Basics - Extraction

Greetings, I'm the co-conspirator in this caffeinated quest.

Very simply, an espresso extraction works like this

• Water is drawn from a reservoir or water line and pressurised using a pump. 
• The water is heated to ~92 degrees Celsius in a boiler, a thermoblock, or a heat exchanger.
• The heated water is then forced at a pressure of at least 9 bar through the finely ground and tamped coffee until just before the shot begins to lose it's rich golden brown colour.

This should result in ~30 or ~60 ml espresso depending on the amount of grounds in the portafilter (single or double shot), and how they are tamped.

So that's some basic parameters we need to fit our machine into and some general targets to meet.