Scotto wrote:It would be interesting to separate out the two variables - dosing weight versus space between top of puck and shower screen.

I've tried to do a little of this.

My impression so far is that the taste effect of dosing changes is rather smooth and fairly subtle when dealing with changes of 2 grams or so. The lower dose will be slightly softer and sweeter; and you pick a spot where the shot is neither too flabby nor too aggressive.

My impression of head space is that in certain machines the effect is completely drastic. If the puck has just enough room to expand, the shot will be good; if you then go just 1 gram further, everything goes to hell in a dramatic way. I think this is due to some as yet unknown in the nuts and bolts of the group design. The Elektra is the most dramatic "Max Headroom" machine; hit the shower screen and the shot loses 10 points instantly. The Silvia also shows a dramatic change, as do the La Cimbalis. The E61s and LMs, on the other hand show almost no change at all, and these machines can be overdosed with near impunity when using milder tasting blends.

It is again worth noting that the performance of the group with an overdosed and compressed puck is not something to which the machine designers paid attention. These machines are all designed for doses with adequate head space. The better performance when overdosed of the LMs and E61s is an accident. Ken's been trying to drive this very simple fact home; and I think most of the thread's readers are getting it.

another_jim wrote:It is again worth noting that the performance of the group with an overdosed and compressed puck is not something to which the machine designers paid attention.

I am not sure if this is entirely true; I would guess that the testing of at least the Synesso involved some fairly large doses. This is merely conjecture on my part though.

Scotto wrote:It would be interesting to separate out the two variables - dosing weight versus space between top of puck and shower screen.

One must also take into account the profiles of the shower screen and tamper when aproaching zero clearance.

The original Vibiemme screen is quite rounded with a recess at the edge of the puck. Overdosed shots and a tamper with a radical profile are likely to spritz on the Vibiemme, with the attendant taste defects.

When the original screen is replaced with a flatter one with no edge recess and a closely matching tamper profile, one can updose with impunity up to the point the machine chokes, ~17g in a 12g basket. Doses below <14.5g are similar to bars in Italy, while the higher doses are more similar to shops in the colonies.

With doses below 13g, the tamper profile is irrelevant.

I've been examining my dosing and tamping technique pretty closely since I got a bottomless portafilter for my Anita. I just started examining how to achieve the correct clearance with the top of the puck to the shower screen. When I dose/tamp to just below the ring on the standard double basket (that came with the Anita) and lock in/remove the portafilter, I find grounds on the center (but not the outside edge) of the shower screen. The resulting pours taste pretty good, but I am struggling with edge channeling.

I am already significantly shaving ground below the top of the basket before I tamp. Should I try to shave more off or are there other techniques I should try?

How is the shower screen removed on my Anita?

avdiscolo wrote:When I dose/tamp to just below the ring on the standard double basket...

Ridgeless baskets are more friendly.

avdiscolo wrote:How is the shower screen removed on my Anita?

The wrong way.
Place the screwdriver in the notch for the ears and use the corner of the blade to 'snag' the side of the basket ABOVE the ring that holds the mesh. It helps if you've backflushed a couple of times and done a portafilter wiggle to lubricate the gasket.

HB wrote:As Jeremy and I noted, it's "wrong" if your machine has the dispersion screen on the left, otherwise it makes no difference.

I've seen a few machines where the screen was so 'welded' to the group with gunk that regardless of the screen type, the method in the photo would result in a destroyed screen. Better safe than sorry.

As Jeremy and I noted, it's "wrong" if your machine has the dispersion screen on the left, otherwise it makes no difference.

Dan- What is the make of the "right" screen, and where did you order it.

Thanks

Matt