Filter paper shot forensics

Beginner and pro baristas share tips and tricks for making espresso.

#1: Post by GDM528 »

18g dark roast into to 18g VST basket.

AeroPress filter paper, precision cut to 55mm for the bottom of the basket, and 59mm for the top and mid-puck positions.

Wetted bottom paper / added half(ish) of grind and WDT'd / gently placed mid-puck paper onto grind / dumped in rest of grind and WDT'd / placed top filter paper and tamped firmly... *whew*.

Slow pressure ramp pre-infusion (maybe 20ish seconds). Started as a ring around the outermost holes in basket before progressing inward until puck fully wetted.

Shot pull went well. Freakily steady and uniform flow rate at 9bars all the way to 36g in the cup in about 25 seconds. Had exactly the bitterness I personally seek; underlying bright/sweet notes without any sourness - a nice shot for me.

The image below shows the filter papers extracted from the post-shot puck top/middle/bottom. Encourage y'all to 'read the tea leaves'.

Did the mid-puck paper save my shot from a mass-channeling event?


#2: Post by benhb »

Not sure on the middle paper (haven't tried it). Has adding that given you consistent improvements in shot quality/enjoyment?

Do you get bottom papers that are evenly colored (i.e. no areas where color is darker/browner than others)?

I've noticed on shots where there is color remaining on the bottom paper, that there was underextraction in those areas and the shot was less than optimal (notes of sourness and/or bitterness that are not pleasant).

Uneven extraction (& flavor faults):

More even extraction (good flavor):

GDM528 (original poster)

#3: Post by GDM528 (original poster) »

The mid-puck paper has consistently improved my shots: steady, even flow rates, and the results taste better. Unfortunately, it's fiddly process, so it's generally reserved for when I absolutely need to pull a good shot.

If you zoom into my mid-puck paper, you can see dozens of high-flow spots - some of which would have made it all the way to the bottom if not for the paper stopping it. I'm starting to think all my shots have channeling: the better shots distribute the flow across lots (100's) of channels, and the poor shots send the flow through only a few channels. The mid-puck paper might be a way to at least double the number of channels.

I have the least confidence in reading the color variations in the bottom paper, because the flow reverses when I flip the 3-way valve to end the shot. The bottom paper ends up taking an image of the liquid on the bottom of the basket that may not reflect the actual flow. That said, the good shot versus bad shot papers by benhb are remarkably telling!

GDM528 (original poster)

#4: Post by GDM528 (original poster) »

Pulled as 'sub-optimal' shot, and here's the evidence from the filter paper at the bottom of the basket.

Upper half of paper is darker, implying a tragic under-extraction of half the puck. I saw a similar pattern during pre-infusion, as the basket wetted - although not as pronounced as the coloration of the filter paper. Good remonstrator to pay more attention to tamping uniformly.

Can also see a dark spot in the paper just-left of dead-center, indicative of a channel. Ironically, a channel near the center of the puck fooled me into thinking I had a nice cone during the pull - ooops.