I've been using my Breville 920XL for nearly a year and seem to have tamping, grinding, and shots down.

The only problem I'm having is that every time I start the machine and pull shots, the first one would be perfect and subsequent shots will start to go downhill.

I pull 1:1 ratio 18g in and 18g out, consistent tamping, same grind settings, same temperature, same pressure, same beans, however, the following would happen:

1st shot pulls in at around 28sec. for 1:1 ratio.
2nd shot 26sec.
3rd shot 24sec.
4th shot 22sec.
5th shot 20sec.... etc etc.

I clean my machine and do the tablet & backwash on a regular basis. I even tried the supplied rubber to test the pressure and all checks out fine.

Anyone experience this? Could this be a problem with the machine? The next day, the shots would be just the same, 1st one perfect and the next would be less.

How's the taste? I know the shots are running faster, but how is the taste changing?

Also, how quickly are you pulling these shots? When I would be pulling several shots on my 920xl and Baratza Vario in semi quick succession the grind from the Vario would start to wander and loosen up and shots would run fast, which generally required minor adjustments to the grind setting over more than 3-4 shots. Sometimes the change would be quite drastic like you mentioned and would typically be back to normal the following day. I've never had the same issue with my monolith. I can only guess but it seems like the grinder settings are being impacted by heat buildup or something similar.

What happens if you pull a shot then come back 15 minutes later? Is there any change?

*sigh* Thanks for your reply.

Interesting!! I never thought about the fact the Baratza Vario may be the problem... assumed it would be perfect.
Taste would be less strong compared to the shots prior.
I'm pulling the shots about 2-3 minutes apart as I take my time in preparing the bed for tamping.

I'll try what you've suggested regarding heat buildup and see what happens after 15min or so cool down.

Yeah, let me know what you find out. The 15min should be a bit of an exaggeration, but clearly something at some point from day one to day 2 is "resetting" so hopefully that will narrow down how long it is before that happens which might help locate the problem. I just always noticed the issues when I had people over and I was making 4-5+ drinks in a row (not face paced but only a few minutes in between). If I was making a coffee for myself and only pulled 2-3 shots it was never noticeable enough.

Have you tried a short flush between shots?


Randy

yep, I always flush between shots to clear any grounds out that had been left behind. I've had zero issues since I got my monolith and didn't have any while I was trying out my cousin's K30. The Vario did it pretty regularly and with various coffees, even after cleanings and calibrations, so it's my best guess as to the cause (at least in my situation). Not to bash the Vario, it got me a lot of great shots over the 2 years it was my primary espresso grinder and with some grind adjustment on higher shot days kept up just fine.

I also have the same experience with a Vario. Not noticeable if I leave 1 hour between shots, but I did notice a slight effect with 10 minutes between shots (although that could've been inconsistent puck preparation). I've definitely noticed it in the past when I've had to make 5+ shots at a time.

Crazy theory: perhaps burr rotation heats up the (plastic) burr carrier causing expansion, thus reducing fineness? I wonder how much of a height difference one notch actually corresponds to...

(My grinder is quite new, although it's the Mahlkoenig Vario home version, built in Switzerland - not built by Baratza.)

Try grinding back to back, but swap the order of the grinds that you used when pulling the shots. If the grinder is the issue, you should see your second shot (with the first grind) taste better than the first shot (with the second grind). If the second shot is still worse, then maybe your 920 is not recovering heat fast enough (which would be a defect).

1. Grind your first dose into a small cup (A)
2. Grind your second dose into another small cup (B).
3. Prepare your first shot using the second dose (cup B).
4. Pull the shot -- taste.
5. Prepare your second shot using the first dose (cup A).
6. Pull the shot -- taste.

I've seen some references elsewhere to warmer grinds leading to a faster extraction. (That person was talking about the puck being in the machine for some time before switching the pump on, i.e. heating inside the portafilter - which I imagine heats more than a grinder would.) That seems like a more likely explanation than my burr holder expansion theory .

I wonder if one could modify the Vario to add a fan. Maybe I'll try to find some thermocouples first to measure burr temperatures too (maybe I should just measure the grind output temperature).