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Ross Droplet Technique (RDT)

Ross Droplet Technique (RDT)

There’s nothing more frustrating than seeing grounds stuck to the edge of the chute and the resulting decreased coffee weight on the scale. It’s especially annoying when you don’t have a bellows to blow out all the trapped coffee inside the electric coffee grinder. There’s no other choice, you’ll have to load another round of beans until you get the right amount of ground. 

Coffee Retention due to Static


Furthermore, it also indicates you’ve probably some of your last grind, in your current dose. That’s definitely going to have an impact on your brew in terms of flavour and aroma. It’s even WORSE if you were in the middle of dialing your shot. You’re more than likely going to have to run a round of beans to clear as much as possible, so that the particle sizes are uniform during your pull.


One of the reasons coffee grounds get stuck throughout the grinding process is the generation of static electricity. The main mechanism of static is via a concept called friction! Something you probably have experience with. Just in the same way you’ve accidentally ‘shocked’ yourself after walking on carpet.


As beans move through the burr chamber, they pick up an electrical charge that causes the ground coffee to get stick together and clump against insides of the machine.

Furthermore, weather can have an impact on static charge build-up. Particularly when the weather is dry, so may notice more clumping during winter when the humidity has dropped.


Now that we’re done with the technical explanation of one reason of why not all the grounds are moving through your grinder, let’s go onto an easy solution that anyone can implement immediately!

Apart from investing in a single dose third-party attachment piece and bellows from Etsy, you can give the Ross Droplet Technique (RDT) a try.


A simple method of adding a single droplet of water to your beans before grinding to reduce static and reduce the amount of retention in your grinder as shown below.


Coffee Beans on Scale 

Weigh your beans out as per usual


Water Spray into Coffee Beans 

Hit it with ONE spray of water


Bean Shake 

Shake the beans


Coffee Ground Pre-RDT 

Ground bean weight without RDT


Coffee Ground Post-RDT 

Ground bean weight with RDT


Not perfect, but much better than without the RDT. Give it a try! You don’t need any fancy spray, just any cheap plastic or glass one will do. Here's one from Target in Australia: Click here.

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