Eyeing an Aeropress brew. Note the wonderous dome shape of the grounds post-water, which doesn’t at all indicate a magical flavor but does comport to the Rao standard of spent coffee ground shaping. In short, it looks nice.

Starting small: My first days with the VST refractometer

If you’re reading this, you’re probably a bit familiar with coffee science in general and VST’s products. Most of us have read plenty about refractometers; some of us have used them on occasion, and a very few people use them regularly and have a thorough understanding of how they can make coffee brewing more repeatable and more traceable.

My first exposure to these tools on a practical level was a couple years back, when Jamie Cunningham and Derek Wolfe at Bongo Java Roasting Company of Nashville helped me calibrate my shop’s batch brew device. This was imminently easier than the brew-taste-repeat methods I’d used prior; we wasted much less coffee and got far better results in a fraction of the time. Now that I have one of these gizmos in hand, I have big plans to help us find the best doses and recipes for our espresso shots (both for drinking on their own and for mixing with milk), get us dialed in for distinct brew recipes on individual coffees, and just generally understand the variables of coffee brewing.

So far, I’ve opted to measure Aeropress brews. The Southeast Regional Aeropress Competition is at the end of the month, so I’m going to be brewing a bunch of these anyway — might as well use this as a learning experience, right?

Some initial observations:

  1. Aeropress is easy to overextract. My first surprise is that, of three brews today, every one of them has been in the 23–24% range, with TDS readings between 1.4 and 1.6. Each of these brews has been through a metal filter, and each has included minimal agitation; one was inverted while two were not; the total brew time on each was about 2:30 minutes. After the first brew, I decided to coarsen the grind some and pour normally instead of inverted; to my shock, the second extraction was even greater than the first. After cutting the brew time considerably — to about 1:30 — the extractions are back in the industry standard 20ish range.
  2. Overextraction is easy to taste. Were this a different coffee, I’d not be as sure about what I’m tasting. But so far I’ve been brewing Sunergos Coffee’s Ethiopia Worka, which I’ve had plenty of good cups of through other methods; the back of the tongue knows overextraction when it happens, although the digital data makes it easier to immediately recognize.
  3. Science is hard. Data, numbers, patience, records… this stuff simply isn’t my strong suit at all. And my life history to this point suggests a quick flame-out on collecting and sifting through data, but I’m convinced that the benefits of understanding coffee brewing more thoroughly will outweigh the initial burden of learning how to gather that understanding.
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