Try the RDT barista technique and improve your coffee preparation. By adding just a few drops of water to your coffee beans, you can achieve better extractions. How does it work?
RDT technique: splash water on the coffee
The pioneer of the RDT method is barista David Ross. After him, this method of coffee pre-treatment is also called, RDT = Ross Droplet Technique . The method involvesdripping roasted beans with water before grinding them.
Why is this good? Think back to the last time you ground coffee in your electric grinder. Probably a large part of you was annoyed that the measured dose of coffee was smaller after grinding. Some of it stayed in the mouth of the grinder and some of it spilled all over the place. If you splash the beans with a little water, you minimize these problems caused by the static electricity that is generated during the grinding process.
Ross drops for more efficient coffee grinding
When you use an RDT and grind coffee, what happens is that...
- the grinding environment is more conductive and allows better dissipation of static electricity.
- The retention of the coffee grinder isminimized.
- coffee that would otherwise age in the grinder and affect further grinding.
- The dosing of coffee directly from the grinder is more precise.
- coffee particles do not form clumps, which would cause extraction problems.
Does it work? Measurements of mass-matched coffee batches on an EK43 professional electric grinder show that coffeeground without RDT has a higher retention than when using the Ross technique (with RDT 0.1 g, without RDT 0.3 g).
Does 0.2 g seem like a negligible amount to you? When making filtered coffee and using the aforementioned Mahlkönig EK43 it might be. However, if you don't have this super-grinder with one of the lowest retention values in the world and want to prepare espresso, then the difference in tenths of grams already plays a role here.
Prepare better with RDT with espresso
One thing is the grinder's retention. Another is the consequences of this process like coffee settling, which will age and negatively affect the next grind. Third is the effect of spilled coffee after grinding, which makes a mess and takes away from the original measured dose. Then there is the problem of coffee particle accumulation.
The charge created by friction during grinding forces some coffee pieces to stick together. However, such coffee particle relationships are not the best for good water flow through the coffee. The coffee lumps encourage the water to bypass them. The result is uneven extraction and an unbalanced taste of the coffee.
This phenomenon is called channeling or channeling. It can happen in both filter coffee and espresso. It is in espresso that the consequences are more pronounced and therefore more unpleasant. When a coffee lump is at the bottom of the portafilter cup, it can clog its perforations. This becomes a local barricade for the coffee to flow out.
In case you don't have good quality espresso baskets, this clogging problem can further increase the number of leaky holes. With precision cups like filters from IMS or VST , the perforation on the bottom is more precise and more numerous.
What to watch out for in RDT?
We know the advantages, now come a few caveats. Since this is a low-tech method of coffee pre-treatment, you can try it out for yourself right away. The ideal way to drip water onto the beans isusing aspray bottle. Spread the coffee on a plate or shake the beans in a bowl after gently spraying them.
Make sure you don't use too much water. Pptimum should be about 2% of the weight of the coffee. Thus, for a batch of 18 g of coffee, gently sprinkle it with about 0.3 to 0.4 g of water.Do this step right before grinding so that the moisture ratio does not change.
As the added water will touch the grinding stones in the grinding mechanism of the grinder, it is important to know their material. If you have agrinder with stainless steel stones, everything should be fine. Also remember that we are talking about the so called single dose coffee grind. Please do not add water to the full hopper of the grinder. ????