Why did my macarons crack, or come out with no feet?

Macarons are unforgiving because almost every variable is invisible until the shells are baked. The two you can actually control and observe are the batter consistency after macaronage and whether a skin has formed on the piped shells. The rest — meringue stability, oven behaviour, humidity — you manage by process rather than by looking. The drawing shows four shells in section, correct alongside hollow, footless and cracked, with the causes under each.

What you'll need

• Digital scales accurate to 1g
• A sieve for the almond and icing sugar
• An oven thermometer
• A piping bag and a plain nozzle

Step by step

1. Sieve the almonds and icing sugar together, twice.Lumps of ground almond will not smooth out and become the bumps that crack. Discard whatever will not go through rather than pressing it.
2. Make a stable meringue, and stop at stiff peaks.Under-whipped meringue cannot hold the batter up and gives footless shells. Over-whipped meringue is dry, breaks up during folding and contributes to hollows. Stiff, glossy, holding a peak that curls slightly at the tip.
3. Macaronage to the ribbon, and test it.Fold until the batter falls from the spatula in a thick continuous ribbon that sinks back into the surface within about half a minute. Under-mixed batter holds peaks and bakes lumpy; over-mixed batter is runny, spreads flat and produces no feet. This test decides more than any other step.
4. Pipe, then bang the tray hard.Drop the tray flat on the worktop several times, or bang it against your palm. This brings large air bubbles to the surface where you can pop them with a cocktail stick. Trapped bubbles are a direct cause of cracks.
5. Rest until a genuine skin has formed.Touch a shell lightly — your finger should come away clean and the surface should feel dry and matte. Twenty minutes in a dry kitchen, well over an hour in a humid one. This skin is what forces the expansion downwards into a foot instead of upwards through the top.
6. Verify the oven temperature.Most macaron recipes run at 140–150°C, and macarons are the bake that punishes oven error hardest. Too hot cracks them; too cool gives no feet. Use a thermometer, not the dial.
7. Bake on a doubled tray if the base browns.Two trays stacked, or an insulated sheet, moderates base heat. Silicone mats and parchment behave differently — pick one and stick to it while you are diagnosing.
8. Cool completely before lifting.Warm shells stick and tear their bases off. Let them cool on the tray entirely, then lift.

Tips

• Aged egg whites — separated and left covered in the fridge for a day or two, then brought to room temperature — whip to a more stable meringue. It is a real effect, not folklore.
• Weigh the egg white rather than counting eggs. Macaron ratios are tight enough that the difference between a medium and a large white matters.
• Italian meringue macarons, where hot syrup is beaten into the whites, are considerably more stable and more forgiving than the French method. Worth switching to if the French method keeps failing.
• Bake one small test tray first. It costs six shells and tells you whether the oven and the batter are right before you commit forty.

Common mistakes

• Skipping the rest because the shells look dry — Looking dry and being dry are different. Touch one. If anything transfers to your finger, the skin has not formed and it will crack.
• Trusting the oven dial — Ten degrees decides between cracked and correct. This is the one bake where an oven thermometer is not optional.

If it doesn't work