality of the finished product comes in. Many cutters will then soak the area with denatured alcohol and dissolve the lamination by either letting the alcohol eat away at the lamination or by lighting the alcohol and melting the lamination, thus separating the scrap piece from the stock piece.

Obviously, I disagree with lighting the alcohol for safety reasons but I also disagree with using alcohol at all. Even letting the alcohol dissolve the lamination will cause the alcohol to seep between the two layers of glass thus beginning the lamination separation process. The two glass layers will eventually separate and cause a clouding effect around the glass perimeter.

I prefer to cut the lamination with an old tape measure blade. The blade is very flexible and cuts the lamination around the tight corners cleanly and effectively without the possibility of lamination separation in the future.

Once I gave these instructions to my rookie glass cutting client, he commented that it sounded like it might be a little difficult to do. I corrected him and said that it is quite difficult to do and if he succeeded on the first try he is a better man than I because it took me many months of practice to achieve a positive success ratio with inside cuts. I haven’t heard back yet. I’ll keep you posted.