Keyhole fire: separating flames and cooking coals

Wood burns in two phases. First it gives off gases that burn with bright, restless flames. After that, charcoal remains, which glows without big flames and radiates heat evenly. For cooking, the second phase is much better: the heat is steady, predictable and makes hardly any soot.

In a keyhole fire both phases run side by side. Wood is added continuously in the round burning area, and new coals keep forming there. You push these coals into the narrow cooking area as needed. If the pot needs more heat, you fetch more coals; if it only needs to keep warm, you take some away.

The most important thing is patience. Coals take time to form. If you cook too early, you only have a few glowing bits and get impatient. Hardwood or simply enough fuel wood gives the best coals. So allow time before the food goes on the grate.

A stable pot support is just as important. A grate or flat, dry stones on each side of the narrow part carry the pot or pan. If something wobbles, boiling water can slop over. If possible, lay the narrow part across the wind so that smoke and sparks from the burning area do not drift over your cooking spot.

Do not use stones from streams or wet ground. Water can be trapped inside them, which turns to steam in the heat and can make the stone burst – with sharp, hot fragments.

The keyhole fire suits groups and longer camps where people cook and warm themselves at the same fire for hours. Pan and grill dishes turn out much better over coals than over flames.

For quickly boiling water it is too cumbersome – a stove is much faster. It is unsuitable in dry and windy conditions, and it needs a larger fire site and more wood. Use only permitted, existing fire sites with mineral soil or a stone ring. In places where no traces should be left, do not create a new, large fire site.

Coals in the cooking area are often hard to see in daylight because they are covered with grey ash. They are still very hot. Keep children away, do not step over the cooking area and wear sturdy shoes. Cool burns immediately with cool, not ice-cold, running water; for large or deep burns, burns to the face or hands and burns in children, call the local emergency number (112 in the EU).

At the end, both areas must be completely extinguished – not just the one that still has flames. Pour on plenty of water, stir, pour again and check with the back of your hand from a little distance whether any heat is still rising. Only when everything is cold may you leave. And as always, beforehand: check local rules and wildfire danger.

The keyhole shape is widespread among scout and outdoor groups. Its basic idea applies to any fire, though: if you cook on coals rather than flames, you cook more calmly, more safely and with less soot on the pot.

You can use this at an ordinary round fire site too, by pushing some of the coals to the edge and cooking there while wood keeps burning in the middle.