Tunneling

The defect that wastes the most wax and generates the most complaints, and the one that is decided in the first hour of the candle's life.

A hole down the middle

The wick burns a narrow shaft down the center and leaves a wall of unmelted wax against the glass.

The customer gets perhaps half the candle they paid for, and towards the end the flame sits down a hole where it cannot draw air, gutters and drowns.

The first burn writes it

Wax has memory. Whatever diameter the melt pool reaches on the first burn is roughly the diameter it will reach every time after.

So a candle burned for an hour the first time will tunnel for the rest of its life even if every subsequent burn is four hours.

That is why "burn until the melt pool reaches the edge on the first burn" is on every candle care card in the category.

Why it is not the customer

A candle that only avoids tunneling if burned perfectly is under-wicked.

The test is four hours: if a full melt pool has not reached the wall by then, the wick is too small and no instruction fixes it.

Blaming the burn habit is the commonest way a maker avoids re-testing, and the complaints continue.

Fixing it

Go up one wick size and retest the full burn.

If going up causes soot or an over-deep pool, the wick series or the fragrance load is wrong rather than the size.

Check the vessel too: a wide vessel with one wick is the usual structural cause, and two smaller wicks often beat one large one.

And put the first-burn instruction on the care card anyway. It is true, it helps, and it is not a substitute for the right wick.

References