I am very new to the espresso-making world, and recently purchased a Krups XP1020 espresso machine. The machine makes decent espresso, but it has no crema... a very thin foam, at best. I have been experimenting with different grinds, pull times, and tamping pressure, but I have been unsuccessful. Does it have anything to do with the fact that it is a steam espresso machine, rather than a pump?

This brings back very, very old memories. 20 or 25 yrs. ago I had a Krups steam 'espresso maker'. I don't remember any crema on my espressos. I doubt it's possible on those machines, but I worked with preground coffee then. Perhaps freshly ground coffee makes a difference, but I wouldn't bet on it. I sold the machine after a few months because my Bialetti Moka gave better results. You can't steam milk with a Bialetti, though.

EDIT: I remember now why I sold it. The coffee frequently had a burnt taste, something I easily could avoid with my Bialetti. I think that the temperature was too high. As far as I know, the pressure generated by steam machines is on the (very) low side as well. Temperature too high + low pressure = no crema?

Basically, steam powered machines perform like moka pots (stovetop espresso machines). There is science behind it (and there are plenty of folks here who can explain it - I was an art major so won't), but steam cannot produce the pressure to push water into and through the coffee at 9BAR. A sealed vessel at 1.5 or 2BAR that bursts can propel an espresso machine across the room. I think a permit from a nuclear regulatory commission would be required for 9BAR...