How do I cut the bottom off a glass wine bottle?
There are a few different ways to do this, but most of them involve extremes of temperature: first intense heat along the line where you want to cut the bottle, and then submerging in cold water, repeated several times if necessary.


A Song of Water and Fire

This method assumes you have a tool with which to score the glass, for instance a glass drill bit or glass cutter, both of which should be reasonably inexpensive to get hold of. First use this to mark the line along which you want to cut the bottle. Then apply heat to this line; you can do this in a couple of different ways:


by rotating the bottle slowly over an open flame, making sure the flame is directly under the score line so that it doesn't heat too broad an area of the bottle
by pouring a thin stream of boiling water onto the score line from above, again trying not to let it cover too wide an area



After heating the bottle up along the score line, dunk it in a pail of cold water (which you should have prepared beforehand). The shock of passing from heat to cold should weaken the bottle and make it likely to crack along the existing score line.

It's likely that the bottle won't break the first time you do this, but keep repeating the process multiple times (heat, cold water, heat, cold water) and eventually the bottle should snap in the right place.
String and nail polish remover

Again the basic idea is to alternate extreme heat with extreme cold, but this time you don't need to have a scoring tool because you'll be using a piece of string. You also need something containing acetone, the most commonly used example being nail polish remover.

Take a piece of string, soak it in nail polish remover (or anything else acetoney), and wrap it around the place where you want to cut the bottle. Then set the string on fire, which will apply intense heat to the narrow area on the bottle around where the string is tied. (Obviously, you need to take care that the string doesn't slip to a different position on the bottle. Even more obviosuly, make sure you don't have any of the acetone on your fingers and that the bottle of nail polish remover is placed well away from the flame.) When the flame burns out or you feel enough heat has been applied, dunk the bottle in a pail of cold water as before to provide the stress necessary to crack it.

Again, this is unlikely to work the first time, but you can keep repeating the process, either re-soaking the string to light it again or replacing it by a new piece of string if necessary.


Whichever method you use, the bottle may not snap completely cleanly, so you should use some sandpaper to smooth off the edge of the broken bottle before using it.

You can see pictures and videos of the process here and here. I'll try to add some images and hopefully gifs to this answer later on.

There's also an urban myth that you can cut glass underwater with just an ordinary pair of scissors. I'm not sure whether or not this is true, and I haven't gone to research it, simply because it wouldn't be relevant for your problem anyway. A rigid object in the shape of a hollow cylinder can't be cut with a pair of scissors whatever material it's made of; the underwater cutting, it true, would only work for flat panes of glass.