How to Brew Coffee with a Vietnamese Phin Filter

If Vietnamese coffee had a symbol, it would be the phin. This humble metal filter, small enough to fit in your palm, brews the strong, chocolatey coffee that fuels the whole country. It costs very little, needs no electricity or paper filters, and turns coffee-making into a calm little ritual.

The phin is simple, but there's an art to getting it right. In this guide we'll explain how it works, what you need, and exactly how to brew a great cup, whether you like it black, with condensed milk or poured over ice.

What is a phin filter?

A phin (pronounced roughly "fin") is a single-cup drip brewer, usually made of aluminium or stainless steel. It has four parts:

• The base plate, which rests on top of your cup or glass and has small holes in the centre.
• The brew chamber, a small cylinder that holds the ground coffee and water. It's often attached to the base plate.
• The press, a perforated disc that sits on top of the grounds to keep them in place. Some press down by gravity, others screw into the chamber.
• The lid, which keeps the heat in while the coffee drips, and doubles as a tray for the phin afterwards.

Water passes slowly through the coffee and out of the holes at the bottom, producing a small, concentrated cup. Because the filter is metal rather than paper, more of the coffee's natural oils make it into your cup, giving phin coffee its rich, full body.

What you'll need

• A phin filter
• 20 g of ground coffee (about 2 to 3 tablespoons)
• Around 100 to 120 ml of water, just off the boil
• A heatproof glass or cup
• Sweetened condensed milk and ice, if you want to make cà phê sữa đá

The right grind and ratio

Grind size is the most important variable. Aim for a medium-coarse grind, a little finer than you'd use for a French press and coarser than espresso. It should feel like coarse sand. If the grind is too fine, the coffee will clog and drip painfully slowly; too coarse, and water will rush through, leaving you with a weak, sour cup. Many Vietnamese coffees are sold pre-ground specifically for the phin, which is a good place to start.

The ratio is roughly 1 part coffee to 5 or 6 parts water, so around 20 g of coffee for 100 to 120 ml of water. That produces a strong concentrate designed to be sipped slowly or mixed with milk and ice.

Water temperature should be hot but not boiling, around 90 to 96°C. Leave the kettle to rest for about 30 seconds after it boils.

Step-by-step: brewing with a phin

1. Prepare your glass. If you're making milk coffee, add 1 to 2 tablespoons of condensed milk to the bottom of the glass first.
2. Preheat the phin. Rinse the filter with hot water. This keeps the brew from cooling too quickly.
3. Add the coffee. Spoon the grounds into the chamber and give it a gentle shake to level the bed.
4. Insert the press. Place the press on top of the coffee. If yours screws in, tighten it gently, then loosen it about half a turn. Too tight and the coffee won't drip.
5. Bloom. Pour in about 20 ml of hot water, just enough to wet the grounds, and wait 30 to 45 seconds. You'll see the coffee swell as it releases gas, which helps it brew evenly.
6. Fill and cover. Fill the chamber to the top with hot water and put the lid on.
7. Wait. The coffee should drip steadily for around four to five minutes. If it's much faster or slower, adjust next time (see below).
8. Finish. When the dripping stops, lift the phin off and rest it on its upturned lid. Stir and enjoy.

How to make cà phê sữa đá

Vietnam's famous iced milk coffee is simply phin coffee brewed over condensed milk, then poured over ice. Once the drip is complete, stir the coffee and condensed milk together until smooth, then pour the mixture into a tall glass filled with ice. Stir again and wait a moment for it to chill. Adjust the condensed milk to taste: Vietnamese cafés tend to be generous.

For a black iced coffee, known as cà phê đen đá, skip the milk and add a little sugar if you like.

Troubleshooting your phin

The coffee drips too fast. Your grind is probably too coarse, or the press is too loose. Try a slightly finer grind or press a little more firmly.

The coffee barely drips at all. The grind may be too fine, or the press screwed in too tightly. Loosen the press slightly or tap the side of the chamber gently to get things moving.

It tastes bitter or harsh. The brew may be running too long, or the water is too hot. Try a coarser grind and let the kettle cool a little longer.

It tastes weak or sour. Use a little more coffee, a finer grind, or make sure you're blooming the grounds before filling the chamber.

Choosing coffee for your phin

Traditionally, phin coffee is made with dark-roasted Robusta or a Robusta-heavy blend. Its bold, chocolatey bitterness and heavy body are exactly what you want under condensed milk. If you prefer your coffee black, try a medium-roast Arabica for a lighter, fruitier cup. Whichever you choose, fresher is better: buy small amounts and store your coffee in an airtight container away from heat and light.

Caring for your phin

A phin is almost indestructible, but a little care keeps it brewing well. Rinse it with hot water after each use and let it dry completely. Avoid harsh scrubbing, and if your phin is aluminium, wash it by hand rather than in the dishwasher, which can discolour the metal. Every so often, check that the holes in the base and press aren't blocked by fine coffee particles.

The phin rewards patience. Those few minutes of waiting are part of the pleasure, a small pause before the day speeds up. Brew one tomorrow morning, sit somewhere sunny, and let the coffee take its time.