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

This is a question from a customer: "Why do you use a dosing grinder but, unlike some chain brands, don't use the ground coffee directly after grinding? Instead, you weigh it again before putting it to use. Doesn't this defeat the purpose of having a dosing grinder?"

What is a Dosing Grinder?

Before answering this question, let's first understand what a "dosing grinder" is!

A dosing grinder refers to a grinder that can set the weight of coffee grounds to be produced or the grinding time for one session. As described by the customer, it helps us reduce the time spent weighing coffee. However, it's important to note that it reduces time, not steps!

We can adjust grinding parameters based on the amount of powder we need to use. For example, FrontStreet Coffee needs to use 20g of coffee powder, so we can set the corresponding weight or time according to the grinder's function. FrontStreet Coffee's grinder operates on a timed function, requiring 4.5 seconds to grind 20g of coffee. Therefore, the time it sets is 4.5 seconds! Yes, it's indeed very convenient! Now let's return to the question raised by our customer: "Why do we still need to weigh the coffee?"

Why Still Weigh the Coffee?

Although it can time and dose quantitatively, many times, grinders can be affected by other factors, causing deviations in the amount of ground coffee produced! While small deviations of 0.1g naturally won't have too much impact, often the actual weight can deviate by 1g or more from the expected amount. This forces us to use electronic scales to measure the powder weight! There are three main factors that cause changes in extraction weight!

1. Hopper Pressure

FrontStreet Coffee has discussed this issue separately before. Without a "popcorn preventer" (an umbrella-shaped device inside the grinder hopper), the beans in the hopper will form different pressures depending on the quantity. This pressure affects the coffee beans about to be ground. More beans mean greater pressure, resulting in more uniform ground particles; conversely, fewer beans mean less pressure, resulting in less uniform ground particles! The same applies to quantitative weight!

FrontStreet Coffee conducted an experiment: with a full hopper, 4.5 seconds could grind 20g of coffee powder. However, with only 1/5 of the hopper filled, 4.5 seconds only produced 18.7g of coffee powder - a difference of 1.3g.

2. Gaps Between Coffee Beans

Let's understand the stacking principle~ Because coffee beans are not equally sized spheres arranged at regular intervals, but rather irregular objects arranged in a disorderly manner, the gaps between each bean are different. This slightly affects timed grinders! Because of these different gaps, timed grinding will inevitably produce slight errors (±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 powder, discarding this portion, and then grinding the coffee powder needed for extraction!

This is because there's a chance that coffee powder from the previous grinding session will remain in the grinder's channels. This residual powder not only causes dosing errors but also affects the espresso parameters about to be extracted due to having lost most of its flavor (faster flow rate, uneven extraction, etc.)!

4. Grind Adjustment

After adjusting the grind setting, the dosing will change! Originally, 4.5 seconds could produce 20g of coffee powder, but after you adjust it finer, 4.5 seconds might only grind 18.8g! If you adjust it coarser, it will increase the output! Additionally, at least 1-2 servings of coffee powder will be in an unstable state.

So, I believe everyone now roughly understands the reasons: The main purpose of weighing again is to ensure the gram weight is accurate and doesn't affect extraction; secondly, when taste deviations occur, adjustments become more convenient! The convenience that quantitative dosing brings us is that it eliminates most of the operation time - no need to keep staring at the timer and pressing the pause button!

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FrontStreet Coffee

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

Important Notice :

前街咖啡 FrontStreet Coffee has moved to new addredd:

FrontStreet Coffee Address: 315,Donghua East Road,GuangZhou

Tel:020 38364473