I used a jig with a small cutting wheel to score the bottle then heat the score line with boiling ( or near boiling for thinner glass) and then dip it in water to break along the line. Polish with emery cloth or high grit sandpaper. The less delta T between the hot water and the dip water the smoother the cut. Finding your preferred Temps for the thickness of the glass is the art.
How do you cut them? I’ve thought of getting a tile saw and doing that.
I used a jig with a small cutting wheel to score the bottle then heat the score line with boiling ( or near boiling for thinner glass) and then dip it in water to break along the line. Polish with emery cloth or high grit sandpaper. The less delta T between the hot water and the dip water the smoother the cut. Finding your preferred Temps for the thickness of the glass is the art.
Edit: Boiling water