by Abe Carmeli on Sat Sep 24, 2005 8:06 am
When I watch the bottom of the basket during a shot, I can clearly see an extraction pattern. For the longest time it was from the basket outside perimeter to the center. No matter which tamper I used. This issue came up before, with no clear answer as to what is causing it. One hypothesis was that it had to do with the pattern of water exiting the shower screen.
Only after getting the M3 grinder, I finally figured out what that was. I am now able to control the extraction pattern and change it by changing my leveling/distribution technique. Here's how it works:
An extraction pattern from the outside in (where the center of the basket is the last to saturate) is caused by what I call Schomer's Crater. Schomer advocates to control dosing as follows: Overfill the basket, do your NSEW leveling/distribution, and then shave off the access coffee with a bowed finger sweep across the basket rim. This movement will leave the basket surface with a shallow crater. As you sweep to shave off the access, your bowed finger pushes the coffee down where at the center of the basket it now becomes more dense than in the perimeter. (my guess, no density study done). Whatever the cause is, that technique always results with the center being saturated last.
To avoid the above saturation pattern, and reach simultaneous and even saturation across the basket bottom, one needs to leave the basket surface level without Schomer's crater. Now, that becomes a problem when you are dealing with a basket like the standard 14 grams Faema, and you do not want to updose. Most grinders will end up with 17-18 grams of coffee in the basket after leveling.
Here's where the Versalab M3 grindermade a difference in my case: It delivers fluffier grounds than the Mini. Those grounds occupy larger volume in the basket than grounds out of the Mini. Leveling the surface leaves 14-15 grams in the Faema basket, and as expected, the extraction pattern is simultaneous saturation.
There may be a way to do the same thing with a standard grinder (have simultaneous saturation without updosing). Any ideas?
Abe Carmeli