Why Won’t My Fire
Burn Properly?

The quick diagnosis

Before the detail, here is the honest distribution. Of the fires we get asked about, the cause breaks down roughly like this:

People almost always suspect the stove and almost never suspect the wood. It is nearly always the wood.

It will not light

A cold stove and a cold flue have no draught. Until the flue warms up, nothing is pulling air through the fire, so the fire has to be small, fierce and dry enough to make its own heat fast.

• Start smaller than feels sensible. A firelighter, a good handful of kindling, then thin splits. Full logs go on when there are flames, not before.
• All the air open. Every vent, wide open, for the first fifteen to twenty minutes. You can close it down later; you cannot recover a fire you starved at the start.
• Top-down works better. Big logs at the bottom, kindling above, firelighter on top. It burns downwards, warms the flue early and smokes far less than the traditional way up.
• Warm the flue if it is stubborn. On a cold, still day, hold a lit firelighter or a rolled newspaper up inside the flue for thirty seconds to start the draught.

The glass goes black

Below roughly 260°C the smoke coming off the wood does not ignite. Those unburnt particles have to land somewhere, and the coolest surface in the firebox is the glass. So black glass is always the same message: the fire is not burning hot enough.

Two causes, usually together. Wet wood, which spends its energy boiling water instead of making heat. And the air closed down too far, too early, which starves the fire and drops the temperature.

The airwash system on a modern stove — the slot that sweeps air down the inside of the glass — only works when the fire is hot enough to drive it. Turning the air down does not just slow the fire; it switches off the thing that keeps the glass clear.

Smoke comes into the room

This one is worth taking seriously, because it means the flue is not pulling. Common causes, in the order worth checking:

• Cold flue, no draught yet. Most common by far, and it settles once the fire is established. Warm the flue first as described above.
• The room is sealed. Modern draught-proofing, a closed trickle vent, an extractor fan running in the kitchen. The fire needs air from somewhere. Crack a window and see if it stops.
• Opening the door too fast mid-burn. Open it a crack, wait a couple of seconds, then swing it.
• The flue needs sweeping. If it has been more than a year, this is your answer.
• Wind conditions. Some chimneys down-draught in certain winds. A cowl fixes it.

It burns but gives no heat

Almost always moisture. Every litre of water in a log must be boiled off before that log gives useful heat, and it takes heat from your fire to do it. Wood at 40% moisture can lose a very large share of its energy to that before any of it reaches the room.

The secondary cause is species. Birch and softwood are light timbers, so a firebox full of them holds much less energy than the same firebox full of oak or ash. If your fire burns brightly, looks lovely and does not warm the room, look at what is in it — see which wood burns best.

The third possibility is an oversized stove run permanently shut down. A 12kW stove in a room that needs 5kW gets damped right down to be bearable, and a damped stove is an inefficient stove.

It burns through too fast

The opposite complaint, and usually the opposite cause.

• Too much air. Once there is a solid bed of embers, the air can come down. Not off — down.
• The wood is too light. Birch and sycamore burn quickly by nature. For overnight burning you want dense hardwood or ash.
• Logs too small. Several small logs have far more surface area than one big one and burn correspondingly faster. For a long burn, one or two large splits on a good ember bed beats a firebox full of kindling-sized pieces.
• The flue is over-drawing. A very tall or very exposed chimney can pull too hard. A flue damper is the fix, fitted by a stove engineer.