How to Cut Glass

While work on my daughter’s bedroom renovation feels like it is going excruciating slow, we are making progress. The window in this room is my most complex window restoration to date. Mostly, that is due to the fancy window lite pattern on the upper sash. I thought I would write a quick post to explain how to cut glass. Many people leave it to the pros, but it’s such a low-tech and simple DIY that I highly recommend learning how and add it to your skillset.

You’ll get the most value from this tutorial by watching the method in action, so I made a video. You may watch it below or directly on YouTube.

How to Cut Glass – Tools

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To cut glass, you don’t need anything fancy or expensive. Here’s the list:

• Glass Cutter
• Glass Cutter Oil
• Safety Glasses
• Gloves – I’ve linked to size medium because one size does not fit my dainty lady hands.
• Pliers to snap off small pieces – nothing fancy here
• Soft squeeze clamps (optional) – I often use clamps like an extra set of hands. If you choose to use clamps for this project, they must be very soft, or they might crack the glass.
• A few putty knives

The Method

First, I want to give credit where credit is due. I learned this glass cutting method from my friend, Steve, at Wood Window Makeover. He is a kind and patient teacher. This technique has been passed around for some time, and I am grateful that Steve taught me. Learning how to cut glass this way is a huge time saver, and I no longer outsource the task.

Note: In the video, I used a piece of new glass. For some of the photos below, I cut a piece of wavy glass salvaged from my office window. When I was restoring my office window, I accidentally broke off one of the corners. That meant that I could not use it for that window again, but I saved it for a smaller project like this one. Both types of glass are straightforward to cut, but wavy glass can be slightly thicker. The stakes are higher with wavy glass since it is irreplaceable. So, keep that in mind while you are learning.

Line up two of the straight edges of glass about 1/16″ from the edges of two adjacent muntins. I completely eyeballed this measurement, and you should too. The key point is that you want the glass to fit in the rabbet once you have all your cuts made.

Clear glass is really tricky to see in photos, so I recommend watching the video for a better explanation.

If you look closely below, you’ll see that the glass extends past the rabbets on the upper and lower left. On the right side, you can see the edges in line. Setting it up this way, there are two cuts to make.

Place some putty knives under the glass that you lined up with the rabbets. The putty knives take the pressure off the center of the glass while it is not setting on anything stable.

The picture below shows the the putty knives in action after I made the first cut.

Put on your safety glasses. To score the glass, dip your glass cutter in the glass cutter oil, and roll the wheel back and forth a couple of times to distribute it. Then, place the wheel firmly at the start of your cut. Grasping it with two hands offers the most control.

Eyeball just inside of the muntin. That’s where you’ll want your score line to be, so the glass will fit in the rabbet.

Firmly draw the cutter wheel across the glass, keeping your line. Make sure it goes all the way off the opposite edge from where you started.

Important note: The cutting wheel should make a scratching noise across the glass. That noise means it is scoring the glass. If you don’t hear the scratching noise, nothing is happening on the glass. If you hear it partway across but not all the way across, the glass will not snap off properly in the unscored sections, and the entire piece could break too. Practice on a piece of scrap glass to get a feel for the amount of pressure you need to apply to the cutter to produce the scratching sound.

To remove the cut section, grasp the piece with gloved hands. Firmly snap along the score line using the window or a table edge as leverage. It should not take much effort.

If you find you are nervous at first, that is totally normal. When I first learned this glass cutting method, I had to give myself pep talks before I even started. Now, I’m down to a few weird rituals, such as tapping my cutter a few times before I commit to each cut. Take your time, wear the safety gear, and know that you will break a few pieces of glass during the learning process.

If you have any questions, please let me know in the comments, and feel free to pin this for later.

This weekend, I will be building the headboard for M’s bedroom and glazing this window too. I am still about two weeks out from reinstalling her window, but we are moving into the home stretch now. Be sure to watch all the fun in real-time over on Instagram.

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