I don't use candles as much now that I've discovered the wonders of LED flashlights, but candles still have their place.
I've spent many nights in a fairly rough camp where it is often windy. My unprotected candles would either blow out, or the wind would shorten their life by blowing the flame sideways thus melting the little 'dam' that holds in the pool of molten wax and allowing the wax to flow away.
I pondered the problem and eventually came up with the idea of using a bottle to make my own cheap version of a hurricane lamp. I was delighted when I managed to remove the bottom of a bottle in a relatively neat manner. I sat the bottle inside a shallow food can. The candle sat in the middle of the can held in place by a bit of steel tubing. I hung the lantern by attaching wires to the can base and taking a wrap of wire around the bottle. It was a bit complicated.
A while after, my brother saw a lantern which was much simpler in construction so I immediately adapted the idea for my own needs. Here is the latest design:
These lamps perform wonderfully in windy conditions. However they do create a LOT of heat, so they aren't suitable for small tents. They should hang well below a ceiling to allow the heat to dissipate. The top of the bottle gets extremely hot and you cant touch it. However you can generally hold the bottom of the bottle if you need to lift the glass to blow out the candle.
In most cases no special extra holes are needed in the base to allow air entry because the sheetmetal base and the cut around the bottom of the bottle are seldom smooth enough to make a tight seal.
The first bottle bottom was removed by filing a small groove in the glass near the base using the corner of a file, then holding a red-hot poker against the groove until a crack started. I then pulled the poker around the base and the crack followed.
Other bottoms were removed by shaking a 100mm nail (or other long metal objects) up and down in the bottle until the bottom dropped out. There was quite a failure rate with this method. Sometimes the break was too uneven and jagged, other times the nail popped out through the side. As you shake the bottle, the first few impacts of the nail create quite a ringing 'ting' sound. When a crack starts the sound changes (to a 'tonk' maybe) and you know things are happening. If I got a 'keeper' I would smooth the edges of the break with a sharpening stone before using the bottle. I came across this method in an on-line article where someone was describing how they get bottle bottoms for knapping.
I think the best, most reliable and neatest way I've used so far for bottom removal is to use a glass cutter. The glass cutter has to have only just enough pressure against the bottle to make a light mark. Often when you are using a glass cutter it will make a certain light crunching noise and you can take this as an indication that things are going well. I believe you should only make one pass with the glass cutter. Care needs to be taken to ensure that the beginning and end of the cut match up. You could set up a bit of timber on a bench and roll the bottle against it while holding the cutter steadily in one place. The next thing I'd do is get a jug of very hot water and pour a small steady stream of water over the cutter mark while you are rotating the bottle horizontally (above a bucket or sink). This alone probably wont cause the bottom to drop off. While the bottle is still hot, run a steady trickle of cold water over the cut in a similar manner. Hopefully at this stage you will see a crack form right around the bottle through the wall. You could then use a rod of some sort that will go down through the bottle to give the bottom a firm tap. Or you could fill the bottle completely with water to overflowing and sharply slap your palm flat against the top of the bottle to create a hydraulic shock and see if that works. When slapping or tapping the bottom to break it free, the bottle should be held in the air in one hand and slapped with the other to allow the bottom to fall away freely.
I've recently seen a demonstration of somebody cutting off a bottle bottom on You Tube, but I didn't bookmark the page.
Here is a relatively poor photo of a candle lamp in action in a relatively crude hut: