Learn how to make honeycomb, the most delicious science experiment you will ever attempt. It is is a combination of a few different chemical reactions – most notably caramelisation and an acid-base reaction. Nothing really comes close to honeycomb for being tasty, impressive and dangerous!
Use this foaming, sweet napalm to make your own violet crumble bars, serve as a petit-four or bake into muffins. You can even stir it into some vanilla ice cream to make a hokey-pokey.
Measure out your ingredients and line a baking tray with baking paper.
Add the sugar, syrup, and a little bit of water to a high sided pan. Place over a medium heat to dissolve the sugar.
Bring the sugar to a boil and cook until the toffee reaches a light caramel colour. This is about 150 degrees on a candy thermometer.
Carefully tip the bicarb into the toffee and whisk quickly to aerate. It will foam up considerably, so don’t let it touch you. This stuff could be weaponised.
Pour the honeycomb into the tin and let cool for 30 minutess, or until set.
Your tin should not be too deep, and do not take your toffee too far, as the honeycomb will keep cooking for a while after and may burn itself.
Now, what just happened?!
Firstly, you’ve dissolved sugar into water. If you start with a large volume of sugar and a smaller volume of water by ratio the sugar may not completely dissolve at first. But it will eventually once the water reaches boiling point. So the good news is we’re not breaking the laws of thermodymamics. The bad news is we’re not breaking the laws of thermodynamics. So we won’t be able to collect the Nobel Prize for a honeycomb flavoured perpetual-motion machine.
Once your sugar solution is boiling water converts to gas. So far, so year 7 science. As the water evaporates your sugar solution is becoming more concentrated. As the sugar concentrates it requires a higher temperature to continue boiling.
This is why your sugar is now creeping above 100 degrees and becoming a little bit excited.
Once the sugar reaches a certain point – 160 generally – the sucrose and glucose start decomposing and begin to burn. This is when your caramel starts to get those nice brown colours and delicious aromas. But if you get distracted for a nanosecond it will burn black.
The moisture content of the solution also dictates what consistency it will be when it cools. Soft ball at is at 115 degrees, soft crack at 130, hard crack at 150, etc.
If caramelisation happens at 160, why are we only taking it to 150?
The syrup and the bi-carb when we add it act as an impurity, lowering the caramelisation temperature. Also, the temperature will continue to rise off the heat, after the bi-carb is added to it will reach 160 in the pan.
How does the bi-carb work?
The bi-carb leavens the caramel, causing it to foam because it is a relatively unstable alkaline which reacts quite violently to the intense heat in the caramel. Once the bi carb hits the caramel it starts releasing carbon dioxide, the mixture foams up rapidly and then the rapidly cooling toffee sets to hard crack, trapping the gas bubbles.
So, there you have it, the delicious science of honeycomb.
Look for a future post on how to scientifically scrub the set caramel out of the saucepan.