Why your backflow incense burner is not working

A backflow burner either works or it very obviously does not, and when it does not the smoke just climbs off the top of the cone like ordinary incense. There are four common causes and they are not equally likely. Work through them in this order and you will almost certainly find the problem in the first two.

It is nearly always the cones

A backflow cone has a hole bored up the middle. A standard incense cone is solid. The two look identical in a photograph, they are sold next to each other, and this is the single most common reason a burner does nothing at all.

Turn a cone over and look at the base. You should see a hole a few millimetres across. Push a cocktail stick in gently and on a backflow cone it will go most of the way up. If there is no hole, the smoke has nowhere to go but upwards and no burner will fix it, because cones bored through the middle are the only kind that work.

The second version of the same problem is cones that are genuinely backflow but the wrong size for the well. That one is covered further down.

Then look for air movement

The flow you are trying to see moves at a few centimetres a second and is driven by a density difference of well under one per cent. It is one of the weakest things happening in your room, and almost any air movement beats it.

Candidates, in rough order of how often they turn out to be the culprit: an open window or a window on the latch, a door open onto a hall or a stairwell, a radiator or underfloor heating below or beside the burner, a forced air vent, the exhaust from a laptop or a television, and you, walking past. A convection plume rising off a radiator will swallow the column completely.

Test it properly before you blame anything else. Shut the door, shut the window, turn off any fan and stand still for a minute. If the smoke falls once everything has stopped moving, you have your answer, and the fix is a different shelf rather than a different burner.

Then clean the channel

Incense smoke deposits two things: dry ash and a sticky brown condensate. The condensate is the problem. It builds up in the narrow part of the channel, collects ash on the way, and over a few dozen cones it can close the passage down to nothing.

Hold the burner up and look through the channel against a light. If no light comes through, it is blocked. A pipe cleaner, a cotton bud or a bent paper clip with a twist of kitchen paper on the end will clear most of it, and warm water with washing up liquid will take the rest, followed by a long rinse.

Then dry it completely, and give it longer than feels necessary. Ceramic holds water in a narrow channel for hours. Damp ceramic cools the smoke, condenses the moisture back out of it and reliably produces a burner that worked last month and does not work today. On a glazed ceramic burner the glaze makes the outside easy to wipe and does nothing whatsoever for the inside of the channel.

Then check how the cone is sitting

The bore in the cone has to line up with the hole in the well. If the cone is off centre, leaning, or sitting on a heap of old ash, the two never connect and the smoke takes the easy route upwards.

Empty the well before every cone. Ash is the usual culprit, and a small dam of it under the base is enough to seal the bore off completely. If the cone rattles about in the well it will drift as it burns. If it is too wide to sit down into the well at all, it is the wrong cone for that burner.

Check that the burner is level too, and that the surface under it is level. A tipped well makes the cone lean, and a leaning cone parts company with the hole.

Lighting it, which is the quiet failure

Hold the flame on the tip until the whole tip is glowing, not just one edge of it. Ten to twenty seconds is normal. Then blow the flame out and look at what is left: you want a continuous orange ring across the tip, not one bright spot.

A cone lit on one side only will burn down that side, smoke feebly and often go out altogether. If it has gone out there is no point relighting a charred tip, because the burnt material will not take. Break the dead part off or start a fresh cone.

Give it a minute or two before you decide it has failed. A cold channel full of still air does not produce a falling column straight away, and most burners need the channel to warm up and fill first.

Things that are not the problem

The burner being cheap is rarely the issue, because there is very little to a backflow burner: a well, a hole and a channel. What price mostly buys is the shape.

It does not need seasoning or breaking in. It makes no difference whether the cones are scented or plain, and the brand does not matter beyond whether the cones are bored and whether they fit. Humidity in the room has very little effect. Water sitting in the channel has a great deal.

One real exception: a cracked channel. If smoke leaks out of a crack in the body part way down, the column never builds and you get a vague haze instead. Hold the piece up to a bright light and look at the back of it.

Questions people actually ask

Why is the smoke from my backflow burner going up instead of down?

In most cases the cones are solid rather than bored through the middle, which leaves the smoke no route down into the burner. The next most likely cause is air movement in the room, which is strong enough to break the flow even when you cannot feel it.

How do I clean a backflow incense burner?

Clear the channel with a pipe cleaner or a cotton bud, then wash it with warm water and washing up liquid and rinse it thoroughly. Dry it completely before the next cone, because water left in the channel stops the smoke falling.

How long should a backflow burner take to start working?

A minute or two. The cone has to establish an even ember and the channel has to warm up and fill with smoke before a continuous column can form. If nothing has happened after three or four minutes, check the cone and the room rather than waiting.