Vietnamese phin filter

The four pieces, from the glass upwards

Widely documented

Gravity insert or screw-down

Tendency, not a guarantee

Gravity insert

The disc simply rests on the coffee under its own weight. It is quick to use and consistent, since there is no setting to get wrong. This is the commoner type.

Screw-down insert

The disc threads onto a post in the chamber and can be tightened to compress the coffee. That gives control over drip speed, and a way to choke the filter completely if overdone.

Size and metal

Widely documented

Phins are sold by capacity, from single small servings up to sizes meant for sharing. The traditional drink is short and strong, served over sweetened condensed milk or ice, so a small phin is the usual choice. A larger one makes a longer black coffee or two small servings.

Stainless steel is durable and does not dent easily; one maker describes its steel phin as dishwasher safe, and yours may differ. Aluminium is lighter and cheaper and is the traditional material in many households; it marks more readily and is better washed by hand. The metal has little effect on the coffee compared with the grind.

What it needs to work well

CoffeeHQ explanation

The holes in the base are small but not fine enough to stop powder. A grind that is too fine clogs them and also falls through into the cup; one that is too coarse lets the water race through. Advice on where to start differs. One maker of phin filters recommends a grind between pour-over and espresso, about where a moka pot sits; many other descriptions say medium-coarse. The holes are not the same size from one phin to another, so the drip is the better guide: that maker suggests the first drop should fall within about two minutes and the last at around five or six. Faster than that, grind finer; much slower, grind coarser.

The same maker points to two causes of a stalled filter that have nothing to do with the grind. A phin that is still wet from washing can have water sitting in its holes, so dry it before use. And very fresh coffee gives off gas that can hold the water up; wetting the grounds and waiting most of a minute before filling lets it escape.

A heatproof glass lets you watch the drip and see when it has finished. Preheating the phin and the glass with hot water helps, because a small metal brewer loses heat quickly over a brew that takes several minutes.

If it will not drip properly

CoffeeHQ explanation

Nothing comes through, or only an occasional drop

Usually because: The grind is too fine, or a screw-down insert has been tightened too far.

Change first: Loosen the insert first; if that does not help, grind coarser next time.

It is finished in a minute or two and tastes thin

Usually because: The grind is too coarse, so the water is not held in contact with the coffee.

Change first: Grind a little finer.

Gritty sediment in the glass

Usually because: Fine particles are passing through the base holes.

Change first: Grind slightly coarser and avoid stirring the bed once water is in.

Grounds float and the bed is uneven

Usually because: Water was poured in fast before the coffee had been wetted.

Change first: Add a small amount of water first, wait about half a minute, then fill.

What to do next

• How to brew with a phin — The method in full, including the bloom and the usual proportions.
• Vietnamese cà phê phin — The tradition the filter belongs to, and how the drink is served.
• Grind size guide — Where a phin grind sits relative to other brewing methods.
• Become a barista — A structured programme from dose and grind through milk, drinks and maintenance.