i have recently acquired a QuickMill Vetrano and am experimenting with my tamping and dosing.

Based on input here at HB, i'm trying to dose enough coffee and tamp such that I leave the top of the ridge for the basket retention clip exposed. as a test, after i lock in the pf, i unlock the pf to see if the puck comes in contact with the screen before the pour. there is usually some contact and some grounds have stuck to the screen. does that matter? should i be aiming to dose & tamp such that the grounds do not come in contact with the screen at all before brewing? i've also read here that avoiding contact between the puck & screen is a goal. i'm not getting any resistance when locking the pf. but there is clearly some contact.

thoughts?

Bob K.

You probably want a bit of room between the screen and the top of the puck.

A simple way to check for this is to place a penny lightly on the top of your (already tamped) puck. Lock the PF into your machine and then take it out again. Gently lift the penny of the top of the puck. If you can see an impression of the penny in the top of the puck your dose is a bit high.

bpkengor wrote:there is usually some contact and some grounds have stuck to the screen. does that matter?

Depends on who you ask ...

Depends on what coffee and basket you are using ...

When you hit the screen while locking it in, and this depends how much of an overdose there is, it can mess with the integrity of the prepared coffee cake and provoke channeling. Using a convex tamper can help tremendously with allowing you to dose on the high end and stay off of the screen. The screens on the QM groups are somewhat convex themselves.

I'm glad you posted this topic. I was thinking of asking exactly the same question because this has been bugging me too!

I've read a lot of differing opinions on this and I still can't decide for myself whether or not it matters after playing with my Mininova for the last few weeks.
My screen is ever so slightly convex downward, but my tamper is flat. Of the times I've removed the PF to check if there was contact, there usually was, but only in the center. I only started doing this a week into playing with the machine after getting it fixed. With some coffees I began dosing upwards of 18g and it completely went over the ridge in the basket (apparently a no-no according to some). I'm sure that the shower screen wasn't only touching the puck but it was probably pressing it down with considerable force. I didn't feel much if any resistance trying to lock in though. Interestingly enough, however, when I started paying more attention to head space and dosing less my shots became progressively worse! I started noticing less crema and harsher flavors coming through more than when I updosed. I was getting symptoms as if the temperature were too high but I didn't change my flush times or pstat or anything. If I dose so that there is room between the puck (a mm or two under the ridge) I end up with a pretty wet puck (but not soup) and a not-so-good espresso, just about every time. So either I'm doing everything wrong according to conventional wisdom or I'm really on to something here. Or my machine is a fluke. It doesn't help that I just ran out of the blend I've been messing with so I'll have to start a new log all over again. I also don't have a way to accurately measure temp (yet) - I've been going by the sound of the water from the flush and counting the seconds that pass by. Not the best method of course but it's all I've got at the moment.

So basically, most of what I've read about E61 technique has said yes, leave some room between the puck and the screen or your extraction will be uneven. Strangely I've not found this to be the case, but I can't confirm anything without more testing (and more caffeine! ).

I'd like to hear what others have experienced. It would help to be specific about your particular basket (ridged/ridgeless), screen, tamper, etc.

I'm finding the same as you are oofnik. If I dose down far enough to completely miss the screen (much less put a penny or nickel in there) bad things start to happen. I've noticed the best shots come with the puck just under the retention clip ring and slightly impacting the dispersion screen (before extraction).

As a note of interest my Andreja instructions read "Inside your portafilter metal basket, there is a ridge about 1/4" down from the top. ...compress (tamp) the grounds to approximately the hieght of the ridge". When I do that I get a good shot; when I do that the dry puck always touches the dispersion screen.

I've had a Quickmill Anita for about five months now, and I feel like I'm starting to get a grasp on the appropriate dose for her. I started with a flat tamper, but going to a convex has helped with avoiding contact between the puck and the screen. I've also realized that, at least for the stock basket, I need to just level the grounds with no pressure. Of course, this will vary depending on the coffee you are using and whether you have a QM machine or something else.

I also purchased a couple of LM ridgeless baskets. They allow me to dose a little higher while still avoiding contact. For me, I'm getting better looking and tasting extractions when I don't overdose to the point of making contact. I also find this is especially important if you're using a coffee that has any dry-processed beans. For those, I need to underdose. I think you all probably realize that the grinder will need to be adjusted as well if you are changing your dose.

One mistake I've made is changing too many variables at a time. If you are trying to figure out your dose, make sure you are keeping the rest of your technique consistent. Don't tamp poorly or pull the shot too hot because you're worried about the dose. Also, there's a school of thought that a finer grind and a lower dose makes for a better cup of coffee (with a slightly lower volume), so don't accept that you have to dose over 18g in a stock basket or whatever you've read. Try different things. You might like it!

Oh, one more thing to check regarding puck to screen clearance. If you examine the puck after you pull a shot, before you knock it out, you will probably see an impression of the shower screen in the coffee grounds. You can tell by how firm the impression is whether you're leaving enough space. It should only be a slight impression, and not too firm. If you have no impression at all, you might want to try a higher dose.

Justin