Variable Extraction Speeds between First and Subsequent Shots

[Aidan_Steensma]

Hello,

This is my first post to HB so forgive me if I muck something up.

About three months ago I purchased an Andreja Premium and a 2nd hand Mazzer SJ. I've recently just got over a sour shot issue as a result of blunt grinder blades (very embarassing ) - now that I've gotten over that problem I've been attempting to tweak my shots and I have noticed that the first shot of the day always seems to extract slower (and better in fact).

For example, this morning the first double ran to about 29 seconds. Using identical grind, tamp, quantities, and roughly temperature, the 2nd and 3rd shots complete in about 21 seconds. Why?

Being an AP it has a pressure gauge and the first shot hits the correct pressure. I backflushed before this morning's session, but that didn't seem to do anything.

Any thoughts?

Thanks

Aidan

[malachi]

... and roughly temperature...

What is your temp surf methodology?

What are the flavour differences between the shots?

How are you grinding (per shot, per session, weighing beans, loading up the hopper)? Are you cleaning and purging the grinder at the end of a session?

[Aidan_Steensma]

What is your temp surf methodology?

What are the flavour differences between the shots?

How are you grinding (per shot, per session, weighing beans, loading up the hopper)? Are you cleaning and purging the grinder at the end of a session?

My grinding is fairly precise - I weigh the grinds in the basket to 0.1g accuracy. I grind per shot and clean/purge the grinder thoroughly after each session.

I've tried to keep the temp surfing consistent too. I do quite a long initial flush, which I know by experience gets me to the right level - I then follow the same procedure for each shot (10 minutes to prepare, 6-8 sec flush, 30 sec recovery).

As for flavour, I think that the faster shots are a little sour, although I can't quite recall whether I've had a sour slow shot. Assuming this is the difference, is it possible that slight drops in temperature leading to sourness could speed the shot up by 8 to 10 seconds?

[HB]

For example, this morning the first double ran to about 29 seconds. Using identical grind, tamp, quantities, and roughly temperature, the 2nd and 3rd shots complete in about 21 seconds. Why?

A couple seconds of variation isn't unusual, but eight seconds faster and sour indicates the extraction is proceeding apace. There's nothing you've indicated that would point to a mechanical issue, so channeling is the most likely cause. Do you have a bottomless portafilter to check? Also look over the Troubleshooting Checklist of Perfecting the Naked Extraction for other possible causes.

Assuming this is the difference, is it possible that slight drops in temperature leading to sourness could speed the shot up by 8 to 10 seconds?

No. Sourness is also caused by underextraction (pour too fast).

[MaxNach]

well, well, well...

I was just going to start a new topic about this very problem.

I have had the Andreja premium since February. It took me a while to get a hang of things like cooling flush, tamping, dosing, etc. but things were pretty good back in July.

At some point (not sure when) I started having exactly the same problem you describe. I did not get very scientific about it yet but my gut feeling is that this is not something to do with my routine. The extraction time of shot #1 is much longer than #2, #3, #4.

Could this be due to scale build up?

I am going to get in touch with Chris Coffee next week to see if they can help with it.

Max

[barry]

this probably has more to do with first shot being hotter than subsequent shots.

[HB]

Huh?!? You two both lost me. Scale and/or hotter brew temperatures can make the shot run 8 seconds slower? OK, I've never intentionally cooked a shot to see if the extraction was markedly slower. In any case, you can remove the "mushroom" to quickly check for scale:


From Sputtering e61 & HX scale build-up - Cured!

[barry]

cooler water passes faster; hotter water passes slower. eight seconds slower? maybe.

[MaxNach]

Barry and Dan,

Thank you both for your replies.
I do agree that the whole problem is quite confusing.
Especially so since it is a recent occurrence for me.

One angle I tried to approach today was machine cleaning.
I confess, I have been slacking off on backflushing with cleaner.
My cleaning routine changed from backflushing with Cafiza every four weeks to removing the dispersion screen and soaking/scrubbing with cleaner. Baaaaaaad idea.

I did a backflush session with Cafiza yesterday and the first flush came out looking like an oil change!
The difference between first and subsequent shots this morning was less than it had been for those past few weeks. So I have a feeling that crud buildup may have been the culprit.
Still, the machine was not clean (water flow looking brownish) so I cleaned it twice more.

Now when I taste the water coming out of the group, it tastes like hot water.

I'll let you know tomorrow if my problem is gone.

Max

PS: Oh yeah, my shots also taste better!