© Randal Oulton
Hard-Crack Stage is a cooking term meaning that a sugar syrup being heated has reached 149 – 154 C (300 – 310 F.)
It is a test of how hot a sugar syrup is, and of how much water is left in it. At this point of heating, the sugar concentration in the syrup is 99%.
You test by drizzling a small amount of the sugar syrup from a spoon into a cup of cold water. If the stage has been reached, the syrup will form threads. You may actually hear cracking and be alarmed that it’s the glass cracking, but it is the sugar.
Reaching this stage requires a lot of constant stirring, at first with a whisk to ensure blending, then a wooden spoon. Once the Hard-Crack Stage is reached, proceed with the recipe immediately before the sugar syrup turns to rock (it will also turn amber if heated more.) You have to work fast, as it begins to set immediately. But, you must be very careful with sugar syrup this hot.
The Hard-Crack Stage is called for in recipes for crunchy candies such as peanut brittle, barley sugar, etc.
The stages of cooking sugar syrup are:
High altitude: For every 300 metres (1,000 feet) that you are above sea level, subtract 1 degree C (2 degrees F) from the temperatures given in your candy recipe.