Weird Science: Cutting Glass with String

Things you will need:

  • String
  • Large Bowl
  • Water
  • Ice
  • Lighter fluid
  • Matches or lighter
  • Glass bottle
  • Eye protection
  • Gloves

The Experiment:

Please do all science experiments under the supervision of an adult. This experiment is especially dangerous so please have adult help you. Fill your large bowl with water and some ice. Wrap the string around the point of the bottle where you want to cut. The thinner the glass is, the easier it will cut and will have a straighter edge. With your gloves on, soak the string with lighter fluid, making sure not to get any on your hands. Remove and wash your gloves with soap and water. Holding the bottle over a fire safe surface, light the string on fire. Let the string burn until it the fire burns out. Immediately after the fire burns out, place the bottle into the bowl of cold water. The glass should crack. If not, tap the glass with the back of a spoon at the break point where the string is.

How does it work?

When glass is very hot, it expands and grows slightly larger. When it is suddenly made much cooler, the shape change happens too rapidly and the glass will crack because it is brittle. This is why, sometimes, if you have a cup that just recently had hot liquid in it, and you rinse if off with cold water, it cracks. This also happens when the temperature changes from cold to hot too. Do you notice how ice cracks when you put it in your room temperature water? The ice is also brittle and will crack with sudden temperature change.

Copyright 2011 Hawaii News Now. All rights reserved.