Hitting the Bullseye
It’s not always easy to hit the bullseye in coffee brewing. The examples from lesson 4.2 assume the target can be hit with a single grind change. Note that it may actually take a few attempts.
A Slightly Roaming TDS (The Pragmatic Option)
It’s a valid choice to reduce the beverage size when you notice slight indications of over-extraction. This subtle change is guaranteed to reduce extraction but will raise the TDS. Small TDS margins should be implemented allowing a barista to navigate easily. A change of 0.2% is fine. A change of 0.5% is too much. Given the average TDS of modern specialty espresso is around 10%, the 0.5% is a 5% change in strength.
Alternatively, cutting off the shot sooner also works. Based on BH espresso brewing experience, for every gram of water you add at the very end of the shot, expect a decrease in strength by approximately 0.1%. The longer the shot runs, the less strength the shot will have. However, if the length of shot affects your TDS by 0.5%, it becomes quite noticeable — assume a drop of no more than 5g in beverage weight as a working limit.