title_body: Ideal Way to control shot extraction with Gaggia Classic
upvoted_answer: The best way to control of shot extraction without adding excessively complicated electronics (if by PID you mean proportional-integral-derivative controller) is:
  
  
  How fine is the bean grounding (the finer the grounding, the higher the density -> the slower the extraction).
  Applied pressure on the grounded beans in the machine group head (the higher the pressure applied (similarly) -> the slower the extraction).
  pressure and temperature are also important parameters to be concerned before moving to PID control (for example your extraction time/lenght could be longer but if the temperature of the water is low, there won't be excessive essential oil extraction).