Editing Espresso machine (section)

===Steam-driven===
[[File:Wigomat-espresso-kaffeemaschine.jpg|thumb|upright|A steam coffee machine]]
A steam-driven unit operates by forcing water through the coffee by using steam or steam pressure. The first espresso machines were steam types, produced when a common boiler was piped to four group heads so that multiple types of coffee could be made at the same time.<ref name="timeline" >{{cite web
| url=http://www.cs.usyd.edu.au/~bob/Coffee/timeline.html
| title=An Espresso Timeline
| first=Bob
| last=Kummerfeld
| date=2011-03-14
| publisher=[[University of Sydney]]
| access-date=2018-07-30
| archive-date=2009-06-25
| archive-url=https://web.archive.org/web/20090625054808/http://www.cs.usyd.edu.au/~bob/Coffee/timeline.html
| url-status=dead
}}</ref> This design is still used today in lower-cost consumer machines, as it does not need to contain moving parts. Also, steam-driven machines do not produce as high a pressure for extraction compared with pump-driven. This results in the crema, a hallmark of an espresso, being of lower quality.