I always thought that there were 3 types of pressure in contemporary espressomachines: 'spring'-lever, vibe-pump, rotary-pump. Today I hear from a friend, who visited a dealer that a lot of professional-machines are actually steampressure-machines (where the steam provides the pressure to make water go through the coffee). I told my friend that this method was used only in the beginning of espresso-history... but he has big faith in the dealer... and won't believe me...
He says that the pressure-boiler was not integrated in the machine, but located under the machine...
Any of you any thoughts about this?
thanks,
Michel