This time I show you how to cut square ( or any other) glass bottle in 3 simple steps.
How I made it - you can check by looking DIY video or you can follow up instructions bellow.

For this build you will need:

Materials:

Glass bottles

Hot and cold water

Sand paper 80 and 280 grit

Tools:

Glass cutter

Kettle

Glows

Step 1: Preparation

First of all its need to make one nice pass with glass cutter. To do that in one straight and at the same height line, I made this simple jig from two pieces of scrap wood.

Step 2: First Step - a Cut

I’m using regular glass cutter which you could get at any hardware store for few euros.

It’s need to make one strong pass all around the bottle. It’s important to make only one cut. Do not try to make few pass to get deeper cut. That don’t give any better results, vice versa - it could make multiply splitting lines.

Step 3: Thermal Stress

Prepare some boiling and cold water. The idea is to use physics and let thermal stress to do all job. First, to heat it and after that very quickly cool down. When heating, it’s important to heat evenly as possible all around at cut line. Cold water will make quick thermal stress and cut line will crack.

In this method to cut round bottles is very easy, because round bottles have equal surface tension. With square bottle we have different surface tension at sides and corners, so be ready to fail. Not all square bottles you will try to cut - will be done successfully.

Step 4: In Process...

Some time you will get only a part of glass off, not full top. Take your time and repeat the process at rest cut line. At this situation you could give a light tap to make it done faster.

Even when you did everything right, sometimes you don’t get nice cut or will get crack where you don’t need it. That’s because all bottles could have not visible mini cracks and your cut line could change direction.

Step 5: Sanding...

To smooth the edge I used 60 grit sandpaper and wet sanded to acceptable result. To get nice finish look I finished with 280 grit sandpaper.

Step 6: Result

And here is final result. No sharp edges, nice and glossy surface.

Step 7: Where to Use It?

What about purpose? Well, it depends only from your imagination. Here few examples from me. You could serve some snack in it. Or to store some kitchen tools. It also could be a big glass for drink. Or unique vase.