Espresso Channeling (Main Causes and How To Fix It)

Espresso channeling is a problem bound to be faced by every barista and home brewer somewhere along their coffee journey.

Simply put, the problem of espresso channeling is when high-pressure water found an easy pathway past the bed of the coffee puck during coffee brewing. When this happens, you will end up with a watery espresso. 

It tastes absolutely disgusting and you definitely cannot use that as a base for any espresso-based beverages. 

If this sounds like a problem you have, fret not!

In this post, you can find the probable causes of this issue and what you can do to stop espresso channeling. By the end of it, you will definitely be able to pull high-quality espresso shots. 

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At a glance: Espresso Channeling (Main Causes and How To Fix It)

What Is Channeling In Espresso?

Channeling in espresso is when water flows through the coffee grounds unevenly. In most cases, the high-pressure water will find the path with the least resistance within the coffee puck to flow through. 

As a result, most of the water will pass through these paths, usually holes and cracks within the coffee puck. In these areas, the coffee grounds will be oversaturated with water and this causes over-extraction in these regions.

Under-extraction on the other hand will occur in the other areas which have lesser exposure to water.

The combination of over-extraction and under-extraction of the coffee grounds will yield a cup of coffee that is imbalanced. Hence, channeling can either cause espresso to taste overwhelmingly bitter or just plain sour without the crisp acidity.

How Does Espresso Channeling Affect Espresso?

1. Bad Tasting Espresso

Since uneven extraction is a result of channeling during espresso brewing, the first and most evident effect is the taste and flavor of the espresso. 

In essence, unevenly extracted espresso yields a very watery espresso that is weak and flat tasting. On top of that, you will not be able to taste the naturally occurring acids that are present in the coffee beans.

Instead, what you can taste is just unpleasant sourness and bitter aftertaste.

The imbalance in flavors makes the espresso not very palatable and simply tastes like bad coffee.

2. Lack of Crema

Other than that, the channeling effect also affects the physical look of the espresso shot. 

A proper espresso is made of three distinct layers; crema, heart, and body. However, if you have a case of channeling during your espresso brew, you will get none of these distinct layers in your espresso.

In fact, the most obvious hint of espresso channeling is when you notice little or almost no formation of crema on top of the espresso. 

With the presence of cracks within the coffee puck, it cannot provide enough resistance to build up pressure in the portafilter. And since there is insufficient pressure, the espresso brewing process is not able to emulsify the coffee oils with Carbon Dioxide gas to form the crema layer.

3. Exceed Normal Espresso Volume

In terms of volume, the espresso shot will exceed the typical 2 oz (60 ml) volume for a proper espresso. This is because of the formation of channels within the espresso puck where more water will flow through easily. 

So in summary, espresso channeling produces weak watery espresso which does not have a character in terms of taste and flavor. 

Causes Of Espresso Channeling

Now that we have understood channeling in espresso, it is time to look at the root causes of this problem.

All in all, there are 5 main causes of espresso channeling that you should know about.

1. Grind Size Too Coarse

Coffee grind size is probably the very first factor that you should look into when you have a problem of channeling when you pull an espresso shot.

In general, whole-bean coffee which is ground too coarsely will definitely lead to espresso channeling. This is because coarse coffee grounds do not encourage compact arrangement and this leaves too much space in between the coffee grounds.

Under a high-pressure environment, these spaces become easy pathways for water to flow through during espresso brewing. 

2. Weak Tamping Pressure

While tamping is essential to pack the loose coffee grounds into a bed of dense coffee cake, tamping too lightly will lead to the channeling effect.

Without enough tamping pressure, the coffee grounds will remain structurally loose. High-pressure water from the espresso machine will break through the bed of coffee with minimal effort and cause multiple fractures within the coffee’s puck. 

In general, the recommended tamping pressure that is widely accepted as the norm within the coffee community is 20-30 pounds (9-13 kg of pressure).

Author’s Note: Tamping too hard will also lead to an adverse effect. This will cause the coffee grounds to be too tightly packed and causes too much resistance to the flow of water.

3. Poor Dosing

Poor dosing of coffee grounds is another factor that is often overlooked that could cause channeling during espresso brewing. 

Every portafilter basket is only meant to take a specific weight range of coffee grounds. For instance, a single shot portafilter basket the recommended weight of coffee grounds is 11 grams while double shot portafilter basket optimally requires 18 grams.

If you were to dose your coffee grounds below these levels, there will not be enough coffee grounds to build the required resistance during espresso brewing. The high-pressure water from the espresso machine can easily break the coffee puck and open a pathway for water channeling.

That said, a deviation of 1 to 2 grams is still within the acceptable limit. 

4. Uneven Coffee Distribution

After dosing your coffee grounds into the portafilter, you will most often find the mound of coffee grounds to look like a cone. This is why baristas will have to distribute the coffee grounds with either their hands or a distribution tool.

If done incorrectly, you may sweep more coffee grounds to a corner while leaving the other parts to have lesser coffee grounds. Tamping an unevenly distributed coffee will cause one side of the coffee puck to be denser and the other.

Obviously, the less denser area will be the weaker zone and hence more prone to cause channeling during espresso extraction.

5. Incorrect Tamper Size

Last but not least, using an incorrect tamper size will also lead to an espresso channeling effect. 

If your portafilter size has a 58 mm diameter, please do, by all means, use a 58 mm tamper. 

Using an incorrect tamper size will cause uneven leveling of the coffee grounds in the portafilter. Pressure distribution throughout the bed of coffee will be unevenly distributed and this causes a small part of the coffee grounds to be loose.

As a result, when high-pressure water hits the bed of coffee grounds, the loosely packed region will immediately crumble and open a pathway for water to flow through easily. 

