In hindsight, I have not been brewing my best cups of coffee lately. I noticed this when I brewed a cup of coffee with my new grinder. When I pushed my Aeropress down to decant the coffee into my mug, I noticed the plunger was much easier to push down. The plunger did not push too quickly; it felt just right.
Over the last few weeks, my Aeropress has been difficult to plunge. I did not think much of this because I have always known that some pressure is needed to brew with the Aeropress. I only realised there must have been an issue when I brewed with my electric grinder. I am using what looks to be a slightly coarser grind, although I cannot be sure because I do not have any grind measurement equipment and there is no universal language of grind size between grinders.
I was able to press this morning's Aeropress in around the same time as I usually do but there was a difference in the press. I no longer had to exert so much force to decant my coffee. I could press with a little bit of force and move the water through the bed of grounds. I now understand why Aeropress founder Alan Adler is able to push his Aeropress plunger with his arm. I probably would have hurt myself—or at least caused a bit of distress—if I had used my arm to plunge my Aeropress with my last grinder.
I also noticed this morning's cup of coffee was less muddy than previous coffees. I cannot confirm exactly what causes this but I believe the grind size to be a factor. My grind size is coarser which means that there are fewer small pieces (not necessarily fines, but on average the grind size is larger). Muddiness has been an issue in recent weeks. I had two or so cups of coffee last week where my last sip was incredibly bitter due to fines, similar to what you might find with the average French press recipe. French presses tend to create a muddier cup because they rely on a metal filter.
I looked up what may have caused fines to get into my cup. I was curious because the Aeropress uses a paper filter and I did not expect fines would be able to get through. Indeed, one of the reasons paper filters are so good is that they keep out fines. I arrived at the conclusion that the force I was exerting must have caused some fines to get past the sides of the filter. I reason this is true because I have noticed that if I do not put the filter on properly—if the filter does not fully cover the chamber—then fines tend to get through. I cannot suspect so many fines fines actually pass through the paper filter; they are not that small.
If your Aeropress plunger is difficult to push, it is a sign your grind is too fine. I did not adjust my last grinder much because I did not think to do so. It was only upon trying a coffee made with my new electric grinder at a coarser setting that I realised what my coffee could be. Maybe this is a lesson to me that I should push myself more. A big takeaway from James Hoffman's Best of Jim Seven book was that coffee should keep evolving. I should apply this principle to my coffee. I could have tried a different grind setting on my last grinder but I did not. Now I can experiment with the grind more easily on my electric grinder, I plan on trying a few different grind settings.