Post #2074: Coffee chemistry Christmas, part II: Aeropress.

Posted on January 5, 2025

 

On the path to coffee snobbery, there is no better starting place than Walmart.

That’s where I just bought a made-in-USA Aeropress single-cup coffee maker.

In the end, coffee is all about chemistry.  Chemistry and physics.   Chemistry, and physics, and ruthless efficiency … and an almost fanatical devotion to the Pope.


The back story …

I abused the fancy coffee that I was given for Christmas.

I did that by putting it in a coffee maker, and brewing coffee from it.

I got bad, bitter, burnt-and-ashy coffee each time.

I now realize that’s because the fine coffees I was given were ground too fine for the coffee makers I had.

Source:  Bunn Coffee Basics Brochure (.pdf).

You only need this graphic, from the Bunn Corporation, to understand that you shouldn’t use really finely-ground coffee in equipment that takes a long time to brew the coffee.  (Note that I did not say “can’t”.  I proved that I can, just above.)

 

Source:  Bunn Coffee Basics Brochure (.pdf).

If you do, you’ll “over-extract” that finely-ground coffee, and so get too high a dose of whatever it is that makes coffee bitter.  The bitter stuff comes out of the coffee more slowly than the more desirable flavors do.

The upshot is that if you take coffee ground so fine that it should take less than a minute to brew it, and instead brew it for eight minutes, you end up with too much bitterness.  Much too much of the products of the “3rd phase” of extraction, above.

Too much bitterness accurately describes what I got, using two different methods, no less (Mr. Coffee, and Melita pour-over.)

There are several coffee brewing methods that work with finely-ground (fast-extracting) coffee, that a) either get the coffee brewed pronto, espresso-style, or b) just expect you to drink incredibly bitter coffee full of coffee grounds.   Discounting b) (e.g., Turkish coffee), of what was left, everything required unique equipment (e.g., moka pot), but Aeropress stood out, for a lot of reasons.

First, it’s not an espresso machine.

Second, it’s not an appliance at all.  No electricity.  It’s just a well-designed coffee press.  You have to heat the water in something else.

Third, doesn’t take up much space.

Fourth, it’s made in U.S.A.

Fifth, cleanup is a snap.

Sixth, it makes good coffee.

But.

But it only makes a mug of coffee at a time.

Name-brand paper filters for it cost 3 cents a mug.  (There are non-disposable metal-screen-type filters, but E-Z cleanup with disposable paper filters is a big part of the attraction for me.)

And the device itself seems expensive for what you get ($35 at Walmart).

And, to be clear, it’s more fuss than dumping coffee and water into a Mr. Coffee.  In particular, you can’t just come back and pour yourself a second cup from the pot.

But I only had to use it once before I said, whatever rake-off these guys are getting for this device, they deserve it.  This thing works well, and does exactly what it’s supposed to do:  Brew a nice cup of coffee, from finely-ground coffee.


Time out for a cup of coffee with the Aeropress

I’m an upside-town Aeropress user.  That is, I stand the device in its head, with the filter opening at the top.  Spoon in the coffee.  Add the water.  Screw on the filter housing.  Brew, briefly.  Then invert it onto a mug and press out the brewed coffee.

It’s not rocket science.

Above, as packaged at Walmart.  The box on the right is a pack of 350 disposable paper filters.  The right cylinder slides within the left, with the black foam end cap forming an air-tight seal (like the plunger of a hypodermic.)  The filter holder twists onto the end of the left cylinder.

Below, left to right:

  1. A scoop of finely-ground coffee, into the upside-down Aeropress.
  2. A cup of hot water.
  3. Hot water on the grounds.
  4. Twist on the filter paper and holder, wait 30 seconds.
  5. Invert over your mug, and press out the coffee.
  6. Coffee.  And the Aeropress re-inverted, filter cover removed, showing coffee-ground-and-disposable-filter “puck”.

 

Post-puck-plunger, pre-post sink rinse.

The big advantage that an Aeropress had is that it isn’t an espresso machine.  It’s just a little plastic coffee press that uses disposable filter papers and seems to be exceptionally well-engineered.

And, importantly, produces drinkable coffee from finely-ground coffee.

Where does Aeropress stand, in terms of the fineness of grind it prefers?  Not quite as fine as espresso, but not far from it.

Source:  Baratza Encore coffee grinder manual.

I don’t think the numbers above represent any physical units.  Nor do I think this particular coffee-grind scale is linear in any obvious dimension of the resulting ground coffee.  It’s just the readings that show on this particular brand of coffee grinder.  All I’m just saying that Aeropress is on the espresso end of the fineness scale.

And that matches the coffees I was given for Christmas.

 


Conclusion

 

At this point I’m supposed to ooh and aah over the taste of the Aeropress-made coffee.

While the Aeropress does make a good cup of coffee, from finely-ground coffee, it’s still — how can I put this? — coffee.

Perhaps I lack the aesthetic refinement of the true coffee snob.  Perhaps I just need more time to fine-tune my technique with the Aeropress.

Or maybe I just don’t like coffee all that much.

In any case, I remain a coffee satisficer.  I can definitely tell when I’ve brewed a bad cup of coffee.  As I did, by brewing up my finely-ground gift coffees in my Mr. Coffee.  Or earlier, when I failed to de-scale my Mr. Coffee.

But those same gift coffees produce perfectly satisfactory coffee, when brewed in an Aeropress.  The results fall well within the broad range of what I consider to be acceptable coffee.  And so, the Aeropress is a success, in that it gives me a way to make decent coffee, from the finely-ground coffees I was given at Christmas.