How do I know if I have the right grind size for drip?


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Feb 21, 2004
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I have a Baratza Solis Maestro Plus coffee grinder, which I use primarily for drip. I have a Technivorm MoccaMaster KBT 741.

I have been happy with the results, but I would like to know if there is any scientific or actual method of figuring out the correct grind size? I guess the same question goes for Espresso.

There are scientific methods to measure what is going on, but ultimately coffee is a sensory experience.

There are tests for total dissolved solids or TDS. TDS is a measure of how much coffee ended up in the water. The generally accepted ratio is 1.0 - 1.5% coffee to 98.5 - 99% water.

The exact coffee to water ratio is going to depend on the grind and the extraction (brewing) method. For each brewing method different grinds are appropriate. In general the more pressure, the finer the grind. In simplied model, French press has the most coarse grind because it has the longest brew cycle, more akin to steeping. Espresso has the most fine grind because of the high pressure short brewing cycle. For commercial and home drip brewers, a medium grind about the size of pre-ground pepper is about right. There are slight differences in ideal grind because of the configuration of the spray heads in the brewers.

For any of them, a uniform grind is critical. In our plant, we use $70,000 laser particle analyzers to ensure consistency of grind coming our of our $300,000 water cooled grinders. We grind differently depending on the application.

Our coffee experts can use the measurement tools to adjust the processes to a very fine degree to ensure that we've got the right grind for the application. Our equipment experts can choose the right brewing equipment and calibrate it to make sure that it is performing well. For commercial applications, the Fetco extractor series is great. Our field people can train our resellers how to use the equipment and keep it cleaned (delimed, etc.) They also do a lot with water quality, which also is a science. In general, 150 particles per million mineral content is best for coffee. There is target ph and so on.

Each step we can measure using a variety of tools. But in the end, does the coffee taste good? No machine can answer that.

I recommend SCAA Director Ted Lingle's book on brewing coffee.