How to Precision-cut Glass with Minimum Waste
With the current crisis in the glass industry threatening to slow or cut off our supplies of art glass, it now becomes more important than ever to conserve the glass that we have on hand. I’ve found a method for minimizing waste when cutting glass patterns, and I'd like to share it with you.
Here's a picture of a recent pattern that I created for a rectangular glass plate.
I've drawn my design on Mylar, a wonderful translucent drawing film that was created as part of the space program. I think it is perfect for using with glass because it is waterproof, tear-proof, writable, erasable, and can be dried off and reused pretty much forever. (You can choose from two sizes of Mylar on this website).
I draw the pattern on one sheet of Mylar and then trace it onto another. I leave one drawing intact as a master background to assemble the pieces on, and I cut up the other to use as templates for cutting my glass pieces. In this particular design, I'm using more than one color of glass, so I number each piece and label it with the color that I want it to be.
Next I arrange the Mylar pieces for one color on a sheet of glass:
I play with them and arrange them to try to fit them as closely together as possible. You want to just have enough room for your diamond cutting wheel to run in between them. The goal is to minimize the space that the pieces take up so that you can keep the remainder of the sheet intact for other uses. Once you have your cutting layout arranged, it helps to tack the Mylar pieces down with tiny bits of our double-sided acrylic fusing tape.
The yellow lines in the photo above represent the places and the general order in which I'd score the sheet around the pattern pieces. If you examine the photo closely, you'll see that there are many places where the cutting lines intersect. However, if you play your cards right, you can score the larger piece one line at a time, break it apart, and then score and break the other lines. It's important to do a mock “dry run” of each cut to make that your cutting wheel fits into each open “channel” and also to make sure you won't be cutting over any other pattern piece. Most important to arrange are the large and medium pieces. Small pieces can be fit onto the scrap later. Do each cut carefully, double check each cut before you score it, and you'll end up with wonderfully cut pieces and hardly any scrap.
This photo shows how I use my Morton cutting system to line up a cut:
You might have your favorite cutting tools, but I have to say that my Toyo pistol-grip tap wheel supercutter is really fabulous at cutting accurate straight lines. Regardless of what diamond wheel cutter you use, remember that the diamond wheel is actually a couple of millimeters away from the steel edge of your guide. I suggest lining up your template so that the Mylar is just peeking out from under the guide-- that way your diamond wheel will probably run exactly in the channel between the two pattern pieces.
I've recently heard that some stained glass artists start at the far edge of the glass and pull their cutting tool towards them, instead of starting at the bottom and pushing the tool to the top edge. You might want to experiment with this and see if it works for you. Also, I don't use my pliers very much anymore to break long scored straight lines. Instead, I flip the glass over and lightly tap along the score line with the rubberized handle of my pliers. This tends to consistently give me a nice clean break. (If the glass refuses to break, I flip it back over and use my pliers).
I know that all of us have run our diamond wheels along glass and winced as the wheel hit an air bubble or a cleft in the glass surface. This is a good indicator that the score line is not complete and we might have some problems. If you have this situation, use your running pliers to lightly squeeze at one end of the score line, then turn the glass around and squeeze from the opposite end. Squeezing at a tip or place where we want to make sure the score breaks accurately is a better approach than squeezing at the opposite end and hoping that the score makes it all the way across the glass to where we want it to break.
Once I cut up all of my pattern pieces, I leave the Mylar pattern taped in place and go over to my grinder to clean up any irregularities along the edges. The Mylar isn't bothered by the spray of water from the grinder and the tape will hold unless it gets completely wet. Here's a photo of my nearly perfect pieces assembled in place. When everything is done, I can peel off the tape, wash off my Mylar pieces, and file them away for future use.
These photos show a pattern using all straight lines, but of course you can still use the Mylar and double-sided tape for any pattern, including those with curving lines. In that case, I found that my Toyo Thomas Grip supercutter with a tap wheel gives me fabulous control because it rests in the "saddle" between thumb and forefinger.
Of course, the kind of glass you use might defeat any attempts at totally accurate cutting, especially some opal glasses. If you're working with a tricky glass like this, make sure you get your most important large pieces cut first. After they are safely cut, you can place on the rest of the smaller pattern pieces. Another trick that I've used when I'm down to my last piece of glass is to score two lines right next to each other, one on the exact line I want to cut, and the other just outside it. I then use my pliers along the outer score in the hopes that if the glass starts to break crazy, it will run into and along the inner score and not across my precious piece. I might have to do a bit more grinding, but I'd rather do that if it means preventing an unintended break.
I hope this helps you save time, effort and glass, especially in your production work. If you have any other tips on cutting glass, please let me know--I'd love to hear from you!