If you’ve visited us for coffee right at open in the morning, you may have seen this little dude on the countertop:
This is a coffee refractometer. Science-y. It’s a device that takes a sample of coffee and shoots light into it. Then, it measures how much the light bends due to dissolved solids inside the coffee sample. It then gives a reading of the TDS (Total Dissolved Solids) of the coffee. Essentially, it gives you a number that tells you how strong your coffee is.
For a shop like us that is obsessed with quality coffee, and especially consistent quality day to day, the refractometer is one of the most useful and important tools we own. It’s an amazing quality control tool.
Because of this, we use the refractometer every morning to dial in all of our filter (brewed) coffees. All three coffees on pour over and brewed and tested, and the batch brew is tested as well. This is one of the reasons why we are so proud of our batch brew and recommend that our customers try it. Honestly, it’s just as good than the pour over coffees at any given time. And it’s already brewed, so that’s cool.
When dialing in our coffees, we’re shooting for a TDS of between 1.38-1.43, which is on the slightly stronger side of normal for filter coffee. This is percentage of the sample. So yep, filter coffee is between 98.57% – 98.62% water. Using good water is really important for good coffee. That’s a rabbit hole for another time.
We like to think of the refractometer as a compass, getting us to the general area where a coffee tastes good, and then use our palette to find the exact right place where the coffee tastes best. We’re making adjustments to ratio (amount of coffee : water) and grind size to get the coffee to its sweetest, most complex presentation. We’ll taste a few brews with different ratios and grind sizes, and give samples to the other baristas opening for advice. We’ll then use the TDS reading and our sensory impressions to find the right specs for that day. We’ll write those specs down on a clipboard, and use them throughout the day. Then, we’ll do the same thing tomorrow. Most likely, due to a number of different variables, the specs will be slightly different.
It takes some extra time, but the assurance in knowing that our coffee tastes good, and is extracting the way we want, is more than worth it.