I found myself with the day off and I did a small test.
Keep coffee, grid, dose, temp and yield fixed.
Coffee: Redbird espresso, froze at 7 days. thawed overnight. Opened and dumped into hopper 1/2 hour before this test.
Used a BDB with preinfusion at 6 seconds and preinfusion power at 70%. 197 degree temp. Used a bottomless portafilter and a BDB double basket.
Grinder is Ceado E6p V2
Measure tamping depth by tapping, grooming with tool lightly and hand tamping. Adjust puck tamper to the depth of the hand tamped bed and take measurement with vernier caliper from puck tamper.
1) Grind into portafilter. WDT with funnel and dissecting needle, groom to 10mm. x2
2) Grind into portafilter. Groom to 9mm, tamp to 11mm. x2
3) Grind into portafilter. WDT with funnel and dissecting needle groom to 10mm. x1
I pulled all shots consecutively, taking notes and setting them out to cool before tasting.
1) Both pulls were nearly identical in looks. Started at 7 seconds with a few drips, off center, that formed into a centered stream after about 3 more seconds. Dark, turning blond at about 25 seconds but still striping. 40 seconds to get to 30 grams for both.
2) Both pulls looked different but had similar issues. Started around 7 seconds and quickly formed into a single stream. The stream on both pulls was off center and had areas that obviously flowed faster from different sections. The fast flowing sections (assumed channels) were from different sections in the 2 different pulls. Blonding started earlier than the ones in #1 above. First shot took 36 seconds, second took 33 seconds.
3) Observations were same as #1 above but shot took 38 seconds to reach 30 grams.
I didn't let them cool to a uniform temperature. But I cleaned up while they all cooled and took a few sips of each. Tasing was not blind. They tasted mostly the same. In milk or water, i do not think I could tell them apart. The shots that pulled longer, #'s 1 and 3, were "juicier" with a more pleasing acidity, while the other shots had a sharper acidity. None were what I would call bitter. This is consistent with how I like and pull redbird. I like it pulled around 34-38 seconds with this dose and yield.
Still thinking about what this all means.