What puck distribution means for espresso extraction
David Phillips talks to Mateus Maneschy about the importance of good puck distribution and how to achieve it.
Puck distribution plays a crucial role in achieving balanced and even espresso extraction.
A good grinder with sharp burrs will certainly help deliver a consistent grind seize, which helps to deliver even extraction. However, this can be made redundant by poor puck preparation.
With good puck prep, each coffee particle has the best chance of being extracted the same as the one next to it. This will give more balanced flavour profiles and more clarity in the cup.
Despite this, the coffee puck does not extract evenly. Typically, water passes through the puck at different flow rates and temperatures during extraction, and therefore extracts the particles at different rates.
For baristas adjusting pressure, flow rate, and temperature to address these differences (or accentuate them), an evenly distributed puck acts as a control – so they can make informed decisions when setting their profiles.
The principal reason for ensuring good puck distribution, however, is to prevent extraction issues such as channelling.
“In any type of espresso extraction, you want to avoid what we call channelling,” says Mateus Maneschy, barista at Tomorrow at 9. “This is when you don’t have an even puck, so the water finds an easy channel to pass through. To get an even extraction, you want the water to pass through all the coffee and extract everything evenly.”
When channelling occurs, coffee ends up being both over-extracted and under-extracted at the same time – leading to an increase in astringency, sourness, and an altogether inconsistent flavour in the cup.
“If your puck is not evenly distributed when you tamp it, you’re going to have more coffee on one side and less on the other, and more water will pass through on one side,” Mateus adds.
This causes inconsistency in the shots you serve to customers.
“You don’t want to send two single espressos to a table when they taste different,” says Mateus. “And even if you put them into the same cup to make a double espresso, it’s simply like mixing an over-extracted and under-extracted coffee together.”
Puck distribution methods and tools
Over the years, several methods have emerged to achieve even puck distribution.
These have developed over time. As higher quality standards began to be introduced with the rise of specialty coffee, baristas often used the NSEW method. This involved smoothing a finger over the top of the portafilter from north to south, then east to west, to evenly distribute the coffee grounds within it.
Similarly, the Stockfleth method involves forming an L-shape by placing a thumb along the rim of the basket and the index finger straight across, then rotating your hand and the portafilter in different directions until the coffee grounds are evenly distributed.
Since then, however, various tools have entered the market which aid puck distribution.
“If you are aiming to get a perfect extraction at a high level I would definitely recommend getting a WDT – a Weiss Distribution Tool,” says Mateus.
The WDT uses fine needles to stir the coffee within the portafilter, thereby preventing clumping. Clumping is caused by an accumulation of static electricity at finer grind sizes in the grinder. If they aren’t broken up, this can cause water to find the path of least resistance – thereby forming channels and leading to uneven extraction.
“When you have an even distribution but you don’t use a WDT you’re still likely to have some clumps in the puck,” says Mateus. “The WDT is made to solve this.
“It’s not that good for café workflow – more for homebrewing, or the moments when you have time to actually brew the best cup possible.”
Many puck distribution tools can be impractical for use in a café, particularly one with high footfall. While home brewers have the time to prepare their puck as best they can, baristas need a method that balances efficiency and effectiveness. This has made levellers a popular option for coffee shops.
“They are not enough for the best extraction possible, but they are a good thing to use,” says Mateus. One downside to using a leveller is that they do nothing to address clumping – and can even accentuate the problem. Nevertheless, it does effectively level the puck and is a quick tool to use.
“It’s really easy and they don’t affect workflow that much in a café,” says Mateus. “Even on the busiest days, it doesn’t take me more than 10 seconds to prepare the puck if the grinder is fast enough.”
Mid and post-extraction analysis
The task of evenly distributing the coffee puck occurs before extraction starts. However, there are methods to assess the effectiveness of puck distribution during and after the shot has been pulled.
Once the shot has finished, analysing the spent puck can reveal signs of channelling, such as cracks or air bubble holes.
Additionally, using a bottomless portafilter enables baristas to check for channelling, side-channelling, spurting, or blonding during the extraction process. These issues may indicate problems with puck preparation.
“Some people think that in the beginning, you’re going to have this beautiful centre pour – but no,” says Mateus. “At first the coffee will start coming from everywhere until all the drops connect.
“If they don’t connect, the extraction is not even. If they connect in up to 10 seconds you’re going to have a good extraction and can probably expect a good cup of coffee out of it.”
Ultimately, puck distribution is crucial for a balanced, high-quality cup of coffee. Homebrewers have the time to perfect this process, but coffee shops need to adopt a solution that is both foolproof and efficient.
One thing that is widely accepted – good puck distribution is vital for pulling high-quality shots of espresso.