I noticed my LM double basket screen holes just weren't as clean as I thought they should be. I always wash the screens after a shot, brush them briskly inside and out, rinse them again and dry them off. I soaked them in Joe-Glo once a week. But there were always some holes that did not glitter as brightly as others when held up to the light. I would blow hard into the basket but they just didn't clean out.
After a month with my Silvia I took more drastic steps. I soaked the worst screen in boiling hot Joe-Glo with vigorous scrubbing while soaking (ouch a few times). Repeated twice. Went to the garage, grabbed the high pressure nozzle for the air compressor and point blank blasted each hole in the screen with 100psi. No change -
Out came the WDT tool (a straight dental pick)! From the inside to outside, I tediously poked through every hole in the screen. Each poke I could feel a resistance give way, feel a crack as the hole cleared. When finished, I scrubbed the inside surface with 600 paper until it was smooth.
Here are the results:
The left pic shows how every hole has a cats eye look and some are completely closed off. The right pic is after the WDT treatment, and the right basket was actually worse than the basket on the left. My other unused LM double looks a little worse than the left basket. Conversely, the original 'never used' Rancilio single and double baskets that came with Silvia look just like the right basket.
I've pulled about a half dozen shots so far and the flow is much smoother. The formation of the extraction is more regular and there is much less spurting and multiple cones. The pressure gauge is showing slightly less pressure during the shot, too. In addition, the baskets a very clear after a simple rinse now.
Have you checked your baskets?