Evilsports wrote:This is pretty much my take on it as well, only having used it for a day now.

I just looked at the special screens on EPNW - the list price for an EP Sproline screen is $105 (!). The explanation is quite detailed, and I have no idea if it's as important as suggested in the copy - here's the gist of it:

"What makes EP Sproline Precision Group Screens so different? In a word, Cavitation. In the instance of our screen project, we are utilizing the espresso machine pump in combination with the screen to develop Discharge Cavitation. Discharge, or recirculation cavitation, is the result of changing pressure at the point of exit, or outlet. The outlet is not able to let all the liquid through as fast as it should, so the currents' different velocities create miniature changes in the uniform pressure. Even such small variations are enough to create the ideal circumstances for cavitation. Now in the instance of submarines, this is not a great thing, but when used to extract coffee the results are a plus.

The drop in pressure after the group screen allows the ground coffee to absorb water at a faster rate during pre-infusion as well as the extraction cycle. This allows the puck of ground coffee to become more saturated than it would using a typical dispersion screen. The pressure continues to build past the screens point of exit and into the portafilter basket and ground coffee. The resulting coffee is brewed in such a way that the resulting creama [sic] is typically free of large gas bubbles. Coffee that has become dated and stale can seem revived under this process, allowing for more working days with some coffees."

Wow!

I'm not sure that makes complete sense re: the physics, but it's certainly a beautiful screen to look at (I try to find pleasure wherever I can.........)

I have used the IMS screen for nearly a year. It makes no difference in the cup whatsoever, when compared to a new, clean, high-quality screen. Its advantage comes from the fact that it is easier to keep clean, and it requires less cleaning, as it does not get clogged on the backside with particulate coffee nearly as much with normal screens.

The Sproline screen actually seems to make extractions worse. much of the time, in my experience. I tried it some time ago, and actually gave it away. It allows lots of coffee to enter the backside of the screen, though it is easy to clean. If deformed at all by overtightening the group screw, it works very badly, causing very uneven extractions. It should not be used with finely ground coffee.

Interestingly, I think that the Sproline group screw may be useful. It splits the water stream 5 ways instead of 4. The water coming out of any screen below this screw is visually a bit more even, and looks good. I have used this with both the Synesso and the Slayer. It makes no difference in the cup whatsoever that I can discern, but it looks cool.

All of this is just one person's anecdotal data, but barring major flow problems from obstruction and flavor corruption from dirty screens, I really don't believe that screens make a difference in the cup. I use the IMS screen because it requires less maintenance to be and taste clean, and it requires less frequent replacement.

- Mike