Have you ever seen somebody get smashed on the head with a bottle in a film? Or thrown through a window? Have you ever seen a car being blown to smithereens on film? Then you have seen sugar glass in action.
Sugar glass is a film and theatre prop that looks and acts just like regular glass, but has a few distinct advantages: It is less hard, yet brittle, and when it breaks, it is less sharp.
For obvious reasons (insurance companies being the most obvious ones), you cannot run around smacking Nicolas Cage or John Travolta around the head with real glass bottles. What if you ruin their pretty faces for good? Enter Sugar Glass.
Sugar glass can be shaped (molded, actually) into just about any shape you want. This includes bottles, glasses, the glass that goes in spectacles, window panes, car windows, et cetera. Through varying the chemical production process, the sugar glass can get additional properties. There is sugar glass that is strong enough to walk on, but if you give it a short, sharp rap with something hard, it breaks into a thousand bits. There is sugar glass that can hold liquid (useful for staging bar brawls). And sugar glass can be made in just about any colour of the rainbow, to accomodate for sunglass colours, dark wine bottles etc.
In big budget hollywood films, the special effect pedants will actually travel to the factory that makes the real bottles (especially champagne bottles), and use the original molds to make the sugar glass models for breaking across actors' heads.
Making sugar glass yourself
The formulae for Hollywood versions of sugar glass is a well-guard industry secrets - the special effects people try new recipes and new mixes with different chemicals every time, and it is difficult to tell what your glass is made of. However, the times I have worked with professionally produced sugar glass, it has always tasted sweet-ish, so sugar is always an ingredient.
If you are running low on budget and cannot afford to buy specially produced sugar glass, there is a way of making your own. Be aware, though, that this sugar glass cannot handle heat or liquid:
What to do:
You will need a thermometer to measure the temperature of your mixture. Mix everything together and bring it to a boil (this happens at approximately 100 - 110 ° C, depending on the quality of the syrup). Leave it boiling for about 15 minutes, but try to keep the temperature stable.
Then, after the 15 minutes, let the temperature rise to 50 ° C hotter than its boiling temperature (if yours boiled at 105, cut it off at 155 ° C). This should take a little less than an hour, during which most of the water boils away, and the mixture becomes fairly thick.
When you hit your temperature, pour your sugar glass on a thick glass plate (if you are trying to make window pane) or a mold (if anything else) and let it cool off.
Voila! Sugar Glass!