Glass cutting is truly an art! The right tools can make all the difference, along with a steady hand and a dash of creativity. Experimenting with different techniques may lead to some stunning results. Who knew that mastering the angle and pressure would unlock a whole new world of possibilities in stained glass creations? There are lots of factors that result in an accurate stained glass cutting technique. The angle of the cutter head, the pressure and consistency to name a few.

Here are some things to consider when starting your glass journey. Remember nobody is perfect and glass art takes time to master. Be kind to yourself in your glass journey and promise me that you will enjoy every step of the process no matter how long it takes you to learn. Trust me, I am still learning every day!!!

So here we go……

Use a good quality glass cutter. Cutting art glass with a cheap cutter will cost you more in the long run due to inaccurate cuts and breakages. Your cutter should be oil fed with a tungsten carbide steel wheel; inexpensive cutters do not have these features. Choose the most comfortable grip type, there is plenty to choose from, which allows you to apply even and constant downward pressure.

Always select the correct type of cutter for the type of glass. The smaller the cutter wheel the less pressure is needed. The small wheel cutter is ideal for art glass and glass thicknesses of up to 6mm, ticker glass will require a different wheel. There are also specialist circle cutters available to make cutting circles a breeze.

Always use cutting lubricant, it will lubricate the wheel to minimise friction resulting in a cleaner cut and importantly ensure your cutter has a longer life. If you are not using an oil fed cutter either dip your cutter head in the lubricant or wipe some on the glass where you are about to score.

Always score on the smoothest side of the glass where you can apply consistent pressure, scoring over bumps in the glass can lead to the wheel skipping and the score may become inconsistent. When cutting flashed glass such as ‘Spirit’, ‘Opal art’ or ‘Flashed Antique’ cut on the unflashed side. If you score on the flashed side the wheel may only penetrate the thin flashed surface leaving the thicker base glass unscored and this may cause the glass to break unpredictably.

Glass is sensitive to temperature and can be more difficult to cut if it is not at room temperature.

Do not cut your glass if it is just out of the kiln or if the ambient temperatures are extremely cold as you may encounter difficulties.

When scoring the glass use your full body movement, weight, and posture not just your arm to achieve the most uniform score. Always keep the cutter perpendicular to the glass with handle held upright or slightly angled back toward you. Make sure you do not angle it to the side as the wheel will slide on the glass and not score correctly. For complex shape cutting, work at the corner of your cutting bench so you can move around easily as you cut.

Apply uniform pressure and steady speed as you score and listen for a smooth consistent sound.

The sound should be smooth and even not scratchy. When scoring some glasses such as white or opalescent even with the right amount of pressure you may not hear a sound, but the glass will still break successfully. It is important to be confident of your pressure and speed when cutting these types of glass. This skill comes with time and knowing your glass types!!

Always score and break glass immediately if possible. When scoring you must not let the score sit too long before breaking or the score line will begin to develop tiny fractures making it nearly impossible to ‘run’ the break cleanly.

Never score twice over the same path. The score will never be exactly the same line and may cause the glass to break unpredictably; you will also blunt your cutter wheel shortening its useful life. If you have made a bad score and you absolutely need to break the glass along that line then consider turning the glass over and very carefully score along the same path, hopefully the better score will then be dominant, and the glass will break along this line.

Glass will naturally break by ‘Running’ along a score line (A little bit like electricity flows via the least resistant route to the ground)

The score acts as a guide as to where the break must ‘Run’. On a straight cut you must start the ‘Run’ by opening the score with an outward pressure from one edge so it can travel to the other edge. On a more complex shape it can be beneficial to gently ‘start’ the ‘run’ from the middle by applying gentle pressure on the reverse side of your glass moving along the score line to the edge. Always start and finish on the edge of the glass!!! Never stop your score in the middle of a piece of glass as it will have no ‘Guide’ to where the break must ‘Run’ and it will break unpredictably.

Avoid ‘Tapping’ the glass with the end of your cutter to start the run where you can. Tapping almost always leaves a flared or jagged edge. If you must tap, then do it directly under the score line.

Preventing Flares

  1. Always break glass with thumbs when you can, it makes the cleanest break.
  2. For cuts going to a point try starting the run at both ends first before fully separating the glass. You’ll hear a little ‘click’ as it opens the fissure – that’s the glass telling you it’s ready to break apart.
  3. Whenever possible open the glass from where you ended, not began, the score.

You’ll get a little flare at the pressure points of the pliers that can’t be 100% avoided. These tricks will keep them to a minimum.

The Perfect Strip

To achieve perfectly shaped strips, start with a piece of glass four times as wide as the strip you need, cut exactly in half, then cut each half exactly in half. This method allows you to always have an equal amount of glass on each side for your score for a perfect break.

A Guiding Hand

Have you thought of using your non-cutting hand to help guide the cutter head?

We are taught to hold the glass with your non-cutting hand. We are told that the glass will move if you don’t hold it. It’s not that this is wrong, it’s just another way. try the method for yourself. It might feel weird to start with but just try it, it really does help, especially when starting your cut or if you hit a bump in the glass, anytime you need a little shove to get your cutter going this will work!!!

The weight from the cutting pressure holds the glass in place as you cut. It really does make a difference.

It will become easier the more you practise, it might be the accurate cutting answer you were looking for.

Glass Cutting Checklist

  • Always ensure your glass is clean.
  • Stand up to cut if you can. This will help you maintain consistent pressure along the whole score. The optimum height for your cutting table is somewhere between your hips and waist.
  • Check your cutter wheel rolls freely.
  • Keep your cutter perpendicular to the glass. Don’t lean to the left or to the right as this results in an angled break. A perfect scoreline gives a straight break.
  • Keep an EVEN pressure throughout the length of the score. If the pressure varies the depth of the fissure will vary and the glass will break randomly instead of along the score line
  • A score that will result in a good, strong, and clean edge is practically invisible from the surface of the glass. You should see it if you look at the glass from an angle.
  • A white line is indicative of a gouge rather than a true fissure. This is the result of pressing too hard and will not give a good break – the edge will be chipped and weak.
  • A score that will result in a good, strong, and clean edge is practically invisible from the surface of the glass. You should see it if you look at the glass from an angle.
  • A white line is indicative of a gouge rather than a true fissure. This is the result of pressing too hard and will not give a good break – the edge will be chipped and weak.
  • The depth of the fissure is linked to the speed of the cut. The faster the wheel rolls, the deeper the cut
  • If you’re speedy, don’t press so hard! If you’re slower, press harder. There’s no ‘right’ and ‘wrong’ – you might cut a straight line quickly and lightly and a difficult shape slowly, pressing harder. Consistency of pressure is the key.
  • NEVER run along a score twice. This will gouge or crush the glass, it won’t break cleanly, and it will ruin your precious cutter wheel. You can go across a score, just not along it.

Remember…. It may not be you!

There are – very, VERY occasionally – sheets of glass that simply misbehave e.g. some opaques, Chinese manufactured glass. This is normally due to insufficient annealing (cooling down). This happens less and less these days but it’s worth being aware of the possibility.

It’s worth remembering that each sheet of glass needs slightly different pressure applied. Some will make the ‘sssssh’ sound and some – like Bullseye opaques for example – don’t make a noise at all.

Different brands of glass, different thickness and different colours behave… differently! Cut off a small piece of any new-to-you glass to see how it behaves. It will save you glass in the long run.

To enhance your skills further, consider joining the Funky Fragments Stained Glass Classes in Kapunda SA, where you can learn from experienced instructors and connect with fellow glass art enthusiasts.