If the engineer in you is wondering why...

by Reiss Gunson on Thursday, 19 January 2012 00:22

Everyone talks about running their Olympia Cremina at or around 0.8 bar, and if you're struggling to reconcile that with other machines running around 1.1 bar or thereabouts, there is an explanation although its a bit ugly.

Unfortunately the 'onboard' gauge on the Creminas seem to under-read by about 0.2 bar when a precision pressure gauge is fixed to the boiler of the Cremina.  The gauges on all machines do not under-read by 0.2 bar unfortunately, I have seen some where the differential is 0.3 bar and others where it is about 0.15 bar.  I have not yet found a machine the over reads and I've been fortunate to be able to check quite a few.  I know of one recently made machine that was in perfect agreement, and I am trying to find out why this is, having ordered a replacement mater pressurestat and gauge for our Cremina to see if the latest gauges are more accurate for some reason (calibration?).

So there you have it.  Your Olympia that mysteriously makes great espresso at an indicated 0.8 bar is most likely to be running at just over 1.0 bar, which should satisfy the engineer in you as it doesn't make sense that the correct pressure should vary so much between machines.

This is why we think it is important to talk about indicated pressure if you are referring to pressure indicated by the on-board gauge on your espresso machine.  Generally these gauges are not the most precise known to man, but they serve to give an indication.  Once you know your machine and gauge, the actual pressure is less relevant, you just come to know that at an indicated pressure of 'x' your espresso tastes good, and much below or above that number it doesn't.

« We finally upgrade our October 2003 Olympia Cremina so the mater pressure-stat sits up the right way A big thank you, whether you're enjoying Londinium Espresso in the sun or the snow this January »