Why do tea bags split and leak leaf into the cup?

There are five usual reasons, and you can normally tell them apart by looking at the bag after you lift it out.

Fine sediment is normal

Tea bag paper has to let water through quickly, so it is porous. The smaller grades used in most everyday bags — fannings and dust — include particles fine enough to pass straight through. That is why a strong builder's brew often leaves a silt at the bottom of the mug and a pale ring on the china.

It is not a fault, and it is not a sign of cheap rubbish either: fannings brew fast and strong, which is exactly what a British mug of tea needs. Our guide to fannings and dust explains the grades.

If the sediment bothers you, pour slowly and leave the last centimetre in the pot, or brew loose leaf through a strainer.

Squeezing is the main cause of tears

The most common self-inflicted problem is pressing the bag against the side of the mug with a spoon and then dragging it up the wall of the cup. Wet paper is weak, the crimp is the weakest line, and it splits.

A gentler routine:

• Let the bag drain in the spoon rather than crushing it.
• Lift it with a spoon under the bag, not by the string.
• Never wind the string round the spoon and squeeze: that is the classic way to burst a bag.
• Take it out before you add milk, so you are not fishing in a pale mug.

Squeezing hard also pushes more tannin into the cup and makes the tea harsh, so there is a flavour reason too.

Seam failures and damaged boxes

A clean split along a sealed edge, on an unused bag, is a manufacturing fault. So is a box where the bags arrive already leaking.

If it happens across a whole box:

1. Stop using that box.
2. Keep the packaging, the batch or lot code and the best-before date.
3. Photograph an unused bag showing the fault.
4. Contact the retailer or the manufacturer with those details.

One burst bag out of eighty is bad luck. Several from one box is worth reporting.

Storage matters more than people think

Damp softens paper, and heat and steam near the kettle are the worst places to keep a box. Keep tea sealed, cool and dry — a cupboard away from the hob, not the shelf above the kettle. Old bags that have been open for a year go brittle as well as stale.

If it keeps happening, change the format

Whole-leaf bags such as Teapigs Everyday Brew use larger pieces and a roomier bag, so there is less dust to escape. Loose leaf removes the bag from the equation altogether: Yorkshire Tea Original Loose Leaf with a basket infuser or a pot and strainer gives you a clean cup and no seams to split. See loose leaf vs tea bags for the wider comparison.

Common questions

Is it safe to drink tea with leaf in it?
Loose bits of tea leaf are harmless — that is what loose leaf tea is. If the cup contains anything you cannot identify as tea, do not drink it and contact the seller.

Does sediment mean the bag has split?
Not on its own. Look at the bag: fine sediment with an intact bag is normal.

Are pyramid bags less likely to leak?
They give the leaf more room, but the mesh is what matters. Fine grades in a wide mesh will still shed.

Why does my tea have bits when my friend's doesn't?
Different grades, different brewing strength and different handling. A hard squeeze creates far more sediment than a gentle lift.

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