Ross Droplet Technique
The Ross Droplet Technique, or RDT, means adding a very small amount of water to a single dose of beans before grinding to reduce static. It can make grounds easier to collect, but it is only appropriate when the grinder manufacturer permits it.
What the research supports
Grinding creates electrical charge through contact and fracture. Moisture influences that behavior, and controlled research has found that adding water can reduce charging and clumping under the conditions tested. That does not mean every grinder needs RDT or that a particular number of sprays works universally.
The primary study, Moisture-controlled triboelectrification during coffee grinding, investigates these effects. Its results should not be converted into unsupported promises of fewer fines, perfect particle uniformity, or a fixed improvement in cup quality.
Check before trying it
- Read your model's instructions and any restrictions on moisture.
- Clean the chute and collection cup first.
- If the grinder has an ionizer, check its maintenance instructions.
- Keep water away from the grinder body, electronics, and controls.
Do not spray water into a grinder or dampen beans stored in a hopper. Where RDT is supported, apply only the minimal amount specified for the dose and grind promptly.
Compare a dry and permitted RDT dose
Use the same beans, grind setting, and input weight. Compare output weight, visible clinging, cleanup, and several brewed shots. If flow changes, dial in again before judging flavor. A spray bottle's output varies, so “one spray” is not a standardized measurement.
When to skip it
Skip RDT if the manual prohibits moisture, if the grinder is already tidy, or if damp grounds collect in the chute. The useful goal is a more consistent workflow, not another compulsory step.
Our static troubleshooting guide covers other checks, and grinder ionizers offer a different approach to reducing charge. Use a stable brewing recipe when assessing any change.
