Why are pressurized portafilters bad?

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AlexKilpatrick

#1: Post by AlexKilpatrick »

I have been trying to get the best out of my Delongi KMix, almost as an experiment. (Have Breville Dual boiler on order). I upgraded to a Baratza Vario grinder, which has helped a lot.

I was having a hard time making anything other than wretched shot, and someone suggested I couldn't do a good job with a pressurized portafilter. I converted my PPF to non-pressurized, and it made a dramatic difference. I can make good (but not great) shots now.

But my question is "why?" I have a vague understanding of what a PPF does, but I don't understand why it makes bad espresso. My understanding is that a PPF is just a release valve that only releases when the pressure has reached a certain level. That seems like a good thing to me.

So why do they make espresso so bad? Is it possible to make good espresso with a PPF? I noticed just switching from a PPF to non-PPF made the espresso better, even when I didn't change anything else.

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Spitz.me

#2: Post by Spitz.me »

Pressurized portafilters do not rely on the coffee to create the proper resistance. The hole that opens up under pressure is very small which is why a coarser grind is needed to achieve a proper flow rate for a 30 second pull. The coffee grind you need to achieve 'good' results from a PPF is essentially an inadequate grind to achieve AWESOME espresso. A proper (?) espresso relies on grind fineness to create the resistance.
I know I've pulled a great shot when the flavour is 'like a beany taste that tastes like a bean'.

AlexKilpatrick

#3: Post by AlexKilpatrick »

Thanks. Trying to put this in my own words below. Is this right?

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Great espresso needs a fine grind.

However, using a fine grind with a PPF presents too much resistance to the water flow, making it impossible for the pressure valve at the bottom to open. The only way around this is to make the grind coarser, allowing the water pressure to build enough to open the valve. Unfortunately, this doesn't make good espresso because the water is not forced through the grinds.

The "advantage" is that the PPF will work with more traditional coarser grinds like you might get in pre-ground coffee at the store, or inferior grinders. Thus it is more likely to work with the grinders that "normal" coffee people have.

In essence, the PPF will make an acceptable espresso from a wider variety of grinds than a non-PPF. The trade-off is that it will never make a good espresso.

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Spitz.me

#4: Post by Spitz.me »

If your use of acceptable was meant to mean 'personally acceptable' than I agree with your conclusion. It's more like a different way of making moka pot coffee. They're really designed for the pre-ground espresso grocery store stuff and that stuff seems to be primarily designed for moka pots.
I know I've pulled a great shot when the flavour is 'like a beany taste that tastes like a bean'.

coffeedom

#5: Post by coffeedom »

Alex, you are pretty much spot on with your summary. A couple other things to note:

- pressurized portafilters or baskets are often used with preground coffee, which obviously compounds the issue. The resultant espresso, if you can call it that, is likely to be awful.

- the flow rates are almost always faster with pressurized baskets as compared to normal baskets, even if you updose. Finding a sweet spot of dose and grind to get a good flow rate is difficult. It's easy to get gushers or conversely to choke the machine with too many fines. But note that even if you choke a pressurized basket, that grind is probably still not fine enough for a regular basket.

- although flow is important, the real issue is being able to extract the emulsified coffee oils from the beans. This is what gives espresso its mouthfeel and intensity. To do this you need a relatively fine grind, something usually not possible in a pressurized setup. There is a range of grinds and doses you can use to achieve this, but all require a non-pressurized basket and a reliance on the coffee itself to get the right extraction parameters.

MerleApAmber

#6: Post by MerleApAmber »

Alex,
What Dom said here:
the real issue is being able to extract the emulsified coffee oils from the beans
is the intention, the practical matter is a restricted pressure relief venturi will absolutely change the physical structure of the oils as they are being accelerated and ejected into your cup. Using the puck and the fine mesh of the charge cup as your only restrictions help minimize the rough handling. :)