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Johnny Randolph

The Beginners Guide To Measuring Total Dissolved Solids In Coffee

The Beginner’s Guide To Total Dissolved Solids And Coffee

By | Coffee

Have you ever heard someone at a café, cupping, or brewing competition throw out the acronym TDS and felt completely lost? The coffee jargon lexicon is lengthy and confusing at times, but we’re here to help breakdown the acronyms and fill in the blanks, starting with TDS. TDS stands for total dissolved solids, and in short, is our way to measure how much “coffee” is in our coffee.

To start, dissolved solids are the soluble parts of roasted and ground coffee that are dissolved and extracted by hot water and thus, make their way into our brew. Since water is a polar molecule, meaning it displays both negative and positive charges, it is particularly easy to bond with and dissolve into. This polarity allows water to easily attach to the various chemical compounds in coffee and extract them. Having two hydrogen atoms and one oxygen atom make the molecule uneven and ready to attach to another compound (coffee!) that might even out its molecular weight.

Stagg EKG pour-over kettle brewing over coffee grindsUsing TDS as a guide, we can determine how much of the coffee has been extracted. Then, with taste as our method, we can decide if we want more or less extraction during the next brew.  While coffee is approximately 30% soluble, for a long time, it was believed that coffee tastes best somewhere between 18%-22% percent. As the quality of the world’s coffees continues to improve, we are able to extract higher percentages with the flavor of the coffee still in the desirable range. Approximately 25% seems to be where the cut off point starts for specialty coffees. Each coffee is different and all coffees are constantly changing especially from the moment they leave the roaster.

How To Measure TDS

Unfortunately for your wallet, a device called a refractometer is required to measure the amount of dissolved solids in your brew. Refractometers for coffee can be somewhat expensive ($200-$1,000), but they are considerably cheaper and much smaller than a gas chromatograph coupled to a mass spectrometer, the other VERY fancy and scientific way of measuring dissolved solid. This magic tool works by measuring the deflection of light as is passes through the coffee. (Barista Hustle has a great article explaining this light bending property  further if you’re interested in nerding out a bit more.)

Along with your refractometer, you’ll need these items:

  • Distilled water
  • Alcohol wipe
  • Dropper
  • Paper towel
  • Small bowls or cups
  • Filtered syringe*

*Optional: If you are brewing using a metal filter like a Prismo or espresso shot, there will be suspended solids that are not water soluble. You will also want to use a filtered syringe to eliminate the suspended solids to get an accurate TDS reading. If you are using a paper filter, then your brew will be entirely dissolved solids.

How to measure TDS on a refractometer for coffeeStep 1: Set refractometer to zero using distilled water

  • Turn on your refractometer.
  • Add 3-4 drops of room temperature distilled water.
  • Take a zero set reading.
  • Wipe down refractometer lens with an alcohol swab.

How to zero out a refractometer for finding TDSStep 2: Put a small sample (around 2 oz) of well-integrated brewed coffee into a small bowl or cup

  • Make sure to stir the coffee to unionize the liquid. Stratified coffee will give you an inaccurate measurement.
  • Be sure to also allow the brewed coffee to cool to approximately 100°F or below. If you don’t have a thermometer, aim for room temperature or cooler.
  • If you’re using a non-paper filter, this is where you use the filtered syringe

Step 3: Take a small sample of  brewed coffee with a dropper or syringe

  • Place 3-4 drops of brewed coffee on the eye of the refractometer.
  • Close the lid and wait 10 seconds for the sample to reach a temperature close to the refractometer.
  • Press go and take a reading. Do this 2-3 times to ensure a proper reading.

Adding coffee to refractometer for TDS measurement

How to measure TDS on a refractometerStep 4: Use a clean paper towel to remove the sample

  • Wipe clean with an alcohol swab to reset for the next coffee sample.

For extra guidance during your first refractometer reading, check out this great video from Matt Perger of St. Ali and Barista Hustle.

Optimal TDS Readings For Different Brew Methods

For a pour-over dripper like Stagg [X] or Stagg [XF], the typical TDS measurement will be somewhere between 1.2-1.7 TDS. That’s right, your pour-over coffee is actually about +/- 98.5% water! For espresso-style shots with Prismo, we love the flavor most with TDS readings of 3.5-5.

Pour-Over: 1.2-1.5
AeroPress® Coffee Maker: 1.4-1.7
French Press: 1.4-1.7
Prismo: 3.5-5
Espresso: 8-12

Once you know the measured TDS, you can use a simple equation to determine the extraction percentage, which is the amount of coffee that it into your coffee.

extraction percentage equation for TDS

Ex: 320 grams of brewed coffee x 1.43 TDS = 457.6
457.6 / 20 grams ground coffee weight = 22.88
22.88 = your extraction percentage

How To Improve Your Brew Using TDS

The Beginners Guide To TDS and CoffeeThink of TDS as a tape measure for your brewed coffee. Did you take it as far as you wanted to? Did you take it too far? Using taste/flavor as the primary gauge, and then determining what level TDS tastes the best will allow you to know when you have reached the desired extraction level for a given coffee. Try your favorite pour-over using the same dose of ground coffee, brew style, and coffee-to-water ratio with three different grind sizes and see which you prefer. You can also try three different ratios (1:15, 1:16, 1:17) and see which one tastes the best to you. Remember, different coffees will taste best with different levels of TDS.

