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How to Adjust Coffee Strength

How to Adjust Coffee Strength

March 19, 2019

How to Adjust Coffee Strength & Extraction Percentage

I am often asked how strong our coffee should be brewed or how much should be put into a brewing device. I wish I had an easier answer like, “1 cup,” but unfortunately the issue is a little more complex than that. In this blog I will help you discover how to answer this question for yourself. Now, let’s get started!

When coffee grounds come into contact with hot water extraction takes place. The liquor is the combination of coffee and water and is what you drink or might refer to as brewed coffee.

Extraction Percentage

Ground coffee loses some of its final mass as it is dissolved and washed into the brewed coffee by the application of water. As a general rule of thumb, the best tasting parts of the coffee dissolve first and the least tasty parts are washed away last. Typically, you want to extract 18 - 22% of the coffee grounds into the final brew or liquor. It takes some fairly expensive equipment to measure the extraction percentage and is not something most people have the capacity to do at home. So, why am I going full-blown nerd and telling you this? Well, there are two reasons: 1) You can taste when coffee is either under extracted or over extracted and knowing the difference will help you dial in your brew at home. Under extracted coffee can taste sour, grassy, or grain-like, while over extracted coffee will taste bitter. 2) At Glory Cloud Coffee we are able to give you a brew extraction percentage (free of charge) if you simply bring your brew equipment to our facility and brew some with us. Simply contact us and schedule an appointment ahead of time.

What Affects Extraction Percentage?

Five main things in the brewing process affect brewing extraction percentage. They are as follows:

  1. Agitation - The more agitation or turbulence the higher the extraction rate.
  2. Water - The hotter the water the higher the extraction rate.
  3. Grind size - The smaller the grind size the higher the extraction percentage.
  4. Roast profile - The darker the roast the higher the extraction percentage.
  5. Contact time - The longer the coffee stays in contact with water the higher the extraction percentage.

While these five factors do play a role in the taste of your coffee and the extraction percentage, I recommend only changing the grind when trying to adjust the extraction percentage. For further information and recommendations on these variables you can visit my previous blog Brewing Coffee at Home.

Grind Adjustment

When a coffee is coarse there is less surface area for water to come across and extract. Therefore, the coarser the grind the lower the amount of extraction. On the other hand, the finer the grind the more surface area there is for water to extract coffee from the grounds. With that said, if you find that you need to reduce the extraction percentage of a brew because it is tasting bitter, then you would make the grind coarser. If the Coffee was tasting sour, grassy and grain-like you would want to make the grind finer.

Brew Strength

Brew strength is measured in a term called TDS or total dissolved solids. In the final cup or liquor you have a mixture of coffee and of water. How much of the liquor is comprised of coffee and how much is comprised of water is known as strength. For brewed coffee the optimal range for TDS is 1.15 - 1.35%. Again, this is probably not too important for those who are trying to brew coffee at home, but adjusting the brew strength will play a role in your final cup. Coffee that tastes too watery or weak probably has as TDS that is too low and coffee that has too much going on flavorwise (it can seem like there is a lot of concentrated flavors, but they are hard to differentiate because they are all jammed together) probably has a TDS that is too high. If you wish to know the TDS of your brew, you have a standing invitation to come to Glory Cloud Coffee with your brewing equipment and we will take a TDS reading using our coffee refractometer.

Brew Ratio

When trying to brew a great cup of coffee we want to use a brew ratio. That means that we have a weight ratio of water to ground coffee. In order to do this, we will need a scale. These can be bought inexpensively online or at a local store. When looking for a scale for coffee find one that measures in grams (preferably in tenths of grams). Typically, using a brew ratio of 1:15 - 1:17 (coffee:water) will allow us to get a great tasting brew with a TDS and extraction percentage that falls somewhere within standards.

While there are more factors that apply to getting a desired TDS and while the extraction percentage is closely tied to the TDS, I recommend trying to get your ideal TDS by adjusting the brew ratio. Provided all of the other factors are fixed and within the recommended spectrum (i.e. water temperature) this will most effectively change your TDS and brew strength.

Putting It All Together

Now that we have learned some theoretical knowledge about brewing coffee, let’s put it all together through some different scenarios:

  1. The coffee at my office has a very thin body and seems watery. What is most likely the problem?

Answer: There is probably a low TDS and the brewing ratio should probably be increased to include more coffee.

  1. You brewed coffee with a 1:16 ratio. The time of the extraction was too long and the coffee tastes overly bitter. What most likely went wrong?

Answer: Most likely there is too high of an extraction percentage. This could be changed by adjusting the grind of the coffee to a coarser setting. 

  1. You have used a 1:16 ratio to brew your favorite Colombian coffee from Glory Cloud Coffee but you notice that it is tasting sour, grassy and grain-like. What should you adjust?

Answer: Since it is too sour, grassy and grain-like that means the coffee is mostly likely under extracted or has too low of an extraction percentage, which means that changing the grind may need to be adjusted to a finer grind.  

For any questions you have about brewing or this article please feel free to reach out to me, Hayden, at:

Thank you so much!

Hayden Moore

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