Exploring the Science of Sugar Candy: Cooking Sugars

July, 2021




Rock sugar

What do:

Have in common?




Rock sugar


What do:

Have in common?

They all start out as a sugar syrup!

The sugar syrup is crucial for getting the right texture (e.g. crunchy, liquid, viscous)

What's sugar?

There are a lot of different types of sugars! All are small carbohydrates (mono- or disaccharides). Here, we're talking about sucrose, a disaccharide. It's your 'regular' cane or beet sugar.

Science Intermezzo

Sucrose molecule

Making a sugar syrup


Dissolve the sugar (sucrose)


Cook the sugar solution to the desired temperature

What happens when boiling sugar (sucrose)?

1. Water evaporates

Science Intermezzo

2. As a result, the concentration of sugar increases.

3. This causes the boiling point (temperature) to go up!

Why is this important?

The concentration of sugar in your syrup (and thus its boiling point) determines the consistency of your candy!

Let's look at some examples!

(these are cooked syrups that have been cooled back to room temperature)

105°C / 221°F

Appearance: Flows, it's a liquid

When to use?: Syrups (e.g. drizzle over a cake, to make jalebi candy)

112°C / 234°F

When to use?: in preserves, for kurma cookies

Appearance: Still flows, but clearly a lot thicker!

Don't have a thermometer?

Use the ice water test to test the consistency and concentration of your syrup:

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1. Prepare a jug of cold ice water

2. Take a sugar syrup sample

3. Drop in the ice water

4. Evaluate consistency of the sugar

Don't have a thermometer?

Use the following descriptors:

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– Thread: ≈102 – 113°C – Soft ball: ≈113 – 118°C – Firm ball: ≈118 – 121°C – Hard ball: ≈121 – 132°C – Soft crack: ≈132 – 149°C – Hard crack: ≈149 – 154°C

Keep in mind, a thermometer is more accurate (especially if you're not that experienced!)

115°C / 239°F

When to use?: fudge, fondants

Appearance: Again, a lot thicker! Doesn't really flow anymore

121°C / 250°F

When to use?: Italian meringue, marshmallow

Appearance: Forms thick long sheets when pulled

125°C / 257°F

When to use?: Nougat

Appearance: Very very viscous, hard to pull and stretch

135°C / 275°F

When to use?: Taffy, toffee, brittle

Appearance: Syrup doesn't flow anymore, it turned solid!

150°C / 302°F

When to use?: Honeycomb

Appearance: Syrup doesn't flow anymore, it turned solid!

≥160°C / 320°F

When to use?: Caramels

Appearance: Starting to turn brown!