Upper limit to portafilter size?

#1: Post by **pocojoe** » June 30th, 2019, 11:25 am

Hi everyone,

Would you be willing to share your thoughts on the scalability of espresso machine design? Specifically, I am wondering how scalable portafilters might be. My experience tops at at a triple basket. But, if you are trying to serve large groups of people would it be possible to make Americanos by the gallon if a properly scaled portafilter could produce a giant shot of say, 16 ounces of product?

My assumptions are that water pressure, and net flow rate of water per unit volume of ground coffee should be similar to current designs, but my question is should the thickness of the puck remain fixed, with the area of the bottom of the portafilter increasing linearly with increased shot volume? My intuition says yes, that making a very thick puck would change the dynamics.

Thanks for your thoughts - this is a serious enquiry.

Joe

It has been a while. It is good to be back!

#2: Post by **yakster** » June 30th, 2019, 11:40 am

Vintage espresso machines had a "hotel group" for brewed coffee, but I think it was more percolation and not puck based.

June 30th, 2019, 11:47 am

Burning Man Project...

#4: Post by **RapidCoffee** » June 30th, 2019, 12:52 pm

pocojoe wrote:I am wondering how scalable portafilters might be ... should the thickness of the puck remain fixed, with the area of the bottom of the portafilter increasing linearly with increased shot volume?

Short answer:
Probably.

TLDR answer:
If we regard espresso brewing as a form of column chromatography, then the puck height (but not the cross sectional area) has an impact on extraction. "In chromatography, peak width increases in proportion to the square root of the distance that the peak has migrated." (ref) In other words, increasing the column height by a factor of 2 spreads out the peaks by a factor of 1.4. So increasing capacity with a taller basket/puck should "elongate" the extraction.

This is a rough approximation, because espresso ain't exactly column chromatography. It's a variation in which the column itself is being extracted, for a relatively short period of time. This complicates matters with an extraction gradient in the puck (top layers extract more than bottom layers). But once again, this gradient is dependent on puck height, not cross sectional area.

Interesting topic. Welcome back!

June 30th, 2019, 3:13 pm

Thanks for the response. It follows my intution. I'll let the group knows how this works out. There are some very nice itsy bitsy pressure cookers on Amazon that better look out... I've got my eye on them!

Joe

#6: Post by **yakster** » June 30th, 2019, 11:27 pm

Check out Enrico of Italy, unsuccessful large portafilter on a home lever.

July 1st, 2019, 12:17 am

Interesting. Will try to avoid making the world's largest Mocha Pot.

I am going to get me a small (2 liter) aluminum pressure cooker and turn it into a portafilter.

It will be interesting.

Joe

#8: Post by **jyl** » July 2nd, 2019, 2:02 am

How about something like

OXO Good Grips Stainless Steel Potato Ricer https://www.amazon.com/dp/B00004OCJQ/re ... gDbBZWWV5B

As a starting point?

#9: Post by **C-Antonio** » July 2nd, 2019, 8:16 am

Form what I vaguely remember about the subject you will have to go with an increasily wider portafilter, proportion wise you will have to increase more in width than in height.
Then if you end with a wide portafilter, early coffee machine style, you will have to make a proper group with appropriate size showerscreen, good water distribution, and getting the proper pressure over the whole puck.
In creating an espresso machine for Polyphemus you will probably magnify also all the tricky bits of actually making a good espresso that have nothing to do with the machine per se'.
Have fun with your experiment, after all thats the point of tinkering.

#10: Post by **curmudgeon** » July 3rd, 2019, 3:07 pm

I'm curious to see what you come up with. I would imagine at some level, making sure you've got laminar flow of your water column would be beneficial, as this could encourage more even extraction across a large puck (I envision channeling will be a major issue). There are several homemade gadgets that can achieve that, but may not be up to the task at espresso temperature and pressure.