What is WDT? How to Effectively Distribute Coffee for Even Extraction

 

In the past month we have learnt how to preheat our BRUA correctly and the importance of setting our grinder for the best shot possible. This is because the best equipment in the world won't make coffee by itself! It requires a user who understands the process for it to be used properly.

Luckily, we're here to help!

We will be covering the crucial steps to achieve even coffee extraction by looking at "distribution" and "tamping".

In the industry we call this puck prep or preparing the coffee bed.

Taking some time here and getting this right will be the difference between achieving consistent coffee results, or coffee that doesn't seem to come out right and is forever changing.

Our goal is to not only tell you how to do this, but to also explain why this is important because the more you understand the process and technique, the more you can troubleshoot and adjust the variables yourself.

Distribution

When we extract coffee, we are not simply creating one extraction. It is in fact millions of small extractions that combine together to create our espresso.

 

 

It is best to think of the yield (extracted coffee) in the cup as an average of all the micro-extractions that occur at the same time. If water moving through the coffee bed is not creating one extraction, but in fact lots of little extractions, it is important that the water flows through them all as even as possible. This is so that we don’t get over extracted particles (too much water flowing through them) and under extracted particles (not enough water flowing through them).

This extraction problem is controlled by distribution.

If we position the grinds throughout the coffee bed evenly, then place an even shower of water to saturate the coffee bed, in theory we should create an even extraction throughout.

The issue with pushing water through an uneven coffee bed is that water will always find the path of least resistance. If one side is not as dense as the other, water will flow through the less dense area quickly (channelling) while the other side will remain relatively untouched by the water. 

In summary, coffee particles need to be distributed with an even density throughout the whole coffee bed so that the water flows through the entire puck at the same rate, extracting all the coffee evenly as possible.

When a coffee extraction channels, we can have a final cup, that is both under extracted and over extracted - tasting both sour and watery, yet bitter and hollow.

This is why it's so important to employ good puck-prep technique when dialling coffee in. Below are a few distribution techniques you may like to try.

 

 

How to Distribute?

There are a few different techniques for distribution. Today we will cover some methods that work best with the BRUA.

Because manual espresso requires a finer coffee grind than traditional espresso, it's important to employ the best distribution possible, as the more particles there are and the finer they are, the more chance inconsistencies can arise from poor distribution.

 

WDT - Weiss Distribution Technique

WDT was created by John Weiss in 2005.

His aim was to create a simple way of distributing coffee grinds evenly and to help compensate for the large clumps that occur at finer grind settings. These clumps have different levels of density in your coffee puck than the rest of your coffee bed and can result in uneven extractions.

The technique is simple, however it must be completed correctly for good results.

Using a WDT tool and a dosing funnel, stir the grinds aggressively with a circular motion all the way down to the bottom of the basket.

Once all clumps have been broken up, even out the coffee bed so grounds are distributed evenly with the tool, give the coffee basket one vertical tap on the bench to settle grinds and tamp with firm pressure.

 

Wedge Distributors

Wedge distributors hit the coffee scene hard back around 2018 and while popularity with wedge distributors has declined, many people still love these tools.

They work by sitting level on top of the un-tamped coffee grounds in the basket, rotating slowly and allowing the chisel face of the distributor to move the grinds around the basket in a somewhat even manner, compacting and levelling the grinds into less dense areas while distributing.

Wedge distributors do a good job of eliminating risk and controlling the variables, especially with less experienced baristas and enthusiasts.

Even compared with WDT, less skill or knowledge is needed to operate these correctly. While these are a simple and repeatable way to distribute the coffee grinds, they are not as effective as WDT in the lower half of the basket because they are acting only on the top layer of the coffee grinds. 

Here's how to use a distributor/leveller:

• Place grinds in filter basket using the basket holding ring as a funnel, shake to mostly level grounds.
• Remove funnel and place wedge distributors over basket and spin 4 times or until all grinds have been moved evenly throughout the basket.

The Palm Tap Method (no tools required)

While we always recommend WDT as the best form of distribution, sometimes we don't have all of our coffee with us.

Never fear. If you are without the tools that make our work far easier and more consistent, there are still good old fashion techniques that will get a good result.

Like with anything, practice makes perfect and an experienced barista can actually achieve great distribution with just a palm tap (no tools).

Here's how:

• If you find yourself without tools, dose coffee into the basket using the basket holding ring as a funnel.
• Tap the sides of the baskets horizontally, in the direction where the lowest amounts of grinds are found.
• Tap hard enough to jolt the basket so the grounds move horizontally not just vertically... but not so hard as to propel them from the basket.
• Once you have completed 1-3 horizontal taps, complete one vertical tap to settle grinds and tamp firmly.

 

Tamping the coffee

 

You have done the hard part - distribution.

Now it's time to complete the puck prep and lock all your hard work in position, ready for the extraction.

Tamping coffee often scares people, we see so many different tamps on the market and now automatic tamps!

With all these products available promising to make tamping easier, it goes to reason that it must be complicated, right?

We're here to tell you that with the right technique, it is simple, easy and repeatable.

Follow our steps here and you will be tamping perfectly every time without putting strain on your wrist.

 

Here's how:

• Place the basket on a tamp mat or bench-top and hold the tamper firmly with your fingers on the tamper base to apply pressure evenly in all areas.
• Tamp coffee by aligning your body parallel with the basket, placing direct downward pressure with the arm and elbow bent at 90 degrees.
• Tamp to resistance by pressing directly downward. Once the coffee bed is applying even pressure back (between 10-14kg’s), tamping is complete.

Remember, pushing harder than necessary won't create better results and can actually cause strain and injury over a period of time.

Once you feel the coffee bed resisting back you have completed the process. Please don't try to keep pushing harder, this is where inconsistencies begin. In fact, a slightly softer tamp can often aid the water flowing evenly through the bed of coffee.

Also, don't use a twisting motion or spin the tamper. This might look slick on your Instagram reel, but it will inhibit good puck prep!

That's it. Nothing more to it!

 

 

Summary

From start to finish, the reason behind distribution and tamping is to create an even and consistent coffee bed, to aid in a repeatable, great extraction.

Whichever distribution method you choose from the above, the most important thing is you carry it out the same way every time.

Keeping this method constant will help you make tasty repeatable shots over and over again and in no time it will become muscle memory. It will also assist you with your dialling in process. The more variables you control leading up to the extraction, the easier it is to dial in your coffee.

 

 

Final thoughts

If you have followed our whole series so far on making great coffee with your BRUA, you are on your way to making some of the best coffee in town.

If you continue following these steps, you are most probably applying better technique and starting to control the variables that impact fantastic coffee extraction better than many cafes do!

The best coffee is the one YOU make at home.

So, stay tuned for our next instalment on pre-infusion - how & why to do it properly and why direct lever machines rein supreme for this.

 

Lars and the Newton team.