# Why is my toffee not hardening?

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## Summary

Toffee only sets hard if the syrup reaches the hard crack stage, 149 to 154°C. The usual reasons toffee stays soft or sticky, and how to avoid them.

## Description

Toffee is sugar, butter and sometimes treacle or syrup, boiled until almost all the water has gone. What decides whether it sets hard or stays soft is how far that boiling went: see how is toffee made?
The temperature was too low
Hard toffee is boiled to the hard crack stage, 149 to 154°C. As a sugar syrup boils, it loses water and gets hotter, and sweet makers name the stages by what a drop does when it cools: at soft crack the threads are just pliable, and at hard crack they are brittle.
Stop at soft crack, or below, and the toffee will bend, chew or stick to your teeth.
Testing without a thermometer
Before thermometers were cheap, cooks dropped a little syrup into cold water and checked it by hand, and the stage names come from that test. For hard crack, the syrup should form hard, brittle threads that snap. If they bend, keep boiling.
Damp air
Toffee is a non crystalline sweet: the sugar sets as a kind of glass rather than crystals. Low moisture sweets like this take up water from damp air, which can leave them rubbery, so toffee left in a damp kitchen can soften even if it was cooked properly. Humid weather can even stop a toffee apple's coating from setting at all: see how to make toffee apples
Cool and store toffee somewhere dry, and wrap pieces or keep them in an airtight tin: see why does seaside rock go soft?
Toffee or caramel?
Some recipes are meant to be soft. Caramel sweets add milk or cream and are finished at about 120°C, far below toffee, so they stay chewy on purpose: see what is the difference between toffee and caramel?

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