How to Cut Greenhouse Glass Perfectly Every Time

You've seen greenhouse glass cut on the telly a million times. After all glass is glass, whether it's in the roof of a glasshouse or the window of a house.

The villain puts a suction cup on a window. You can hear the scratching noise made by the cutting tool as he - it's rarely a woman - drags it around full circle. And then, hey presto - the perfectly cut round piece of glass magically pops out.

Except that it doesn't work like that. If you tried to pull the glass out the way they do on TV or in your favourite action movie, you'd not only break the centre piece, but you'd break everything else as well.

Why is that?

In this brief post, you're going to find out why; but to do that, you'll need to know how to cut greenhouse glass in the first place.


Before you get started, make sure that you are wearing gloves that are designed for handling glass. Not only is greenhouse glass extremely sharp, it's also slippery. You don't want to drop it.


  1. The first thing you need to do is to find a large flat surface on which to work. It doesn't have to be fancy, but it does need to be large enough for you to lay down the pane that you want to cut and to have several inches of empty space on the left and right sides. This is so that you will have room to cut and also so that if the pane moves at any time, it won't injure you by tipping to one side or another. Although you won't be applying a lot of pressure, you will be pressing down somewhat, and you don't want the glass to move off the surface when you do.
  2. If you're dealing with a large piece, then you'll want to use a frame designed for the purpose. The frame will hold the greenhouse glass in place and let you set the cutting blade in a fixed position. You'll only then need to slide it along the surface to score it.
  3. If you're not using a frame, then find a straight edge that won't move. Some people use another sheet of glass. They simple put the one sheet on top of the other. Whichever method you use, make sure that it is straight. Once you score the glass, it will be too late to make changes.
  4. Now it's time to score the glass. Place the cutting blade against the straight edge and steadily but firmly drag it from the top to the bottom of the sheet. You will be able to tell by the sound that is made if you're doing this correctly. It can be likened to that of tearing a carefully folded sheet of paper. You will also be able to feel the scoring as it occurs.
  5. The next step will depend on the size of the piece you are cutting. If it is several inches, then you should be able to snap it off in a single step. To do this, place the scored line flush to the edge of the cutting surface. Grasp the glass in the middle of the piece you wish to break off and then gently push it downwards. This is why all those would-be housebreakers would never be able to cut glass the way you see it in the movies. It's impossible for them to tilt the glass in such a way that it will snap as cleanly as you're led to believe it is.
  6. If the piece you wish to cut is quite narrow, then tap the back of the scored line gently with a screwdriver handle. If you look closely, you'll be able to see tiny cracks forming along the line. To break the piece off, use one of the slots in the cutting tool. One should be smaller than the other. Use the one that is closest to the thickness of the glass you are cutting.
  7. This is another reason why villains can't cut window glass the way that it appears. They can't push one side in without doing so to all of the others; and pulling on the glass won't work either because a) it's not scored on the other side and b) they can't tap the glass from the inside to create the tiny cracks that would make it more likely.

Safety again

Be very careful with the glass when you cut it. Something as simple as running your hand along the edge will be enough to cut you badly. If you are the least bit unsure or are challenged by even small DIY jobs, then it's better to let a professional do this for you.

Please tell us about your experience in the comments section below.

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