How To Fix Espresso Channeling Problem?

Since we have identified the causes leading to channeling during espresso brewing, preventing it is fairly easy. 

Here are some adjustments you can take to fix an espresso channeling problem.

Use Finer Grind Size

Coffee grounds that are finer in size leave lesser space between each coffee ground particle. As a result, the coffee bed in the portafilter will pack uniformly to form a dense cake of coffee. 

So if you notice channeling during your espresso brew, try making small reductions in the coffee grind size until you get a mousetail-like espresso flow.

An easy way to solve this is to use a decent electric coffee grinder with a flat burr (not a grinder that is meant for spices!). These types of coffee grinders give the most consistent grind sizes.

Adjust The Tamping Pressure

Tamping coffee grounds can be fairly tricky and the way around it is through constant practice. 

A simple hack around this is to hold your tamper and press it on a weighing scale. While doing so, adjust your strength such that it exerts 20-30 pounds of force on the weighing scale. 

Once you have grasped the necessary strength needed, practice tamping your coffee grounds with the same exact pressure until it becomes muscle memory.

If this is still difficult for you to grasp, the barista community has recently developed a calibrated tamper. This little device almost guarantees consistent tamping pressure each time!

Adjust Tamping Angle

In addition to the tamping pressure, you will also have to be wary about the tamping angle. The right way is to angle your elbow to form a 90^o angle perpendicular to the portafilter. 

This ensures level tamping of the coffee grounds which in turn creates a flat surface for the water to flow through evenly.

Unfortunately, there are no tools to help you with this. All you need here is constant practice!

Ensure Proper Dosing 

Every portafilter is meant to take a designated amount of coffee grounds.

As a rule of thumb, single-shot filter baskets use 9 grams of coffee grounds while double-shot filter baskets require 18 grams of coffee grounds.  

If a finer grind size and proper tamping do not solve your espresso channeling issue, try using a slightly larger dose of coffee. 

A quick and simple way around this is to weigh your portafilter before and after you dose the coffee grounds. To help you with that, I’d highly recommend getting a calibrated and precise digital scale to ensure proper dosing amounts each time. 

Use A Fitting Tamper Size

Always use a tamper size that exactly fits the inner diameter of the portafilter. This is extremely important when you tamp the coffee grounds. 

A tamper that fully fits the portafilter’s inner diameter will be able to level the coffee grounds evenly. This in effect allows even distribution of pressure on the bed of coffee grounds and henceforth even extraction of your espresso.

How To Spot Channeling In Espresso?

If you are just starting out brewing espressos, chances are you may not know how to spot channeling in espressos. 

Here are some of the most compelling telltale signs that will indicate that espresso channeling is happening:

Rapid Flow Of Espresso During Extraction

As your espresso flows out of the portafilter spout, it should look golden brown with a mousetail-like flow. On top of that, the gentle flow should last throughout the whole process of espresso extraction which is approximately 30 seconds.

If the flow of espresso becomes turbulent and appears to be gushing out of the portafilter’s spout, it is no denying that espresso channeling happened.

Watery Looking Espresso

Whether you are extracting an espresso or a ristretto, the shot should look thick with a clear definition of the espresso layers; especially the crema. 

If notice that your espresso looks watery and the crema looks thin or non-existent, these are clear indications of channeling during espresso extraction. In this case, the physical look of the espresso tells you that there is excess water flowing through the coffee puck.

Wet Coffee Puck

By looking at your coffee puck in the portafilter, you can easily tell if you have a channeling problem. In fact, you can pinpoint the location where the channeling happened. 

The coffee puck will look wet and muddy with some of the following traits:

• Uneven surface with sunken areas.
• Surface area with formation of cracks.
• Evident holes on the coffee puck’s surface.

Weak Tasting Espresso

It is common knowledge that espresso tastes strong and intense. While it packs a punch, the espresso is a flavor bomb with a combination of naturally occurring acids present in the coffee beans themselves. 

Therefore, if your espresso tastes weak and boring, it is highly likely that there is too much water flowing through the bed of coffee due to espresso channeling.

Author’s Note: Sometimes, off-tasting espressos can be due to the coffee being old and past its shelf life. So it is essential to use the freshest beans possible for espresso brewing. 

FAQ On Espresso Channeling

What Does Channeled Espresso Taste Like?

Channeled espresso tastes sour with a bitter aftertaste. This flavor profile is a result of a combination of over and under-extraction of the coffee grounds. The over-extracted part that contributes to the bitter-tasting profile is the denser region of the coffee puck. The sour-tasting profile comes from the region where channeling happens.

Can Grinding Too Fine Cause Channeling?

Grinding too fine will not cause channeling. Coffee grounds that are too fine will however cause the coffee puck to be too tightly packed. As a result, water will face high resistance and will not be able to penetrate the bed of coffee grounds. This is known as over-extraction and the espresso-tasting profile will lean towards the bitter end.

Why Is My Espresso Puck Wet After Extraction?

The main reason why your espresso puck is wet after extraction is that there are not enough coffee grounds in the portafilter. Without enough coffee grounds, there will be a huge gap between the bed of the coffee grounds and the shower screen. Therefore, there will not be enough coffee grounds to absorb the residual water from the shower screen at the end of the extraction process.

Closing Notes

That concludes all you need to know about espresso channeling. By implementing the steps above, I am almost sure that the channeling problem will be a thing of the past.

This is extremely important as the taste of espressos is highly reliant on the quality of the extraction process. When done right, espressos are a highly complex beverage with a depth of flavors.

And so, solving the channeling issue is the first step in the right direction towards better espressos!

If you find this piece of article informational and have taught you a thing or two about espresso channeling, please share it with your fellow friends, baristas and home brewers! 

Happy brewing!