What does the first coffee machine tell us about WDT?

Humid weather makes coffee grounds clump, and clumps cause channeling during espresso extraction. The Weiss Distribution Technique, or WDT, uses fine needles to stir the bed and break those clumps apart. Many home baristas ask whether a toothpick can do the same job, and Front Street's extraction tests compared the two on breakup, bed evenness, and stability.

The results show toothpicks are too thick and too few to open clumps evenly, so the bed stays uneven and shots vary. Needle tools spread grounds more consistently, which matters more than any single piece of gear history, including the first coffee machine designs. Buying advice: pick a tool with many thin needles and use it before tamping.

In humid weather, coffee grounds tend to clump, which in turn causes channeling during espresso extraction and affects flavor performance. The WDT (Weiss Distribution Technique) breaks up clumps by stirring with fine needles, making it an effective solution to this problem. But not every enthusiast keeps distribution needles on hand, so whether everyday items like toothpicks can serve as substitutes has become a common question. This article, based on Front Street's actual extraction experiments, compares distribution needles and toothpicks in terms of breaking-up effectiveness, grounds bed distribution, and extraction stability, analyzes why toothpicks are unsuitable as substitutes, and offers buying advice for distribution needles, helping you achieve more stable espresso in rainy or dry seasons.

Guangzhou has seen frequent thunderstorms lately, and the weather of heavy rain accompanied by thunder and lightning is expected to last about another week. During such humid times, making espresso always becomes noticeably more difficult. The reason is that when humidity is high, coffee grounds are more prone to sticking together and forming clumps during grinding, and once clumps enter the brewing stage, they easily give rise to channeling, which ultimately shows up in the taste of the coffee.

If you want to reduce the likelihood of channeling and make the espresso extraction process and flavor performance more stable, you must tackle the root cause—breaking up the clumped coffee grounds. The method is actually not complicated; with the help of a "needle-type distribution tool," it can be effectively solved.

The needle-type distribution tool, commonly known as a distribution needle. As shown in the picture above, the front end of this kind of tool is densely packed with many fine needles. Inserting it into the coffee grounds and stirring breaks up the clumps, and the possibility of channeling decreases accordingly. Because this technique was pioneered by John Weiss, it is called the Weiss Distribution Technique, or WDT for short.

However, not everyone has a distribution tool at home. After all, rainy days do not occur often, and the impact of channeling is relatively limited, so the necessity of specifically buying distribution needles is not high. As a result, many friends, when encountering clumped coffee grounds, start to wonder: since breaking up coffee grounds relies on those fine needles at the front of the distribution tool, would using similar items as substitutes achieve the same effect?

Next, let Front Street test it through actual operation to see whether the needle-type distribution tool can be replaced by other needle-like items.

Extraction Experiment

After looking up information online, Front Street selected the substitute for this experiment—"toothpicks." The reason is that toothpicks are currently the thing most often used as a substitute for distribution needles, related posts can be found with a single search online, and they are extremely convenient to obtain—you can get them by ordering takeout.

In this experiment, Front Street will extract three espressos for verification, using toothpicks to break up the coffee grounds before each extraction. The parameters are set as 20g of grounds and a grounds-to-liquid ratio of 1:2 (that is, extracting 40ml of coffee liquid), then observe whether channeling occurs during extraction. On the premise of no channeling, the average time for 20g of grounds to extract 40ml of coffee liquid is about 30±2 seconds; this is the result Front Street obtained after extracting three espressos with distribution needles.

First, let me briefly explain the extraction process and taste performance of these three coffees, so that they can later be compared with the toothpick substitute version: the three coffees were in a consistent state, with no spraying during extraction, balanced flavor, clear layers, and a smooth and mellow mouthfeel. That concludes the introduction.

Next, switch to toothpicks instead of distribution needles and, under the same parameters, see whether toothpicks can achieve an effect similar to distribution needles. The specific steps are as follows:

① First, dose the coffee grounds into the portafilter basket.

② Take out two toothpicks, offset their positions, and stir the coffee grounds in the basket.

③ After stirring, tamp the grounds bed and attach the group head to begin extraction.

④ When the coffee machine has extracted the target liquid weight, close the water valve and stop extraction.

Afterward, Front Street extracted two more espressos following the same procedure. By observing the flow state during extraction and tasting the flavor, the conclusion was reached: toothpicks are not suitable as a substitute for distribution needles.

There are two reasons. First, toothpicks are too thick. Each needle of a distribution needle is extremely fine, so it can break up coffee grounds without disturbing the original distribution of the grounds bed. The diameter of a toothpick far exceeds that of fine needles, and when stirring it pushes the coffee grounds to the sides, not only greatly reducing the breaking-up effect but also changing the grounds bed distribution (the coffee grounds are easily pushed out of the basket).

Second, toothpicks are hard to hold. Unless some kind of tool is used to fix the toothpicks in place, it is impossible to use multiple toothpicks at the same time to break up the coffee grounds. This significantly weakens the effect of breaking up clumps, so these three espressos stirred with toothpicks still showed spraying during extraction. Naturally, there were slight flaws in taste as well, though not serious.

(One was accidentally poured out.)

Overall, toothpicks and items of similar thickness are not suitable as substitutes for distribution needles. Only needle-like objects thinner and more "slender" than them are suitable for breaking up coffee grounds, though using such items also comes with the trouble of being hard to hold.

So, if you pursue coffee flavor highly and strive for perfection, it is best to keep a distribution needle. After all, it is not only humid weather that causes coffee grounds to clump; dry seasons prone to static electricity do the same. The price of distribution needles varies by size; cheap ones, like the one in Front Street's hand, cost only a single digit, while expensive ones can reach four digits. How to choose is up to you; anyway, Front Street basically has no use for them.

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The above content is compiled by CoffeeHunters, a coffee news website.