I have a cheap Brix refractometer that I use for beer brewing and it works well for testing the original gravity of the wart before fermentation. I just tried to use it for pour-over coffee and the result seem a bit "optimistic" when it comes to extraction yield. I used the formula shared on this forum earlier this year by the user RapidCoffee.

The beans I used are Australia Skybury which I ground using a 1Zpresso JX Pro at grind setting #30. Here are the results:



I calibrated the refractometer before testing. In all tests I placed two drops of coffee on the sampling window and gave it a minute to settle before noting the reading. Although I used the diopter correction it was a bit difficult to clearly see the reading compared to the normal beer brewing range, likely because the lower reading of the coffee is on the edge of the view, where the optical quality of the lens is lower.

As for how the coffee tasted, I liked both of the Kalita results but was less fond of the V60. I followed James Hoffmann's method, but the result was more bitter than from the Kalitas.

Does the above test make sense? Should I bother testing other methods of brewing (e.g. espresso)?

Update: The above results are incorrect. I now measured the actual coffee liquid in the cup instead of water into the filter. I also re-calibrated my refractometer to make the 10 brix point the 0 point. This way the result is displayed closer to the center of the view, where the optical quality of the lens is a bit better. Here's what I got:



I think that 18.28 makes more sense for extraction yield.

boren wrote:I have a cheap Brix refractometer that I use for beer brewing and it works well for testing the original gravity of the wart before fermentation. I just tried to use it for pour-over coffee and the result seem a bit "optimistic" when it comes to extraction yield. I used the formula shared on this forum earlier this year by the user RapidCoffee.

The beans I used are Australia Skybury which I ground using a 1Zpresso JX Pro at grind setting #30. Here are the results:

image

I calibrated the refractometer before testing. In all tests I placed two drops of coffee on the sampling window and gave it a minute to settle before noting the reading. Although I used the diopter correction it was a bit difficult to clearly see the reading compared to the normal beer brewing range, likely because the lower reading of the coffee is on the edge of the view, where the optical quality of the lens is lower.

As for how the coffee tasted, I liked both of the Kalita results but was less fond of the V60. I followed James Hoffmann's method, but the result was more bitter than from the Kalitas.

Does the above test make sense? Should I bother testing other methods of brewing (e.g. espresso)?

Two things come to mind:
- something like 15:250 seems more like a brew ratio than an actual weighing of the output beverage weight. It's the latter number that you're supposed to use.
- At filter concentration, the coefficient is closer to 0.79 if you're trying to match atago/vst numbers. See

Which refractometer is it?

zefkir wrote:Two things come to mind:
- something like 15:250 seems more like a brew ratio than an actual weighing of the output beverage weight. It's the latter number that you're supposed to use.
- At filter concentration, the coefficient is closer to 0.79 if you're trying to match atago/vst numbers. See

Thanks for the pointers. I'll rerun my tests.

Jonk wrote:Which refractometer is it?

This one: https://www.amazon.com/Deal%E3%80%91Ori ... B077TVP5TV

Not that it makes a huge difference but your translation from Brix to TDS isn't quite right. 1.9 Brix is about 1.5% TDS and 2.0 Brix is about 1.6% TDS.

Makes a difference though- the calculations are wrong anyway because he's using brew weight and not Bev weight, but even without the fix its a 2% diff almost in extraction.

At a "gain" of roughly 2-3x for espresso, the readability/repeatability/accuracy of an inexpensive refractometer isn't bad to see "significant" changes in extraction, when comparing to your own data.

Even an Atago with a Magic is borderline for "drip" when you're arguably trying to hit a ±0.1% TDS "sweet spot"

culturesub wrote:Makes a difference though- the calculations are wrong anyway because he's using brew weight and not Bev weight, but even without the fix its a 2% diff almost in extraction.

That's true but it's just not a precise enough tool for measuring brew strength coffee. I bought one to fool around with for espresso but even for that I found it to be pretty finicky. I got it to compare pretty well to a few oven dehydrated samples but only if I filtered them first and also took pains to insure that the device and the samples were at the same temperature. Whenever I got just a little sloppy the readings were off significantly. I think a very careful technique is required to get consistent readings.