Why Meringue Turns Yellow: 120 °C Is the Line

120 °C. That is the line. Below it, meringue dries and stays white;
above it, the sugar starts to caramelise, and caramel is brown. Nothing has gone wrong with
your egg whites — the oven was simply on the wrong side of one number.

Why that temperature specifically

Meringue is dried, not baked. The job of the oven is to drive water out slowly while the
protein holds its shape. Sugar begins colouring well before it begins burning,
and 120 °C is roughly where that starts to show over a two-hour bake.

Below the line: 90–110 °C

Pure white and crisp all the way through, but slow — two and a half to three
hours for standard nests. If your oven will not go that low, prop the door open with
a wooden spoon.

At the line: 110–120 °C

Slightly cream-coloured with a marshmallow centre, in an hour and a half to two.
Many people prefer this and are not chasing white at all.

Above the line: 130 °C and up

Golden and chewy in about an hour. A perfectly good dessert — just not a white meringue,
and no technique will make it one.

Result	Oven	Time
Pure white, crisp through	90–100 °C	2.5–3 h
Slightly cream, soft centre	110–120 °C	1.5–2 h
Golden, chewy	130 °C+	1–1.5 h

When you are on the wrong side without knowing

The oven runs hot. Most domestic ovens are 10–20 degrees off,
and at these temperatures that is the entire margin. An oven thermometer settles it.

Fan versus static. A fan oven dries faster but its effective temperature is
higher — drop the setting by about 20 degrees.

When the number is not the problem at all

Unrefined or golden caster sugar produces a cream-coloured meringue at any temperature.
For a white result you need plain white caster sugar.

And after the oven

Turn it off and leave the meringue inside with the door ajar until completely cold.
Pulling it into a warm kitchen causes cracking and, in a humid room,
weeping.