Does flow of an excellent pull build slowly from center?

[brianneary]

Split from Uploading videos for HB by moderator...

I haven't made many videos in the past, but with Google Video it's easy enough and eliminates my bandwidth concerns. If you would like to occasionally upload a video for use on HB, but don't want the hassle of signing up, you are welcome to send me a private message and I'll do it for you (up to my e-mail box limit of 10M). I plan to do it more often.

As an example of the user interface, see Diagnosis of an espresso extraction with the Elektra A3.

Dan
I discovered your video a bit late in the game. And I have a question about it. I realize that the pull is to demonstrate an imperfection. But, does the flow in a excellent pull build that slowly and does it originate from the center?

Thanks
Brian

[HB]

It's hard to generalize about the speed with which a pour forms; they vary with the machine - especially rotary versus vibration pumps - and the "foamy-ness" of the blend. High crema blends will form what appears to be a solid pour more quickly and form a bulging cone too. Ristretto pours will obviously form more slowly given the slower extraction speed. This particular pour reveals its woes in the first couple seconds by the dead spot over the center extending to the left. Where the first second of beading begins isn't necessarily telling by its location (center, donut shaped), but whether it evens out in the following 2-3 seconds. If the pour doesn't "heal" itself by that point, it's likely that the extraction will be uneven - some areas going blond quickly (underextraction) and others remaining very dark brown (overextraction).