Did you know that in addition to the internal factors in making espresso shot, such as the set temperature or duration of the espresso shot and also external factors that affect variation in the quality of your espresso shot.
Whether the outside temperature or light. It all resulted in a change to your espresso shot, although internal control factors constant.
So the baristas who love espresso shot seriously need to keep practicing. The record of such external factors in order to analyze the quality or characteristics of espress shot every shot has to be adjusted to suit the external factors that you may not have complete control equivalent to internal factors.