BartG wrote:I would leave the standard strega shower screen as is, nothing wrong with it.
Your new tamper will fit much better (I even went for a 58.5mm model for the HQ baskets I use with my strega). But I doubt the tamper will do much to improve channeling and proper pour. A good WDT technique and uniform, level tamping is probably the most important for that (together with a good grinder, but you have an HG1, no problem there )

The standard screen has a lot of dents after a lot of cleaning.
I am not totally sure about the new tamper, so we will see. Though, as I said, I think that I have done everything to improve the pour.

I received the new basket, shower screen and TORR tamper just a few days ago. With those I got a nice centered flow using a double basket for the first time.
I do not have enough data to make a statement, as I tried different combinations only ones, but I think not only the 57mm tamper were the cause of the uneven flow, but the bezzera basket has poor quality. I need to find a caliper to support this.

SuchBrewSoCoffee wrote:... the bezzera basket has poor quality

I would doubt about that: my Strega, bought one year ago, had a 16g basket for doubles and I bought an extra one for working on head-to-head shots; they worked fine for me - I'm using several tampers between 58,12 - 58,45, depending on the dose;
still I wanted to see what's about IMS baskets performance, so I bought 2 pieces of IMS - B70 2T H26.5 M;
well, they are gemetrically identical with bezzera's 16g! only the IMS looks better polished;
same height 26,5mm same 641 holes, in exactly the same pattern, same volume (volume dosing gives cca. 20,5g) etc.
I've never checked with a macro lens or a microscope, the internal shape of the hole, if there is kind of a conical shape difference, but anyway, I can't tell the difference in results!

also I have several other bezzera baskets, like de 12g, 14g and the 'triple cup' one; the latter one looks quite well, apparently the same geometry like the 21g VST (not checked), is 28mm high, has 58,84mm internal diameter at mid height (actually the walls are cylindrical), has 715 holes, and is made by Nuova Ricambi (possibly like all the others);

radudanutco wrote:I would doubt about that

Finally I measured the stock basket with a caliper thrice, my main concern was it had seemed to me that the whole hole design is slightly misaligned. The caliper showed 3mm distance from the each utmost hole to the nearest basket wall, and, although my measurement was not done very precisely as the basket is rounded, my worries went away. Thus I think it is connected with a small tamper.
Though I recently noticed another thing - first drops under the basket show near the handle. Every time I observe that the strongest water jet flows in exactly that direction while I am flushing. I am not sure if this affects anything.

By the way, you said you are using B70 2T H26.5 M which is for 16/20g, and I have B70 2TC H24 E (12/18). Mine 17g puck fits there, but it touches the shower screen. Perhaps I should have chosen the bigger one.

SuchBrewSoCoffee wrote:... first drops under the basket show near the handle. Every time I observe that the strongest water jet flows in exactly that direction while I am flushing. ...
By the way, you said you are using B70 2T H26.5 M which is for 16/20g, and I have B70 2TC H24 E (12/18). Mine 17g puck fits there, but it touches the shower screen. Perhaps I should have chosen the bigger one.

you say about a new shower-screen... however, you should test it with with a cleaned stock shower screen, as well as with the stock basket, if this is a bezzera 16g, p/n 5471035; I mean, with this setting I have no problems in water flow at flush:
https://youtu.be/Y_yt9BjoAB8
(at sec 15 is the pump flow - about 10-10,5 ml/sec, and at sec 21 is the piston and springs pushing the rest of the water and air/steam)
it is true that the water inlet hole is at the opposite of the handle zone, inside the cylinder,

but the chamber is quite large, and first part of the flush (2-4 secs) is flash-boil, so the whole chamber is filled with steam and water, and the steam is condensing on the cooler walls...

I leave the portafilter in group after the shot (while preparing the other basket), and when I took it out, the puck is fine, dried enough to fall as a brick in dropbox, but still, I can see often, a kind of moisture spot, on the upper left part of the basket/puck; I am supposing it has to do with a gasket problem; but this is not your case with an uneven flow during flush;

and yes, if a basket is overdosed - in my case, those 16g bezzera, or IMS with 26.5mm height, if I put 21g in it - I can see the center shower mark on the puck;
as I said, I have several smaller baskets, but I prefer to use larger doses for doubles: 19-20g in for 40g out;

The flow is fine. It is just that I started to tamp lightly, so it seems that initial flash-boil penetrates the pluck instantly in one spot.
My doze is 17g for both stock double and IMS basket.
Actually I am trying to extract with the lower pressure and light tamping.
I added a photo to show what I was talking about.

It appears the tamper is way too small for that basket. Could try a calibrated VST basket (size your choice) + pergtamp or equivalent 58.5+ reverse canted tamp. would be one less thing to worry about, no?

I started with a VST and a standard 58mm tamp. Moved to 58.4mm, to me both caused occasional side channeling. Now my 58.55mm Pergtamp actually started to cause a suction problem (fixed with an ultralight spin). This change took care of edge channeling for me.

Edited my first post; I was angry about working too much that day;/. I wish you well

I already bought TORR 58.40 convex tamper and an IMS basket and a shower, and I think I'm rather happy about it. That nasty photo from the previous post shows a result of what happens if one tamps too lightly - the initial water stream simply penetrates a few holes in the puck.
Another issue I had, which I realized not a long ago, is that I tamped right in the basket without a portafilter or any stand. Because both the stock double basket and the ISM basket have a rounded bottom, you can imagine what was wrong. As for now, I tamp in the portafilter.

SuchBrewSoCoffee wrote:... it seems that initial flash-boil penetrates the pluck instantly in one spot.
<image>

you could say that if the puck became saturated (coffee drops on the bottom of the basket) before pressure starts to ramp, that is, in the first 5 secs of 0 bar soft preinfusion;
I mean, the flash boil water enters the chamber in first 3-4 secs after the inlet hole is opened (lever descend under horizontal position);

in fact, I think the overheated water at 100-105C (depending on the recovery time before) enters the large volume of the chamber (pumped at 10 ml/sec) and almost instantly the vapors are expanding and condensing on the much cooler walls of the cylinder (somewhere at 80-85C), and after the initial 20-30 ml of superheated water, follows the lower temperature water (HX water mixed with the cold one injected);
what I am trying to say, is that the puck, during first 4-5 secs of chamber filling, never has the chance to support some significant pressure from some flash boil water above; just kind of a soft soaking;
in fact, as I did today too, I am continuing the first 5 sec of pump running at 0 bar in chamber, by stopping the pump and letting the puck to 'rest' under the hot water inside for another 5 secs;
no signs of puck saturation in this interval (coffee drops);
then I am continuing with a full pump pressure ramp until I see the puck saturation (about 7-8 bar), then stop the pump until the pressure drops to 4 bar, and only now, I rise the lever to apply the spring pressure, sometimes with a slight lever retention for diminishing the maximum pressure applied (the idea of a lower pressure brew; in this case, two pressure 'humps' and 2 pressure slopes)
in my case: no flush at all, 20g rather fine grind - WDT only with basket, normal tamp in PF, 48-50g in the cup (until lever stops), yet the liquid has color; blended coffee medium roasted (by me), medium-standard quality;