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Single dosing and retention

Oct 04, 2026

With a single dose grinder, you weigh out the beans for one cup at a time instead of keeping a full bean hopper. You can easily switch beans, the beans do not sit ageing in the hopper, and what comes out should weigh the same as what you put in.

What is single dosing?

  1. Weigh the dose in the dosing cup, e.g. 18 g.
  2. Pour in the beans and start the grinder. The Varia VS3 starts when the cup is placed on the magnetic dock, and the Fellow Ode stops by itself when the beans run out.
  3. Clear out the last of the coffee with the bellows or the knocker.
  4. Weigh the ground coffee and compare it with the dose.

Retention

Retention is ground coffee that stays in the grinder and comes out in the next dose. On a single dose grinder, it should be very low. Varia specifies under 0.1 g with RDT and under 0.2 g without, for a 10 g dose (VS3). A difference between the weight in and out is usually caused by coffee in the spout or by static.

Profitec states that weight deviations on the Twist SD54 are caused by coffee collecting in the spout. Use the bellows several times, tap the spout lightly and brush away residue.

RDT: a drop of water

RDT means lightly moistening the beans before grinding, which reduces static and therefore retention. Varia describes the method for the VS3:

  1. Spray 2-3 sprays from a small spray bottle (5 ml) onto the beans in the dosing cup.
  2. Shake so that the moisture is evenly distributed.
  3. Wipe away any droplets in the cup and pour in the beans.

It should only be a light moistening. Never pour water into the grinder. The manufacturers prohibit rinsing or immersing the grinder in water.

Bellows

The bellows push the last of the coffee out of the grinding chamber. For the Mignon Zero, Eureka specifies closing the lid and pressing the bellows 4-5 times after grinding. Varia recommends the bellows after every grind, Profitec a few pulses at the end. It also keeps the chamber clean between deep cleans.

Static and WDT

Static makes the ground coffee clump, stick in the spout and scatter outside the cup. It is often most noticeable when the grinder is new and decreases over time. Dry beans and dry winter air cause more static. What helps:

  • RDT as described above.
  • Grinders with built-in anti-static, such as the Varia VS6 (ionisation needles) and Fellow Opus.
  • Tap the dosing cup lightly before pouring the coffee over.
  • Distribute the coffee in the basket with a WDT tool. It breaks up clumps and gives more even extraction.

Cleaning single dose grinders is described in Cleaning your coffee grinder.

Barista & Espresso