The flow rate describes the time taken for hot water to pass through the coffee grind, and eventually into the cup.

For any types of beverages that uses an espresso base, the flow rate would play a part in brewing or mixing it. This includes doing a pour-over.

This means that that only type of coffee making that don’t reference the flow rate is via the full-immersion method where the steep rate is used instead.

Because the how efficient water travels through the grind affects the flow rate, a finer grind will result in a slower rate, and a coarser grind resulting in a faster rate.

This is because the finer the grind, the less space is available for water to navigate it’s way through the portafilter basket.

In modern cafes, it is often said that a perfect espresso, or one close to it, would have a certain standard flow rate.

But that is simply not true.

I won’t mention that “standard” here as I don’t wish to skew you approach to making coffee.

So don’t make the mistake of focusing on a goal of fine-tuning the espresso machine and grind to achieve an exact ounce of espresso within a specific time frame.

It is also possible that a different flow rate is used for hot and cold beverages.

There cannot be a universal law on flow rate that dictates coffee making across all types of machines and coffee beans.

The coffee master or barista will have to test, practice, trail and error to achieve optimal or desired results for the coffee.