Rock Candy

Dissolve sugar into hot water until it forms a supersaturated solution, then suspend sugar-coated sticks in jars to grow edible sugar crystals over several days. Color or flavor can be added to make decorative, tasty rock candy.

1. Shape or cut wooden skewers so they fit your jars without touching the bottom; clip a clothespin to each skewer so it can hang centered.
2. Wet each skewer and roll it in granulated sugar to make a seed layer; set aside to dry completely.
3. Heat water in a saucepan and stir in sugar until it dissolves; continue adding sugar a little at a time until no more dissolves and the liquid looks slightly cloudy (about a 3:1 sugar to water ratio by volume).
4. Optional: Add a few drops of food coloring and a small amount of candy flavoring; bring just to a gentle simmer, then remove from heat.
5. Let the syrup cool until it is hot but not boiling to reduce thermal shock to glass.
6. Pour the hot syrup into clean, heat-safe jars, one color per jar if making multiple colors.
7. Lower a fully dried, sugar-coated skewer into each jar and use the clothespin to keep it suspended in the center without touching sides or bottom.
8. Place jars where they can sit undisturbed; loosely cover tops with paper to keep out dust.
9. Observe crystal growth daily; if a surface crust forms, gently break it with a clean utensil so crystals can continue to grow on the stick.
10. After 5–7 days, lift sticks out, let excess syrup drip off, and place them on a clean surface to dry before eating.

Rock Candy Experiment - Emily's Science Lab:

Watchable by stmartins.sa.edu.au. Make Your Own Rock Candy! | The Science of Cooking! - SciShow Kids:

📄 Rock Candy Experiment - Play Learn Grow: https://www.growingajeweledrose.com/2015/02/rock-candy-experiment.html

• Compare different starting sugar concentrations (2:1 vs 3:1) and record how growth rate and crystal size change.
• Test food coloring in the solution versus painting finished crystals lightly with gel color.
• Try cotton string tied to a pencil instead of a skewer and compare crystal coverage.
• Grow larger crystals by transferring sticks to a fresh hot supersaturated solution after several days.

• Hot syrup can cause burns; adults should handle heating and pouring, and use heat-safe jars on a stable surface.
• Keep jars out of reach while hot; allow to cool before children observe closely.
• Use only food-safe containers, utensils, colorings, and flavorings if the candy will be eaten.
• Do not handle sticks with bare hands after dipping if you intend to eat them; use clean tools and good hygiene.
• Cover jars to prevent contamination by dust or insects; discard any batch that shows mold or off smells.

• Why do crystals grow as the solution cools and sits? (The hot solution holds more dissolved sugar; as it cools and evaporates, it becomes supersaturated and sugar deposits as crystals.)
• Why coat the stick with sugar first? (The rough sugar layer provides nucleation sites so crystals start on the stick instead of the jar walls.)
• What controls crystal size? (Higher supersaturation and faster cooling favor many small crystals; slower cooling and stable conditions favor fewer, larger crystals.)
• What happens if the stick touches the jar wall or bottom? (Crystals can bridge to the glass, fusing the stick in place and reducing even growth.)
• Why is the 3:1 ratio recommended? (It reliably achieves supersaturation at kitchen temperatures, promoting steady crystal growth without needing extreme evaporation.)