Watery start to extraction
I've done a bit of a search but couldn't find anything related to my problem...
I'm a bit out of practice, have not made a coffee in months. I'm on the machine this morning, and i seem to keep getting shots that start weak and watery, before thickening up to look like they should.
Literally the first 5 seconds of the shot comes out with a transparent, thin, brown liquid (like you might get at about the 50 second mark of a shot, if you extracted that long) and then it increases in viscosity, darkens up and comes out with a crema. It maintains a good shot through the rest of the extraction, it's just this first few seconds...
I assume you have fresh beans and are not using the same beans from a few months ago?
The symptom sounds a bit like channeling, i.e. water flows too quickly through a part of the coffee puck. This is often due to uneven tamping or grind distribution in the basket.
Maintain the same coffee dose for now but adjust the grind and ensure that you are tamping level.
I would assume they are fresh beans (it's a commercial business, I changed industries a few months back but I'm helping out today for an event).
Dose is consistent, tamp is level. The temperature and humidity are quite consistent so grind isn't needing much adjustment, slightly finer and it drips, slightly courser and it's starting to gush...
I was wondering if it could be machine related (not that I'm ruling out human error, just that I'm struggling to find things I'm not doing correctly...)
Is it a single group machine or does it have two or three groups? If it's a multi group machine, does the fault manifest the same on each group?
It's unusual for the machine to be the cause of symptoms like these. Perhaps the pump is going over pressure if the internal pressure valve is faulty at the start of the shot but then settling down. The OPV should handle this but it might be faulty or not set correctly.
These problems are out of your control if the machine is currently in operation.
What sort of grinder are you using? Do you know how long ago it was serviced or had new burrs installed?
Sometimes when the burrs are going blunt they will either grind too coarse or extremely fine when you try and adjust it.
Do you have access to another grinder to try? This would at least confirm if it is the grinder or machine at fault.
Twin group, does it on both groups.
Mini mazzer grinder, no idea of last service (as I said, I haven't worked for a few months)
No access to anything else atm either