In my opinion the importance of tamp is over rated and old hat now. Trying to get a consistent, multi-pound tamp, shot after shot is difficult, frustrating and can lead to discomfort..

Grind finer, dose, knock, level and just rest the tamper on top and polish. The tamp will then be one less variable out of the equation.

The opinion of your business partner also leads me to think the condition of the machine might have something to do with what you are getting out of it. If it needs a clean or descale this can affect the product as well. How did you you adjust the temperature? Are you sure it's not running too hot?

Good luck and keep us posted.

tony359 wrote:Thanks everybody.

The grinder is second hand and I haven't replaced the burrs. Looking at the coffee machine that was supposed to be "serviced" I guess that this could be the trick.

Unfortunately my business partner is a strong believer in "coffee machine should never be cleaned nor touched" and I was unsuccessfully in trying to explain him the very basics, including flushing the groups before the shots - no matter if I was showing him the temperatures with a precise thermocouple. I won't even try to mention him something more complex like burrs or weights, it would be pointless
A precise scale is on its way, I will check the weights later.

Thanks!!!

Sorry to put it this way, but your business partner is an idiot. I would start by getting fresh coffee with a known roasted on date. The second, I would replace the burrs in the grinder. Then I would find a new business partner. If you do not clean, adjust or maintain your equipment properly you might as well purchase pre ground coffee or pods. It will be much easier to make bad coffee, and less expensive. You cannot simply ignore the equipment, it must be properly adjusted and maintained, including daily cleaning. Otherwise you will never get anything drinkable out of the equipment.

Hello cannonfodder,

I do believe that if the coffee machine is left to its destiny the coffee quality will be random, more likely bad.
Anyway, I'm back on the machine and about the tunnelling a nearby bar told me it could depend on the group: if the shower where the water is coming from is not allowing the water to come out freely and evenly, there will be more pression on some areas, with tunnelling.

I have removed the mesh filter that covers the shower and the water pours down like a clogged bathroom shower in fact. Should come out of the shower evenly and not spraying water from 4-5 points?

Well, the machine has never been cleaned since we've got it and I guess that could eventually be the cause . I have tried to remove the shower with a coin, the slot has been damaged by someone in the past but I managed to shape a coin to fit the slot. Unfortunately I cannot remove the shower, the coin bends.

Any suggestions? In fact, it looks like there are some visible deposits and I think that removing the shower for cleaning would be the best option. Is there any special tool required? Is the shower coming off counterclockwise?

Thanks
Tony

ok, I managed to remove the shower of the other group, nothing special it's just a bit tough.

It's clogged with dark rubbish of course, would you have ever expected it?

Update. With new resins in the softener, the water does not smell funny anymore... for the time being. As a result the tea water is already much better (I guess that is coming from the boiler and I haven't emptied it).

The pressure jumped to 12atm - because of the new resins I guess - and I had to adjust the pump. Now I have 9atm and the needle is steady.

Coffee comes out in 10s, I am adjusting the grinder as well.

Despite the cleaned group, I still have tunnelling in the puck.

I have weighted the dose and the grinder is quite accurate I must say: for 7 grams it gives between 7.2 and 7.5 grams.

As foretold (you don't need to be magicians) there is a huge difference.

BTW: coffee tastes good, and it's still not "finalised". More update later on maybe. In the meantime I would like to thank you again for your help.