Published: Jan 30, 2017

VST:WTF Part 2

Now that I’ve covered what a refractometer is and how it works, it’s important to understand what it can and cannot do. There’s a lot of incorrect assumptions and opinions about these devices that I find myself constantly battling. Many baristas are understandably concerned about a device that might measure their effectiveness or replace their tastebuds. So this should set the record straight.

Here are some erroneous statements followed by my usual rebuttals.


“Extraction has nothing to do with the real taste of the coffee.”

Extraction is very very closely tied to the flavours experienced in a cup of coffee. There are many flavours in coffee that consistently occur alongside certain levels of extraction. You could call them extraction-specific or extraction-indicating flavours. When aiming to brew a coffee as well as possible, I’m trying to steer away from those flavours that indicate over or under-extraction. The result will be a well extracted coffee that’s true to the beans used.

When performing the same task with a refractometer, you can get to the same result faster, with more precision and accuracy (more on this later). In this case, the refractometer is helping you achieve taste-based goals; a long way short of “nothing”.

Measuring extraction does not tell you if a coffee tastes like citrus or milk chocolate. You might be able to get this kind of data from expensive gas chromatography, but I digress; “tasting” a coffee is not within the scope of a refractometer. That’s your job.


“I heard refractometers don’t measure anything meaningful. They’re just another toy.”

This couldn’t be further from the truth. As above, refractometers help you measure extraction, which is closely linked to flavour. There’s a couple of other insanely useful things that can also be garnered from this information:

Technique – if your grinds distrubution, pouring technique, tamping pressure or any other technique-related skills fall short, it can be detected by a refractometer. If you make two cups of coffee with identical recipes and equipment but differing techniques, the extraction will be higher when the technique is better, and lower when it is worse.

Roasting – More important and relevant than any color measuring device is the refractometer. It can tell you if a roast is under/overdeveloped, help you monitor consistency and aid the analysis of different roast profiles.

Equipment – Same experiment as above, put two products to the test by brewing identical recipes and seeing which gets the higher extraction. This works for baskets, tampers, grinders, burrs, showerscreens, pumps, espresso machines, pourover cones; anything that influences the way the coffee and water interact.


“We already make coffee well enough.”

No. You don’t.


“Taste buds are much better than a refractometer.”

Yes, they are. Taste buds are sensitive to an incredible array of flavours and are linked directly to your brain. They’re a marvel of biology, sensitive enough to detect a pinch of salt in a swimming pool. Hats off for taste buds.

The only problem with taste buds is that they’re attached to a human. An inconsistent, biased, emotional, volatile creature designed for anything but objective measurement of a liquid solution.

Refractometers are incredibly consistent, accurate, and precise. Three things we suck at. So why don’t we team up?

With a refractometer on your side, you become more consistent and accurate. Your off days can be detected, your preferences can be recorded and returned to, your prejudices can be exposed. Yes, your taste buds are better at tasting, but a refractometer is much better at not turning up to work hungover or with toothpaste in its mouth.


“I never agree with the results from refractometers.”

I doubt you could disagree with the refractometer. It doesn’t have an opinion. It’s much more likely that you disagree with the standards other people have applied to their coffees and shared with you. Perhaps you heard 18% extraction is the best, but you don’t like it when your coffee is extracted to 18%. Or maybe espresso above 8% doesn’t float your boat, but everyone else likes to drink it around 10%. That’s not you disagreeing with the refractometer, that’s you disagreeing with what others like.

Everyone should be using refractometers to measure the coffees they like to drink. Then, it becomes much easier to find that spot again. I like to think of it as a handrail. You can explore and move around the staircase, but if there’s a handrail you can always return to where you were.

You are absolutely entitled to your own opinion and preferences about coffee. What you taste is what you taste, no matter what anyone else says. The refractometer is a tool that can help you execute those personal preferences consistently; no one has to agree with them.

If you’re looking to get a refractometer, head to the US-based VST store or hunt down a local distributor from further down that page. I would recommend getting the refractometer, some spare syringes/filters and the iOS/Android app (which is now fully-featured with charts and recipe creation just like the desktop version). Start playing around, learning what you like and testing techniques or equipment. Your coffee will get better.


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