Are you ready to start using TDS measurements to fine tune your brews? Check out these great options: VST LAB Coffee III Refractometer or ATAGO Coffee Pal III. If you’re in San Francisco, you can also stop by the Playground for a brew demo. I can measure the TDS of your brew, and we can discuss how it may be improved. I also teach a Home Brewing class once a month. We’ll measure the dissolved solids in our brews and use taste/flavor to find the overall best version of the pour-over we are brewing. Find our Playground Education schedule here.

If you have any questions about TDS, feel free to email me at johnny@fellowproducts.com. I love to spend my time talking about coffee!

What Is Agitation And How Can It Make Our Coffee Taste Better

What Is Agitation and How Can It Make Our Coffee Taste Better?

By | Coffee

Agitation is defined as the action of briskly stirring or disturbing something, especially a liquid. An old can of paint, cake batter, and you guessed it, coffee, all benefit from the act of agitation. When we are brewing our coffee in the morning, it may seem counterintuitive to move, touch, or adjust the brewer of choice in any way, but by doing so we can use that agitation to help ensure that all of the ground coffee is exposed to water evenly. Ultimately, this provides a more even exposure of the ground coffee to water with the result being an overall higher extraction and ideally, a more balanced brew.

There are two ways that I have found are most effective to agitate the coffee slurry during brewing. First, gently stirring the slurry soon after a pulse pour with a spoon, or lifting the dripper or brewer and using a gentle 360° swirl. If you are brewing a “shot” with our AeroPress® Coffee Maker attachment Prismo, the stirrer that comes with the AeroPress works great. Since less water is used to brew a Prismo “shot,” there is more room to stir quite aggressively to achieve full saturation of the ground coffee. Swirling and stirring are both effective methods, and I recommend trying both to see which one you prefer. The goal with both of these methods is to expose all of the ground coffee to water as evenly as possible.

Adding agitation to coffee brewingSince Coffee is an organic substance, it changes as it ages from the date of roast. Can we get a similar extraction from a coffee that is three weeks off roast that we did when the coffee was eight days out of the roaster? Most likely not, but we can shoot for getting the most out of what is left. I have found that the same coffee at different ages off roast will taste better with different extraction percentages. Adding agitation between pours will help to more fully extract the compounds we have left in an aging coffee. Try adding agitation between each pour to get a full extraction if it seems your coffee isn’t tasting as good as it did when you first opened the bag.

Carbon dioxide also plays a role in our agitation choices. As you know because most likely, a “bloom” is part of your pour-over brewing ritual, roasted coffee contains CO2 and other gases. These gases are released much more readily when we grind the beans. Also, most electric burr grinders create at least a small amount of static charge when grinding coffee. Those gases, as well as any static from grinding, can cause parts of the ground coffee to become hydrophobic, or in other words, the coffee repels or fails to mix with water. We want to make sure that these pockets of the coffee bed that are more resistant to water get saturated as well. This is where the agitation really helps us achieve a full extraction.

Consistency is also key when determining how much additional agitation may help with getting an ideal brew. Are you doing five pulse pours total? Try lifting and swirling the dripper or stirring the coffee slurry after the bloom, after the third pour, and after the final pour. If you want more extraction, add a stir or swirl after the second pour. Want less extraction? Try only agitating the bloom and final pour. Allowing for room to move in either direction will help to narrow down which brew tastes best with given coffee and give you a consistent method and recipe to start with on any new coffee.

Ready to add agitation to your pour-over routine. Below is my favorite recipe using Fellow’s Stagg [X] Pour-Over Dripper to brew a 10-ounce cup of coffee:

Stagg [X] Pour-Over Dripper With Agitation

20 grams medium to fine ground coffee
340 grams of 205°F water
1:17 ratio

Benefits of agitating coffee bed during pour-over brewing1. Pre-wet entire paper filter with a pour-over kettle such as our Stagg EKG.

2. Dump out rinse water from brewing vessel.

3. Add ground coffee into the Stagg [X] Dripper, then gently lift and shake the dripper to level the coffee bed.

4. Start with the bloom. Add 60 grams of water to the coffee bed.

5. Lift the dripper and swirl gently a few times in a clockwise direction.

6. Add a second pour of 100 grams reaching a total weight of 160 grams.

7. Add a third pour of 60 grams reaching a total weight of 220 grams.

8. Lift the dripper and swirl gently in a counterclockwise direction.

9. Add a fourth pour of 60 grams reaching a total weight of 280 grams.

10. Add a fifth pour of 30 grams reaching a total weight of 310 grams.

11. Lift the dripper and swirl gently in a clockwise direction.

12. Add a sixth and final pour of 30 grams reaching a total weight of 340 grams.

*Total brew time should be between 3:00-3:30 minutes.

Give our agitated Stagg [X] Dripper recipe a try and report back. Do you have a favorite method of agitation we didn’t touch on? Drop us a line on Instagram. We love talking shop almost as much as we love drinking coffee!