Why Is My Aeropress Coffee Weak? 5 Causes And Fixes


Is your Aeropress not brewing coffee as strong as you’d like? An Aeropress should brew coffee that’s a bit stronger than pour over filter coffee in just a few minutes. If yours doesn’t do this, here are some things that could be going wrong. 

The most common reasons for weak coffee from an Aeropress are; not enough grounds, a short steep time, a coarse grind size, not stirring enough and not letting the coffee grounds bloom. An Aeropress should brew stronger coffee than a pour over method but less strong than espresso.

Below you can find out more about these five reasons and how to fix them so your Aeropress makes the best coffee possible. 

Not Enough Grounds

first thing to check when your coffee isn’t strong enough is to check how much coffee grounds you’re using. It’s something pretty basic but that means getting it right is very important. 

Other factors below can impact how strong your coffee comes out and the balance of taste but you need to put in the right amount of grounds to get good results to begin with. 

For a full Aeropress (water up to number 4), 15 grams of grounds should be used. Weighing with a coffee scale is advisable. That way it’s easy to be accurate every time. Weighing also makes it a lot easier to change the recipe if needed for next time. 

However, if you don’t want to weigh your coffee every time, a coffee scoop will get you pretty close. The average coffee scoop contains 7 grams when leveled. Of course not every scoop is the same so weighing one time can help you figure you how much grounds is in one of your scoops. 

Short Steep Time

One of the most common reasons Aeropress coffee comes out a little weak is that people don’t wait long enough for the coffee to properly steep. An Aeropress is an interesting combination of a percolation and infusion brew method. The coffee gets pushed through the grounds under a little bit of pressure. That pressure helps extract the grounds but just waiting a little longer before you push down is a good thing, especially if you want to make your cup a bit stronger. 

Steeping is the process of simply waiting and letting the water and grounds just hang out together for a while. In an Aeropress you do this by simply filling up the chamber with water and putting the plunger on top but don’t press down. The seal created by the plunger prevents the coffee from dripping out. 

How To Fix This

Coffee is similar to tea. The longer it’s steeped, the stronger it gets but you also have a chance of more bitterness. 3 minutes works well for lighter roasts in my experience. 2 minutes is good for medium and darker roasted coffee. Timing how long you are actually waiting is a good idea since it’s pretty hard to gauge how long you’ve been waiting, especially for your morning coffee. Timing also helps with changing the steep time since you know exactly how long you’ve steeped last time and how to change it.  

Many people gauge the strength of their coffee by how bitter it is. Bitterness says something about how far extracted the grounds are but not necessarily about how much ‘taste’ or caffeine there is in the cup. 

Grind Size Too Coarse

Another reason why your Aeropress doesn’t brew very strong coffee is because the coffee is ground to coarsely. The finer coffee grounds are, the quicker they are extracted and thus brew stronger coffee in the same time. An Aeropress works best with grounds that are relatively fine. 

If the grounds are too coarse the water simply doesn’t penetrate all the way to the middle of the particles before you push down the plunger. That means a lot of the coffee grounds aren’t ‘used’ properly and you get a lot less taste compound get into your cup. 

Also, because the coarse coffee particles have bigger gaps between them, they create less resistance when pushing down the plunger. Instead of pushing it through the grounds, you push the water through the gaps between the grounds. 

Less resistance also means less pressure which leads to lower extractions. That combination of bigger gaps and less resistance (and thus pressure) creates weaker coffee. 

How to Fix This

If you grind your own coffee, simply adjusting the grinder to a finer size is the best solution. You’re looking for a consistency slightly coarser than espresso, similar to what it would be for a moka pot. This is also known as ‘medium-fine’. Most of the particles should be around 0.5 mm in diameter. 

If you buy your coffee pre ground, it’s a bit more difficult. You would get much better result by grinding your own fresh beans but if that’s not something you’re interested in, the best option is to increase the steep time. 

An extended steep time gives the water more time to penetrate deeply into the coffee grounds and extract all the taste.

Another option if you want to stick with pre-ground coffee is, getting it ground at your local coffeeshop/coffee roaster. They will often grind to order so you can tell them exactly what you want and what you want to use it for.

Stirring Technique

It’s best to stir the grounds when brewing with an Aeropress. This makes sure all the grounds are properly wet during the bloom phase and speeds up extraction, making the coffee stronger. 

There are just as many recipes as ways to stir an Aeropress. In my experience, one stirring session when after pouring in enough water to bloom the grounds is necessary to really get all the grounds wet. 

The second stirring session is usually after the steep. This helps extract the last bits of taste out of the grounds. Think about dissolving sugar or salt in water. Does it dissolve faster when it’s stirred or when you just let it sit? Coffee is the same. 

If you think your coffee isn’t strong enough, stirring two times is a good idea. However, it can have as a side effect that the coffee also becomes very bitter. If it’s too bitter depends on the coffee and your taste. 

No Bloom

Letting coffee ‘bloom’ is important with pretty much every brew method and the Aeropress is no exception. The bloom time helps get all the grounds wet, releases Co2 from the grounds before brewing and helps to make it easier for the rest of the water to get in and do their job afterwards. 

Blooming coffee is the process of simply pouring on a little bit of water (usually 2x the amount of grounds in grams) and then waiting for about 30-45 seconds. 

If you don’t do any bloom at the moment, try it and see what difference it makes. Simply pour in a little bit of water, stir to get all the grounds evenly wet and wait for 30 seconds before pouring the rest of the water in. 

If you already do a bloom, you can try extending it to 45 seconds but this likely won’t be your main cause for the coffee being too weak. 

Does An Aeropress Make Weak Coffee?

An Aeropress shouldn’t make weak coffee. It won’t make coffee as strong as espresso but it tends to make coffee that’s stronger than a pour over method would. The smoother taste might make it seem like an Aeropress makes weaker coffee while actually the taste is just different.

Most people judge the strength of coffee by the amount of bitterness. However, that’s not necessarily fair. Caffeine has a bitter taste but that really harsh bitterness doesn’t mean your coffee has more caffeine. It just means the grounds were really far extracted. The last compounds that dissolve in the water are the most bitter. 

An Aeropress makes it easy to make coffee that lacks that intense bitterness by just following a few easy steps, making some people believe it’s not strong while it has the same amount of caffeine. 

Try a Fellow Prismo

Tried all of the things above and still don’t have the coffee strength you like? There is something you can add to your Aeropress that helps you brew something that’s much more like espresso. 

The Fellow Prismo is a little device that replaces the filter cap of the Aeropress. It’s a metal filter screen (which means no more paper filters), and a plastic cap with a little valve. 

This little valve only opens when a certain pressure is reached. That means this allows you to push much harder on the plunger before the liquid starts coming out. That results in a higher pressure in the brew chamber which created a condition more like espresso. The higher pressure, combined with the lack of paper filter will brew much thicker, stronger coffee. 

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