Crafts from recycled glass

You could buy a bottle cutter but you won't be able to get a really nice polished top.

Bottle cutter or file and rubber hammer have near same results. I plan to heat the cut top into a smooth surface.

You need a kiln with a kiln sitter. The propane torch is not useful here, certainly not for fusing. I cut a lot of bottles with a table saw. Mine's made by Covington and uses a 6" diamond blade that spins in a reservoir of water. There are other table saws available at builders supply stores for less than $100. A table saw is much more useful than a chop saw such as most tile setters use, because a table saw allows use of bigger bottles and lets you make all sorts of cuts. A good fume and dust mask is needed. Glass dust, even if wet, is horrible in lungs. With the diamond blade you can cut fast. But the faster you cut, the more cracks you get. Take it slow with little pressure and rotate the bottle as you cut.

John Bassett

You will need to heat the entire bottle and not just the top. Try it and you end up with a broken bottle.

Really? I have mended glass ware by just heating the area that was chipped. Slow heat with slow change in a warm room seems to work for me.

Like I said...try it. Heating up the top of cut bottle is completely different than mending a little chip. I surprised the glass didn't break. some folks who have had success in fire polishing the top of a cut bottle put the bottle in a kiln, heat the whole thing up and then use a torch to fire polish the cut edge. Even that is tricky and you have to know what your doing. A tad too hot in the kiln and the bottle will start to slump. The whole bottle needs to expand and contract at the same rate or you'll have thermal shock. You certainly won't be able to heat the entire bottle with a torch and expect it not to break at some point...unless you have it in a kiln.