After only smoking joints, I want to step it right up and try make a gravity bong from some glass and get a proper bowl/downstem rather than smoking through tin foil into a plastic bottle. But how do I get the glass to separate? I still live with my parents, and they used to be jewellers so we have some fairly diverse kit, but not a glass cutter. I've tried a scalpel and hitting the score with a very thin point and a hammer, but damn that glass is tough. I also accidentally dropped the bottle from about 5 feet onto lino and there was no trace of damage. Aside from that rather stupid idea, I've only heard of tying acetone soaked string around the bottle, setting it alight, then immersing it in cold water, which isn't much better. I've seen it done in videos and seen it on online guides and what not, but it seems quite like that old 4chan prank of heating up a spoon then cooling it. Basically, people were blinded when it shattered. Sorry for the wall of text, but I don't really want to hurt myself. N.B. my parents aren't completely averse to this but they don't agree with smoking, so I would rather not ask for their help. They worked with metal mostly anyway.