Category Archives: Maths

Extraction Uniformity and Channeling

For a while now I’ve been trying to understand the details of channeling in pour over coffee, and I found it very difficult to find a convincing description of why channeling (and thus astringency) happens suddenly when we grind a bit too fine, even if the surface of the coffee bed looks flat at theContinue reading “Extraction Uniformity and Channeling”

An App to Measure your Coffee Grind Size Distribution

[Edit April 20 2021: Chris Satterlee generously developed install packages for both OS X here and Windows here ! His full GitHub repo is here. I’m very thankful for this help (it’s not straightforward at all to do this).] [Edit April 25 2019: Please note this is not an iPhone or Android app, and IContinue reading “An App to Measure your Coffee Grind Size Distribution”

A More Accurate Way to Calculate Average Extraction Yield

I recently wrote about the detailed explanations and calculations behind the equations we use to estimate average extraction yield from coffee concentration (often called TDS) measured with refractometers. If you have not seen this discussion, I highly recommend reading it before you start reading this blog post, as it introduces a lot of the conceptsContinue reading “A More Accurate Way to Calculate Average Extraction Yield”

Measuring and Reporting Extraction Yield

Since I received the VST Coffee Lab III refractometer thanks to Vince Fedele’s generosity, I started logging the concentration (in % TDS) of every coffee I brew. This allows you to calculate the average extraction yield of your brew, which represents the fraction of your coffee beans by mass that was dissolved in your brewContinue reading “Measuring and Reporting Extraction Yield”

The Dynamics of Coffee Extraction

[Edit January 30, 2019: After receiving some feedback about this post, I would like to address a few things that I think were not clear enough. I’d like to thank Scott Rao for his comments. First, when I use language such as “over-extraction”, and “under-extraction”, I don’t mean that the associated extraction numbers are necessarilyContinue reading “The Dynamics of Coffee Extraction”

Statistics and Blind Tasting

A friend recently asked me a really interesting question about the statistical significance of blind tasting. He asked: “How many times should I successfully identify an intruder coffee by blind tasting among a set of three cups, in order for my experiment to be statistically significant ?“ As you might imagine, I really like thisContinue reading “Statistics and Blind Tasting”