Final Answer:
If your shots are running shorter than 15 seconds, you need to adjust the grind to be more fine.
Step-by-step explanation:
When adjusting the grind of your coffee beans for espresso, the goal is to achieve the optimal extraction time, typically around 25-30 seconds. If your shots are running shorter than 15 seconds, it indicates that the coffee is being extracted too quickly, resulting in under-extracted and weak-tasting espresso. To rectify this, you need to adjust the grind to be finer. This means making the coffee particles smaller, which increases the surface area and allows for a slower extraction process. By doing so, you can achieve a more balanced and flavorful shot of espresso.
Adjusting the grind size directly impacts the rate of extraction. Finer grinds slow down the flow of water through the coffee puck, extending the contact time and allowing for better extraction of flavors from the coffee grounds. On the other hand, coarser grinds allow water to pass through more quickly, leading to under-extraction. Therefore, by making the grind finer when shots are running short, you can ensure that the water has enough contact time with the coffee grounds to extract all the desirable flavors and aromas.
In summary, adjusting the grind to be finer when your shots are running shorter than 15 seconds is crucial for achieving a well-extracted shot of espresso. It allows for a slower extraction process, ensuring that all the flavors and aromas are properly extracted from the coffee grounds, resulting in a rich and balanced cup of espresso.