Cutting tempered glass isn’t something to casually attempt at home. It can be done, but it takes time and patience to carry out the task properly. It’s also a long process that involves letting the glass cool for several hours. The alternative is to have it done by professionals who employ specialized laser cutters although this can be expensive. Failure to let the glass cool will simply cause the glass to shatter. Be aware that you need to remove the tempering from your glass in order to cut it.
Perhaps the most important part of the process of cutting tempered glass is annealing. This is when the glass is heated to a high temperature and then allowed to cool. You need to be sure that your craft oven is set to a high enough temperature; it needs to be 900 degrees Fahrenheit to heat the glass properly. Once it’s reached this temperature, you need to remove the glass and let it cool off for a full 8 hours.
This is where the patience comes in; if you don’t wait that long then the annealing process won’t be complete and when you try cutting tempered glass, it’s simply going to shatter. What annealing does is remove the tempering from the glass to allow you to cut it.
When working with glass of any type you need to be sure you wear the proper safety equipment. You should always wear safety goggles, and when cutting tempered glass you also need good thick gloves, since at times you’ll be handling hot glass.
When you do cut the glass, you should only use moderate pressure with the glass cutter. You should go in one long, smooth motion when cutting tempered glass and never run your glass cutter over the glass more than once where you want to cut it.
To achieve a smoother cut, drip the glass cutter in kerosene before you use it. Once the tempering has been removed, cutting tempered glass is the same as cutting any other type of glass.
Breaking the Glass
The easiest way to achieve a good break with the glass is to put a small piece of dowel under the line you’ve made. The dowel should be no more than ¼ inch thick. From there, simply apply pressure down on the glass on either side of the line and the glass will break cleanly.
The pressure needs to be applied steadily. Don’t simply push down hard or you won’t achieve a smooth, clean break in the glass.
Having cut the glass, you still need to eliminate the very sharp edge you’ve made. Use a whetstone for this rather than a file as a whetstone will achieve better results on glass. Simply rub it along the edges to soften and round them a little. That makes the glass much easier and safer to handle, but also has the effect of making the glass stronger which can be important now that it’s no longer tempered.