Why did my caramel crystallise?

Caramel is molten sugar held in an unstable state, and it is looking for an excuse to return to crystals. Everything about the technique is aimed at denying it one.

Safety

Step by step

1. Understand the mechanism.Dissolved sugar wants to re-form crystals. A single undissolved grain, or one stuck to the pan side, seeds the process, and it propagates through the whole pan in seconds.
2. Choose wet or dry deliberately.Wet caramel dissolves the sugar in water first and is far more forgiving for beginners. Dry caramel melts sugar alone — faster, but it burns and crystallises much more readily.
3. Dissolve fully before it boils.For a wet caramel, stir over gentle heat until you cannot feel any grains and the syrup is clear. Undissolved sugar at boiling point is the most common seed.
4. Stop stirring once it boils.This is the rule people break. Agitation encourages crystals to form. Swirl the pan gently if you need to even the colour, but put the spoon down.
5. Wash the sides down.A pastry brush dipped in water, run round the inside of the pan above the syrup. Sugar splashed up the side dries into crystals that fall back in.
6. Add an interfering agent.A squeeze of lemon juice, a pinch of cream of tartar, or a spoonful of glucose or golden syrup. These break some sucrose into simpler sugars that physically get in the way of crystal formation.
7. Use a heavy pan.Thin pans have hot spots that burn one area while another lags. A heavy-based pan gives even heat, which matters more here than in almost any other cooking.
8. Keep the pan spotless.Any speck of debris acts as a seed. Clean pan, clean utensils, and do not use the spoon you stirred with earlier.
9. Judge by colour, not time.Pale gold to deep amber happens fast and continues off the heat. Take it off slightly before the colour you want, because residual heat carries it further.
10. Warm anything you add.Cold cream into hot caramel spits violently and can seize it. Warm the cream, add it slowly, and stand back.
11. Rescue it if it does crystallise.Add water — roughly a quarter of the original sugar volume — and heat gently, stirring, until every crystal dissolves again. Then proceed as before, without stirring.
12. Know when it is burnt rather than grainy.Crystallised caramel is grainy but salvageable. Burnt caramel is acrid and black-flecked, and no amount of water fixes the taste. Start again.

Tips

• Put the spoon down once it boils. Stirring is the single most common cause.
• A wet pastry brush round the pan sides costs seconds and removes the seeds that cause most failures.
• Grainy caramel is rescuable — add water and re-melt. Burnt caramel is not.

Common mistakes

• Stirring boiling sugar syrup — Agitation encourages crystal formation, and one crystal seeds the entire pan within seconds.
• Adding cold cream to hot caramel — It spits violently, which is a burn risk, and the sudden cooling can seize the caramel into a solid lump.

If it doesn't work