Sugar Glass #SweetFailures

Written by: Jessica Roberts

HAPPY MOLE DAY, Everyone! Today we honor of the basic unit of chemistry, the beloved mole. From 6:02 a.m. until 6:02 p.m. chemists and chemistry lovers from around the world share their enthusiasm for our field through demonstrations, parties and other events in their communities. To mark this occasion, we at the Undergraduate Programs Office, returned to the secret laboratory to create some sugar glass!

Sugar glass is essentially sugar that has been melted down and re-formed into a transparent sheet. Because it is transparent and shatters like glass, Hollywood has used sugar glass in movie stunts for years. It looks and feels like real glass, but is a lot safer to break (and a lot more delicious!). Now filmmakers use a mixture of plastics instead to create a longer-lasting prop.

Dissolving the sugar solution on a hot plate.

To create the sugar glass we used table sugar, or sucrose, which is a disaccharide composed of glucose and fructose. We dissolved our ingredients in a 15:5:4 ratio of sugar to corn syrup to water and heated to 149°C. Corn syrup is comprised of different types of longer oligosaccharides, which helps to prevent large crystals from forming when the glass cools. If we didn’t add it, the glass would be opaque, not clear and not nearly as fun to break

Glass 3 To step it up a notch, we decided to make our glass fluorescent neon green which would glow under a black light. To give our glass the psychedelic treatment, we used tonic water instead of regular water and added neon green food coloring to the dissolved solution. Tonic water contains small amounts of quinine which fluoresces in the UV spectrum.

Glass 1After the sugar solution reached the magic temperature, it was poured out onto a greased cookie sheet to solidify. When the sucrose was dissolved in water and with heat, the bonds between the sugar molecules were separated, which can be reformed into a new shape while cooling. An important note: while it is important to oil your pan a little, doing too much will cause a slimy layer of oil on your candy glass to form, which hinders evaporation of the water as the glass cools. This causes the sheet to become bendy instead of brittle. We may or may not know from personal experience…. Also sugar is hydroscopic so it will absorb water molecules from the air the longer you leave it out. So it might be best to break it right after it cools.

Glass 2Despite our #sweetfailure in making high-quality sugar glass, we were able to produce some delicious glowing candy. We’d love to hear how you or your chapter celebrated Mole Day, so post in the comments below!

Materials:

  • 25 cups of sugar
  • 5 mL (5/12 cup) of light corn syrup
  • 9 mL (1/3 cup) of tonic water
  • Food coloring
  • Flavoring
  • Cookie sheet
  • Tin Foil
  • Non-stick spray
  • Thermometer
  • Mallet or hammer

Procedure:

  1. Line cookie sheet with tin foil and spray lightly with a non-stick spray.
  2. Bring to a boil the sugar, corn syrup and tonic water, stirring to dissolve.
  3. After it comes to a boil, add the food coloring and flavoring.
  4. Increase the temperature to 148.89°C (300°F) then remove from the heat.
  5. Pour the mixture onto the cookie sheet and allow to cool completely.
  6. Using a mallet or hammer, break the “glass”.
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