Which Grind Size Is Best For Brewing Vietnamese Coffee/Phin?

Got a Vietnamese Phin filter but the results aren’t quite what you expected? The grind size has a big impact on the final result so let’s figure out what grind size is best to brew Vietnamese coffee with a Phin.

A medium grind size is the best for brewing Vietnamese coffee in a Phin. This way brew time and extraction are good while no grounds get in the cup. A medium-fine grind is OK and will brew a stronger cup of coffee at the expense of some residue. Pre-ground coffee for drip filters will work.

For more information on all the details and how to prevent your Phin from dripping too fast, keep reading below.

Grind size for Phin

So let’s assume you’re going to make coffee with a Phin. That will be the most authentic way to make Vietnamese coffee after all. What’s the best grind size for that purpose?

For brewing Vietnamese coffee in a Phin, it’s best to use a medium grind. This way you have the right balance between brew time and extraction while not ending up with any grounds in your cup. Pre-ground coffee for drip coffee will work reasonably well.

If you want your Vietnamese coffee to be very strong, you can go to a medium-fine grind. This might leave a little bit of residue in your cup though. It’s probably going to be a very tiny amount of residue, especially if your grinder produces an even grind. So that’s a trade-off you can make to get a very strong cup.

Besides grind size, the water temperature is important as well. Find the best water temperature for Vietnamese coffee here.

This recommendation is for using a Phin (Traditional Vietnamese filter). If you’re going to make Vietnamese-style coffee with another brewing method, use the recommended grind size for that specific method.

If you want more detail about why the grind size matters for a Phin? I’ll go into more details below. Also, at the bottom, you can see how to troubleshoot your Phin if it doesn’t seem to be working right.

If you need more information about what a Phin is and how to use it correctly, check out this article.

Getting a decent hand grinder will improve the taste of your coffee dramatically over pre-ground coffee. Most hand grinders have no problem grinding medium or medium-fine coffee. A Phin is quite small so check out the Hario Slim grinder. It’s easily adjustable in size and holds more than enough grounds.

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Why does grind size matter?

Why does grind size matter? It doesn’t only matter for brewing coffee with a Phin but for every brewing method.

Brewing good coffee is a balancing act. You have to balance quite a few factors to get a good-tasting cup. Below I’ll go into some of those factors and how they relate to the grind size you use for your Phin.

Coffee grind size matters for Vietnamese (and other styles of coffee) because of these things;

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Grounds in cup

In a Phin, and actually any other brewing method, the minimum grind size is decided by the size of the holes in the filter medium.

You don’t want any grounds ending up in your cup. It’s pretty simple to prevent this. Just make the size of the coffee granules bigger than the holes in the filter. That way the water goes through but not the grounds.

In a Phin, the holes are much larger than in a paper filter. So that’s why you can use a finer grind in a paper filter than in a Phin.

There are a few exceptions like Turkish coffee which has grounds in the cup while you drink it. With Turkish coffee, you don’t really use any kind of filter so you just have to be careful while drinking. However, most other places in the world don’t like grounds in their coffee so you want to keep those out.

On the other hand, you don’t want to go too big either. Because the water won’t extract all the coffee and the brew time will be too short.

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Brew time

Another important factor you have to balance is the brew time. Brew time is a proxy for extraction. Different brewing methods take a different amount of time to run the water through the filter and get the best result.

A paper filter uses a finer ground than a Phin and lets water through much quicker than a Phin. Because the coffee grounds are fine, the water can extract everything from them much faster. A finer grind means you have more surface area per gram of coffee. More surface area means the water can touch a bigger area and extract more from the grounds in less time.

What’s the difference between Vietnamese and Paper filter coffee?

Because the size of the coffee granules in a Phin has to be a bit bigger, you have to give the water more time to extract everything. So as a result the brew time has to be longer. For a Phin, you want to shoot for a brew time of around 6 minutes. To get to that time, you have to get the right grind size.

If the grind size gets too big, it means there will be bigger holes between the granules which lets water through quicker. If they’re too small, it’ll block up the filter and get into the cup. So that’s why getting it right is important.

This goes for a Phin but also other types of coffee filters. With other filters, you just need a different granule size to balance the brew time and extraction.

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Why does my water run through Phin too fast?

Maybe you’ve got the grind size right as per recommendations but the water still goes through the filter way too fast. What’s going on?

There are a few reasons why the water runs through the Phin too fast;

You can try to adjust the grind slightly finer for the next cup but there is a limit to how fine you can go because it can plug up the holes in the filter or get into the cup. That’s not what you want to happen. If it’s still running too quickly with a fine grind, one of the following things might be going on.

Why is Vietnamese coffee so thick? Find out in this article.

The biggest reason why this is happening is because the coffee isn’t compacted in the filter enough. You’re supposed to compact the coffee grounds in the filter. You can do this the following way;

Don’t forget to let the coffee ‘bloom’ after compacting but before pouring in all the water. Pour 15-20 ml of hot water into the filter. This is just enough to be absorbed by the grounds without letting any coffee through. What this does is let the coffee grounds swell up a little bit, filling up more air gaps. It also helps to release all the compounds, aromatics, and oils from the grounds.

Another reason might be that you’re simply not using enough coffee grounds in the filter. There has to be a bed of grounds of about 1cm thick after compacting. For filters that brew a single cup, 25 grams of coffee is a good place to start.  

Why is Vietnamese coffee so strong? Find out here.

Obviously, a coffee bed that’s too thin will let the water pass through quicker. Weighing out 25 grams of coffee will help you get the right amount. If you don’t have a scale, 3 heaping spoons of coffee grounds should be pretty close.

Before adjusting your grind size, try the tips above. One of these things might be the problem, not the size. If none of this works, then it’s time to try a finer or coarser grind.

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My Phin doesn’t drip at all

The opposite of coffee getting through too quickly can also happen. Sometimes just nothing happens at all, what’s going on?

There are a few common reasons;

I’ve also found that older ground coffee that was left in the open air for too long and therefore got a bit damp, tends to clog up the filter as well. I’m not quite sure why that is but if your coffee grounds haven’t been saved in an air-tight container, that might be the problem.

Find the 5 most famous Vietnamese coffee brands here.