I've visited the topic of WDT (Weiss Distribution Technique) before in distribution topics, like many people my opinion of using this was really only necessary for grinders creating large clumps. Current testing is showing this may be incorrect. While proper employed deep WDT may reduce workflow it can almost certainly increase extraction, reduce channeling, increase consistency and improve flavour of the espresso.
For the home barista I would recommend this extra step, regardless of which grinder you may be using. For those working on a coffee bar the decision on whether to use this step becomes more complicated. A barista must weigh up the benifits of consistency & improved flavour vs. increased time for puck prep & allowing enough time and attention to preform the technique properly/effectively. My personal opinion on this matter would be to only use it on a cafes black coffee's, such as single origin espresso, where extra time and attention is usually paid anyway. For a house blend latte or similar, I would be of the opinion that the difference, once diluted with milk would be negligible and would not justify the reduced efficiency required to preform the task properly.
What is Weiss Distribution Technique (WDT)?
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 of grinds many (It's safe to say even the best grinders create some small clumping) grinders create. These clumps have different levels of density in your coffee puck than the rest of to your coffee bed, creating an uneven extraction (I recommend reading my earlier post here on distribution and extraction for more understanding on the topic).
How to correctly employ WDT.
The technique is simple, however must be completed correctly or you will not find the benifits you are seeking. Using a WDT tool (either made at home or purachesed from a retailer, this one is great value) and a collar if you have one, place the tool in the coffee bed and rotate small circles moving around the whole coffee bed as indicated below.
This must be completed evenly throughout the whole bed and all the way to the bottom. I recommend moving through the whole bed, then reducing the depth to even the top of the bed, in a total time of 6-8 seconds. The aim is to distribute all the coffee grinds evenly and reduce clumping. For this to become part of your puck prep it is important to carry out the tequnique in a consistent manner time and time again. Like with most stages of your distribution technique, practice consistency and a regimented process, given time it will become second nature.
Testing the Theory.
As I recommend with all topics and techniques that I post. Test and try for yourself, weigh out two doses and try one with and one without WDT. Taste both espressos and note any difference in flavour as well as the extraction time, generally WDT shots may run a second or two slower than non WDT. This slower extraction, with the same grind size, indicates the water is slowly moving through the coffee puck and finding less channels to push through quicker, creating more evenly extracted coffee bed.
If you really love testing this out properly, you can drop 5 shots with and 5 shots without WDT. Ensure the dose and yield is exactly the same for all doses, take notes on extraction time and also taste and give a score out of 10 for taste (yes this can be subjective, but taste should be the most important factor). From here you can find an average score for both methods and see what works best as well as analysing which method was more consistent in deviation of extraction time. If you have access to a refractometer this is an excellent measure to see improvements in extraction.
I love hearing what is working for you guys, so please let me know if this works for you and how your experience was with it.
As always thanks for reading, stay caffinated and lets strive to all make better coffee together 😎.
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