The Ross Droplet Technique — RDT — is adding a tiny amount of water to whole beans before grinding.
The problem it solves
Grinding generates static, and the finer you grind the more it generates. Charged grounds cling to the chute, to the catch cup, and to each other. That means retention, mess, and clumping — and clumps cause channelling.
How to do it
One spray from a mister onto the beans, or one drop of water stirred through with a finger. The beans should look barely damp and nowhere near wet.
Grind immediately.
What changes
Grounds fall loose instead of clinging. The chute clears itself. Retention drops noticeably. Static-driven clumping largely stops.
What does not change
The coffee. A drop of water against 18 g of beans is a rounding error, and the extraction is unaffected. This has been tested repeatedly by people hoping to find a difference.
Is it safe for the grinder?
For a domestic grinder used this way, yes — this is a long-established technique. What you must not do is soak the beans or grind genuinely wet coffee, which will make a paste in the burrs.
Do not do it with beans you are returning to a hopper. Grind what you wet.
Who benefits most
Anyone grinding fine for espresso, and anyone with a flat-burr grinder, which tend to generate more static than conicals.
Last reviewed 8 August 2026