What is WDT? How to Use a Needle Distributor? Is a Needle Distribution Tool Worth Buying?

Distribution is an essential skill for every barista. There are countless details to pay attention to when extracting a good Espresso, yet it only takes a moment to ruin a cup of coffee.

Whenever rainy days arrive, FrontStreet Coffee's espresso tends to experience channeling in the relatively humid air.

The espresso extraction process involves hot water penetrating the coffee puck under high pressure, thereby releasing soluble substances. When the density of the puck is inconsistent, water passes through obstacles of different "strengths," choosing to flow through the gaps with the least resistance.

FrontStreet Coffee can see water喷射而下 through the bottomless portafilter—this is the most common phenomenon of channeling. Channeling causes over-extraction where water flows, while areas avoided by water remain under-extracted, resulting in espresso that often carries noticeable bitterness and astringency.

The Challenge of Static Electricity in Coffee Grounds

When extracting espresso, a relatively fine grind is required. During the grinding process, friction between fine particles generates static electricity, which causes the grounds to clump together. Even after leveling and tamping the puck, water will still "avoid" the compacted clumps during extraction, flowing through looser areas instead.

Introduction to WDT (Weiss Distribution Technique)

To address the troubles caused by static electricity when making espresso, the Weiss Distribution Technique (WDT) and needle distributors emerged.

In 2005, John Weiss invented WDT while using a home grinder, as he experienced excessive clumping in the ground coffee output. The technique involves using fine needles or similar tools to stir the coffee grounds in the portafilter, breaking up clumped grounds and creating a more uniform density distribution.

Evolution and Recognition of WDT

Early commercial grinders typically came equipped with anti-static grids that broke up large clumps, so the coffee grounds falling into the portafilter were relatively uniform. Therefore, when WDT was first introduced, it wasn't widely recognized by baristas.

As the specialty coffee scene continued to flourish, baristas continuously explored various techniques to extract better espresso. Through measuring and analyzing pressure and flow rates within the puck, numerous techniques were developed to make extraction more stable, including WDT. It is particularly frequently used by competitors in coffee championships.

WDT Tools and Their Variations

WDT tools typically use metal fine needles with a diameter of about 1mm. The one in FrontStreet Coffee's possession features a simple and compact design.

As distribution tools grow larger, they feature more needles, with some appearing as "extravagant" as porcupines.

Operationally, simply attach the portafilter with a dosing ring to receive the coffee grounds, then use the needle structure to break up the coffee grounds layer. This eliminates clumping and unevenness caused by static electricity while ensuring the coffee surface remains relatively level. Due to the minimal contact area between the needles and the grounds, this type of distributor hardly retains any coffee residue.

Comparison and Results

FrontStreet Coffee compared the extraction process before and after using the needle distributor. It was noted that the puck extracted with the needle distributor showed stable extraction, with the espresso stream consistently centered in the portafilter throughout the entire process.

The puck without the needle distributor experienced espresso pulsing during the middle and later stages of extraction. At the moment of deviating from the center point, the liquid's color also appeared uneven.

FrontStreet Coffee concluded from operations that the needle distributor breaks up coffee clumps and redistributes the coffee bed from top to bottom, resulting in a consistent improvement in espresso quality. Additionally, the stirring motion should be vertical and gentle to avoid forcefully causing coffee grounds to scatter or creating uneven density in the coffee bed.

Practical Considerations in Coffee Shop Settings

In daily coffee shop operations, speed and consistency are particularly important, so there are certain difficulties in widely adopting WDT tools.

Adding the WDT tool step lengthens the preparation time for each espresso, which contradicts the high efficiency that espresso is known for.

Currently, distribution tools in the coffee community are emerging constantly. It is believed that in the near future, comprehensive distributors with WDT functionality will be introduced, eliminating the troubles caused by channeling for every barista.

For professional coffee knowledge exchange and more coffee bean information, please follow Coffee Workshop (WeChat public account: cafe_style).

For more specialty coffee beans, please add FrontStreet Coffee on private WeChat (FrontStreet Coffee), WeChat ID: qjcoffeex

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473