Why Weigh Coffee Doses After Using a Doser Grinder for Espresso?

A customer recently asked: "Why do you use a dosing grinder but, unlike some chain brands, not use the ground coffee straight after grinding? Instead you weigh it again before using it. Doesn't that defeat the purpose of having a dosing grinder?"

What Is a Dosing Grinder?

Before answering, let's first understand what a "dosing grinder" is.

A dosing grinder can set the weight of grounds to be produced, or the grinding time, for one session. As the customer says, it helps reduce the time we spend weighing coffee. But note: it reduces time, not steps.

We can adjust grinding parameters according to how much powder we need. FrontStreet Coffee, for example, needs 20g of coffee powder, so we can set the corresponding weight or time according to the grinder's function. FrontStreet Coffee's grinder runs on a timed function and needs 4.5 seconds to grind 20g, so the set time is 4.5 seconds. Convenient, yes. Now back to the customer's question: why do we still weigh the coffee?

Why Still Weigh the Coffee?

Although it can time and dose quantitatively, a grinder is often affected by other factors that shift the amount of ground coffee produced. A small deviation of 0.1g won't matter much, but the actual weight can often be off by 1g or more from the target. That forces us to use an electronic scale to measure the powder weight. There are three main factors that change the extraction weight.

1. Hopper Pressure

FrontStreet Coffee has discussed this separately before. Without a "popcorn preventer" - the umbrella-shaped device inside the hopper - the beans sit under pressure that varies with the quantity, and that pressure affects the beans about to be ground. More beans mean greater pressure and more uniform grounds; fewer beans mean less pressure and less uniform grounds. The same applies to the dosed weight.

FrontStreet Coffee ran an experiment: with a full hopper, 4.5 seconds ground 20g of coffee powder. With only 1/5 of the hopper filled, 4.5 seconds produced just 18.7g - a difference of 1.3g.

2. Gaps Between Coffee Beans

Think about how beans stack. Coffee beans are not equal-sized spheres arranged at regular intervals but irregular objects packed in a disordered way, so the gaps between them differ. That slightly affects timed grinders: because of these varying gaps, timed grinding inevitably produces small errors of about ±0.3g.

3. Residual Coffee Powder

When the grinder hasn't been used for an extended period, FrontStreet Coffee recommends first grinding 1-2g of coffee, discarding that portion, and then grinding the coffee needed for extraction.

That is because powder from a previous grinding session may remain in the grinder's channels. This residual powder not only causes dosing errors but also affects the espresso about to be extracted, since it has lost most of its flavor - think faster flow and uneven extraction.

4. Grind Adjustment

After you change the grind setting, the dosing changes too. Where 4.5 seconds once produced 20g, after you adjust finer, 4.5 seconds might grind only 18.8g; adjust coarser and the output rises. On top of that, at least 1-2 servings of coffee will be in an unstable state.

So, by now the reasons should be roughly clear. The main purpose of weighing again is to keep the gram weight accurate so it doesn't affect extraction, and second, when taste drifts, adjustments become easier. The convenience quantitative dosing gives us is that it removes most of the operating time - no need to keep staring at a timer and pressing pause.

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FrontStreet Coffee

No. 10, Bao'an Qianjie, Yandun Road, Dongshankou, Yuexiu District, Guangzhou, Guangdong Province

FrontStreet Coffee Recommendation

Accurate dosing only pays off if the bean is worth dosing. Espresso beans come in two broad types: the blends most cafes use first, and single origins chosen to taste, also known as SOE.

For traditional Americano and latte styles, buy FrontStreet Signature Blend or FrontStreet Commercial Blend. Both build on an old-school Italian recipe with a small amount of Robusta added, so extraction yields butter, nut, spice, dark chocolate and toast aromas - a wild, thick body together with the golden crema that makes latte art easy.

For espresso dominated by almond, walnut and almond-nut aromas, FrontStreet Signature Blend and FrontStreet Black Cocoa Blend come first, since both contain a large proportion of Brazilian beans, offering comfortable bittersweetness and creamy peanut aroma with a very smooth entry. FrontStreet Signature Blend adds the nut, chocolate and caramel notes and gentle acidity of Colombian coffee; FrontStreet Black Cocoa Blend brings the ripe-plum acidity of Yunnan small-lot, releasing a creamy chocolate aroma when ground, with a balanced, highly adaptable cup that works for latte and Americano as well as all kinds of specialty drinks - the best partner for a shop.

SOE, by contrast, emphasizes origin flavor. Single origins trace back to an estate or even a single farmer, which encourages better growing practices and higher quality. FrontStreet Sun-Dried Flower Queen SOE is a standout for its cream strawberry flavor, a gift of terroir and sun-drying: grown in Guji Hambella, Ethiopia, at altitudes up to 2,300 meters, it gives the cherries ample time to develop complex aromas, and natural processing lifts the sweetness. Roasted medium, it keeps the elegant floral and fruity notes while caramelizing gently, so a Flower Queen SOE Americano or latte carries cream, cocoa, berry, light floral and black tea. For a sweeter SOE, FrontStreet Costa Rica Blackberry SOE, a honey-processed single origin, gives blackberry aroma and clean sweetness; medium-roasted, it makes a bright Americano and, with milk, a latte with cranberry cookie, raisin and nut notes. For a low-acid, mellow, affordable choice, FrontStreet Brazil Queen's Estate SOE is a Yellow Bourbon of quiet sweetness; roasted medium-dark and pulled on an espresso machine, it shows butter cookie, macadamia and toast creaminess.