When it comes time to cut glass, there are several useful techniques, with varying results.
1. Burn and Plunge
Dip a piece of common string in alcohol and squeeze dry, or as dry as it will get without dripping. This string should then be placed on the already marked glass and tied tight. Light the string and let it burn off. Immediately, while the glass is still hot, plunge it into cold water. Be sure the container of water is large enough to allow the glass to completely submerge, as well your arm up to the elbow, so as to deaden the vibration when you strike the glass.
Strike the glass with your other hand above the line using a wooden stick and hitting a sharp stroke. This quick, sharp stroke will break the glass where the burning string has weakened it, as if done by a regular glass cutter. This method may be used to cut bottles in any shape, and to make vases. You can perform many such cuttings on glass.
2. Etch and Heat
First, scratch the glass with the corner of a file or a sharp engraving tool. Have a piece of wire bent to the desired shape you want to cut the glass. Heat the wire until it is red hot and lay it upon the scratch. Immerse the glass in cold water just deep enough to come to a level with the wire, but not quite covering it. The glass will break cleanly.
3. Cut Glass with Scissors
To do this you must score and place the glass under water completely. Then with a pair of ordinary scissors, proceed to cut the glass as you would paper or cloth. This method is, of course, not as smooth a job as the methods described above. The edges will not be as smooth, but for getting a piece of glass down to a size and where the edges are not needed to be smooth, this method is satisfactory.
4. Drill Glass
Get a piece of steel wire and file the wire to the shape of a drill. The wire drill must be tempered as follows: Heat the end of the wire-drill on a flame until it is dull red, then place it in metallic mercury. (Caution mercury is a hazardous substance.) The wire-drill, tempered in this manner, will bore through glass as easily as through soft metal. When drilling in glass, always use oil of turpentine with a little camphor to lubricate the wire-drill.
As you drill, be careful not to drill all the way through from one side, as you will break the glass this way. Drill part of the way, or almost through, then drill from the opposite side to finish. Or, if you cannot do this, as when you are drilling bottles, etc., fill these bottles with water or place the glass in water.
CAUTION—When you use the drill, do not make the cutting edges so sharp or too acute. The drill will cut slowly, but you will have better holes with less breakage.
BONUS—How to achieve rainbow colors for bottles, vases, etc.: Use floating art colors obtainable from most paint stores. Take a pail and fill it with water and drop a few drops of several different art colors on top of the water. Now, take any article you wish colored and dip it into the colored water, move the items slowly back & forth. You now have a rainbow colored article. You can color bottles, vases, and many other articles this way.