Video:3 Tips for Growing Sugar Crystalswith Anne Marie Helmenstine
Making sugar crystals, or rock candy, is a fun and simple science experiment. Learn how to make sugar crystals at home with these tips.See Transcript
Transcript:3 Tips for Growing Sugar CrystalsSugar crystals or rock candy are among the safest crystals to grow - you can eat them.
Make Sugar Crystal with a Saturated SolutionThe most common method to grow sugar crystals involves making a saturated sugar solution, hanging a rough string in the liquid, and waiting for evaporation to concentrate the solution to the point where crystals start to form on the string. The saturated solution is made by adding sugar to hot water until it starts to accumulate in the bottom of the container and using the liquid as the crystal growing solution. This method tends to produce crystals over a week or two.
Tips to Help Make Sugar CrystalsIt will not work if you live someplace where the air is so humid that evaporation is very slow or if you place the container in a location where the temperature fluctuates, like a sunny window sill, so that the sugar stays in solution. If this method does not work, here are 3 tips to make this work:
Grow a Seed CrystalBreak a seed crystal from a piece of rock candy or sugar crystal. Use a simple knot to tie the seed crystal onto some nylon line. Suspend the crystal in the solution, till completely covered, yet not touching the sides or bottom of the container.
Supersaturate Your Crystal SolutionTo boiling water, stir in more sugar than will dissolve. Pour the solution through a coffee filter so no undissolved sugar remains in the solution. You can use this solution as-is or you can let it evaporate for a day or so, until you see crystals start to form on the container. If you choose to evaporate off some of the liquid, reheat it and filter it before introducing the seed crystal.
Cool the Crystal Solution SlowlySugar becomes much less soluble as the temperature falls from boiling to room temperature or refrigerator temperature. The 'trick' is to allow the solution to cool slowly. You could set the crystal growing container inside a pot of near-boiling water. Either seal the container so that no water gets in or else make sure the sides of the crystal container are suitably tall.
Let the whole setup slowly drop down to room temperature. Sugar crystals grow slowly so while you might see growth within a couple of hours, it may take a few days to be visible. If you suspend a seed crystal in a sufficiently saturated solution, you may get crystal growth over a few hours by controlling the cooling of the solution.
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