Wednesday, 12 January 2011

Cutting Bottles

Cutting bottles seems to have a fascination for many people. There seem to be three methods – heat and cold, scoring, sawing.

There are various ways to apply heat and cold to assist with breaking the bottles.

- A string tied around the bottle and soaked in a flammable liquid is a common way to apply heat. As soon as the flame has gone out, you immerse the bottle in cold water; the temperature differential should crack the glass where the string was.

- Filling the bottle with water to the level where the break is wanted and then applying gentle heat with a torch flame at that level should promote a crack.

- Alternatively, the bottle can be scored and put into the freezer for a while and then into hot water.

Scoring is the common method to start a crack.

- This is followed by tapping from inside the bottle with tools from a purchased kit or home-made tappers – a metal ball on the end of a curved piece of metal.

- The score line can also be the preliminary step in the application of heat or cold.

These provide the cleanest edges to the cuts. However there is quite a high failure rate using these methods.

Sawing is method that provides a higher success rate, but is wet, and leaves rough edges to the cut, requiring further cold work.

- Band saws designed for glass can be used, but usually do not have a high enough throat to allow the thickness of the bottle to pass through.

- Most tile saws cut from underneath, so rotating the bottle can lead to a cut completely around. This requires a lot of skill to do free hand, so you need a jig to keep the bottle at right angles to the blade and the bottom the same distance from the blade while rotating the bottle all the way around.