Pay attention to dispersion block hole alignment

[DavidMLewis]

Some time ago, there was a thread in which someone asked about holes in the top of the puck. I'd occasionally seen that, so the next time I cleaned my machine I checked. My Techno is like many other machines in that there is a brass dispersion block with six holes in it. Above that is a small plenum with one hole feeding it. Below the block is the screen assembly, which consists of a stainless disk with holes punched in it attached to the stainless screen itself.

By putting the block over a flashlight, it's possible to orient the screen assembly so that none of the holes in the screen assembly align with the ones in the dispersion block. It's also possible, with a little care, to put the block and screen back so that the feed hole in the head itself lies between two of the six holes in the dispersion block.

Doing this takes less time to do than it does to read about, and pretty much eliminates having the water drill holes in the top of the puck.

David "is this the OCD support group?" Lewis

[HB]

It may be a little OCD, but Jim proffered a related explanation for the Elektra's high forgiveness factor ("The water goes through two dispersion blocks and a shower screen which are elaborately engineered to provide straight down, ultra-even water distribution over the entire puck" in Why is the Elektra Semiautomatica So Good?).

[cannonfodder]

Until the holes in the dispersion block start to plug. Then the even streams turn into jets and bore holes in the puck. I know it is time to clean it when the water from the shower screen starts to flow uneven and spray the front of the machine. It has to be removed and cleaned about every two months.

[another_jim]

There's gold in the dispersion-block hills, but I'm not quite sure where.

One really obvious thing is that there's a lot more coffee at the circumference of the puck than in the center. So a dispersion block that has a ring of small holes around the edge is likely to do a better job of quickly and evenly soaking the puck than one that has a large hole in the middle.

Getting a fast even soak is necessary for a machine without a preinfusion mechanism. Even increasing the dwell time by adding a tighter gicleur is not going to help: there'll be more time to soak the puck, but less water, since the gicleur strangles the flow; so the puck will get a drip, drip, drip in the center and still soak unevenly, with a soggy center and a dry rim. A real preinfusion mechanism that pumps in a lot of water at low pressure makes the dispersion block far less important, since there's lots of both water and time to finish soaking the puck.

So, for most machines, it's probably better to have a dispersion block with lots of little holes that need aligning and cleaning than one that has a few large maintenance free holes.