Michelle 'Nanogirl' Dickinson has just released The Kitchen Science Cookbook. She talks us through the process of making rock candy and hokey pokey – two simple recipes that use the science of sugar.
Sugar has a really bad reputation right now, but it's an important molecule, not bad as a small part of a balanced diet and fun to do science with, Michelle says.
The speed at which you cool it down will change how its molecules form and behave – i.e whether they become brittle, soft, transparent or opaque.
Rock candy is see-through and with jagged edges, while hokey pokey is brittle, bubbly and opaque.
"Hokey pokey is great for science because the kids can break it apart and look inside it at the size of the holes, they can feel the texture of it and compare it to the rock candy."
You need a bit of patience with this recipe as it the crystals grow over one or two weeks. The longer you leave them the bigger they'll grow, Michelle says.
"It's so cool, it's so pretty, too."
How to make rock candy
Boil water in a pan.
Add castor sugar and keep stirring until it goes cloudy (the amount of sugar you need will depend on the temperature of the water, how fast you're stirring and the pH level of your water). "As you heat it up you apply more energy, and as you apply more energy more sugar can dissolve in it."
- Once it's cloudy, the mixture has become a 'supersaturated solution' (which just means lots of sugar has dissolved).
- Pour this into a clean glass (without too many scratches on it – if the glass is dirty it will form crystals there).
- Wet a wooden skewer and roll it in sugar, then dip the skewer into the centre of the glass sitting about 1cm from the bottom and hold it there with a clothes peg lying across the top of the glass.
- Put the glass on the table or in the fridge – somewhere it won't be knocked.
- Over the next few days, the sugar comes out of the solution and will stick to the skewer and start to form sugar crystals: "Sugar will naturally go there 'cause it's a lower energy point to start bonding with."
Hokey pokey (honeycomb)
Hokey pokey is easy and fun to make, Michelle says.
Made it alongside instant ice cream and you can have homemade hokey pokey ice cream in under 10 minutes.
How to make hokey pokey
- Warm 1 and 1/2 cups of white sugar and ½ cup of honey in a saucepan over medium heat for 3 minutes.
- As soon as you see the colour change to an autumny darker brown, switch off the heat and sift in 1 tablespoon of baking soda.
- Stir frantically and it will foam up.
- Quickly pour it into a lined baking tray so it can cool quickly and solidify over a large surface.