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Pressure at the pump is not that relevant. What is relevant is the pressure at the point where pressurized water meets the coffee puck. And this pressure very m
by menaerus 4y ago
Pressure at the pump is not that relevant. What is relevant is the pressure at the point where pressurized water meets the coffee puck. And this pressure very much depends on multiple factors but let's say that the coffee ground level is one of the most important things. If you have a pump pumping water at 15 bars but you have a very coarse ground coffee in your basket, resulting pressure is _not_ going to be 15 bars. Similarly, if you grind the coffee at very fine levels then the resistance of the coffee puck will increase and therefore resulting pressure might very well end up being _more_ than 15 bars.
That said, another thing which plays a big role in the resulting pressure is the design of the brewing head and the design of your basket. Baskets can be either pressurized (they have a single hole through which the coffee will flow) or non-pressurized (they have a lot of small holes through all of which coffee will flow). You can imagine that the resulting pressure will depend on the type of the basket you're using.
Because cheaper appliances will by default use pressurized baskets, they will tweak the pump to some pressure level which they found to work the "best" for their type of machine and that level is exclusively much more than expected 9-10 bars. Nespresso will for the same reasons do the same with the difference that they make one step forward to take over the full control over the puck preparation process through their prepackaged pods.
- pier25 4y agoDoesn't the OPV release any excess pressure above a certain setting?
- menaerus 4y agoOPV machines sure but I was referring to appliances in the field. I don't think these are OPV capable?
- pier25 4y agoEven the Gaggia Classic has an OPV, and it's an entry level machine.
- menaerus 4y agoOk, what's the point you're trying to make? In the early beginning I have had DeLonghi and it most certainly didn't have any OPV.
- pier25 4y agoWell you made some statements in your previous comment about pressure which suggested they were generally applied to espresso making. That simply isn't true. Espresso machines without OPV are really a minority. Even single-boiler entry level machines like the Gaggia Classic or the Rancilio Silva have an OPV.
- theGnuMe 4y agoWithout a pressure release, they might explode right? Seems bad, I would expect it to be standard equipment.
- menaerus 4y agoThey are not going to explode but on such machines if you remove the portafilter straight after extracting the espresso, the puck will "explode" and is going to create a mess. In more expensive machines this is regulated through OPV and solenoid valve through which the pressure built up is going to be released.
- menaerus 4y agoParent comment seemed to suggest that (much) higher pressure produces better espresso and my comment had a sole intent, at the expense of simplifying some things, to give some grounds why espresso manufacturers might use higher than 9-10 bar pressure at the pump. Gaggia Classic is a 350 EUR machine whereas Rancilio Silvia is 600 EUR machine. These are not entry level machines. They are entry level for someone becoming more interested in espresso but not for ordinary people. And ordinary people do not spend 400-500 EUR for a coffee machine if they think they are going to get the same for twice less money. Twice less money machines do not have OPV.