An even or a contrasting yolk: ice bath or air cooling
A yolk is never the same temperature all through. Heat comes in from the outside, so the edge of the yolk always gets hotter than its centre, and how much hotter depends mostly on how you cool the egg. That choice decides whether you get an even yolk or a firm rim around a soft centre.
How much hotter the edge gets
A medium egg (58 g) cooked to a jammy yolk at sea level, so that the centre of the yolk peaks at 66 °C in every case. The edge is where the yolk meets the white, at its widest point.
| Egg starts at | Cooled in | Boil for (58 g) | Yolk edge | Hotter than the centre by |
|---|---|---|---|---|
| Room temperature | Air | 4:34 | 79 °C | 13 °C |
| Fridge | Air | 5:39 | 79 °C | 13 °C |
| Room temperature | Water | 7:12 | 87 °C | 21 °C |
| Fridge | Water | 8:22 | 87 °C | 21 °C |
| Room temperature | Ice bath | 7:26 | 87 °C | 21 °C |
| Fridge | Ice bath | 8:36 | 87 °C | 21 °C |
An egg cooled in the air spends less time in the pot and gets much of its cooking from the heat that spreads inwards on the counter, which evens the yolk out: its edge ends up only about 13 °C hotter than its centre. An egg cooled in an ice bath gets most of its cooking in the boiling water, which drives the outside of the yolk much further ahead: about 21 °C. Whether the egg started in the fridge or at room temperature makes almost no difference.
Choose by taste
Neither is better; it is a matter of taste. Yolk starts to set around 70 °C and is firm above 77 °C, so:
- For a more even yolk, cool in the air. The edge still sets, but the yolk changes more gently from the centre outwards.
- For contrast, cool in an ice bath. A firm rim around a soft, jammy centre: the classic ramen egg.
Whichever you choose, the calculator adjusts the boiling time so the centre still lands where you want it: an egg cooled in the air comes out of the pot much earlier.
Open the calculator and choose how you will cool the egg.