Cooking is often treated like fine art, but in fact, it’s more like a science. A medley of flavours, techniques, and temperatures are woven together to create culinary magic. There’s a bit of science in every kitchen, and sometimes it's a fascinating opportunity to watch complex chemical reactions at work. One such dish that embodies this is honeycomb candy.

Known by a variety of names - such as cinder toffee, seafoam, hokey pokey, crunchie, sponge toffee and many others - at its heart, it's a simple, sugar-based, airy, and very crunchy candy. Somewhere between toffee and brittle, it contains millions of tiny air bubbles that give it its unique texture – and the visual inspiration for its name. It’s also these bubbles that make it so interesting to eat because without them it would be a solid block of sugar.

With just three ingredients or sometimes even just two it's a quick fix for anyone craving a sweet treat. Sugar, sugar syrup – such as corn syrup, golden syrup or sometimes even honey – and baking soda are the three elements that make this tick. 

But even with so few ingredients, it can be a tricky dish to pull off. Get the sugar types or the measurements and it all collapses in seconds or it could go the opposite direction and become a sticky lump. Too much or too little baking soda and the delicate honeycomb pattern doesn’t even make an appearance. It’s true laboratory precision at work.

So let’s take a look at what happens at every stage of the honeycomb process.

Stage 1

The base of your flavours is bringing the mix of sugars to an extremely high temperature. If you’re using your ingredients right, there should be a solution of sucrose, glucose, and fructose as well as other larger carbohydrates and water. 

When they begin to boil in water they will all be dissolving into the liquid and as it heats towards 100°C, the water content will be slowly burnt away and the sugar will become more concentrated, and the boiling point will increase. Because of this, the sugar will continue to heat beyond 100°C.

The aim is to concentrate that sure so much that when it cools again, the molecules have nowhere to move around freely anymore and they form a glassy, brittle texture. And the only way to be sure the right concentration has been reached is to keep track of the temperature.

Stage 2

Once all the moisture has been removed, it’s time to aerate with baking soda. The chemical name for baking soda is sodium bicarbonate (NaHCO3). When the bicarbonate reacts with an acid in the sugars, it splits to form carbon dioxide gas which is what is formed throughout the honeycomb to expand the sugar solution. The higher the temperature, the quicker this happens.

Here’s the chemical formula for the reaction

HCO3– + H+ ↔ H2CO3 –> H2O + CO2

The caramelisation of the sugar also happens at this stage, and it only occurs when sugar is heated above 150°C. However, the process is sped up when the pH is more acidic or more alkaline than usual. The addition of alkaline baking soda helps it caramelise quicker.

The colour will also become lighter because the formation of all the air bubbles diffuses the light and as the solid reflects light differently, it will appear more yellow.

Stage 3

The last stage is the most straightforward but can also prove crucial. It needs to cool at the perfect speed to ensure that the gas doesn’t escape from the mixture. That’s why the depth of the final container must be perfect so that it all cools evenly and the centre doesn’t end up soft. 

If you think you’re ready to take on this kitchen experiment, here’s a foolproof recipe to guide you through it.


    100 g coarse sugar

    45 g corn syrup (golden syrup or honey can also be used)

    25 g water (exact quantity not important, adding more will only increase the cooking time)

    ½ tsp baking soda


    Prepare a heat-resistant tray/cake tin and cover it with parchment paper.

    Mix the sugar and corn syrup in a pan and add the water.

    Bring the mixture to a boil and ensure that all the sugar crystals have dissolved.

    Continue cooking the sugars until they are 150°C and starting to brown slightly.

    Take the mixture off the heat and immediately mix in all the baking soda.

    Immediately pour onto the heat-resistant surface and leave to cool.

    Once it's cooled down, break into shards and store in an airtight container.