The dispersion screen on my Olympia Cremina 67 keeps popping off. I've tried to re-crimp the sides and pop it back on, but after a couple of espresso pulls it pops off again; scared me half to death first time...I thought I had blown a seal or something! Is there some trick to doing this right? Do I just need to crimp it more to create more friction to hold it in place? Since they are not cheap I'd rather avoid this, but would I be better off ordering a new one? Actually, I just checked the OE web site and I don't see the screen for sale anymore...so I hope there is a remedy for mine!

TIA,
matthew

There are a couple of things to check. First, examine the outer cylinder at the bottom to see if the groove on the outside of the cylinder is clear. This groove is where the screen is to seat and if it is full of coffee gunk it could interfere with the proper screen installation. Next, check the surface of the screen...is it curved or is it flat? If it is curved upward, cupped, then you may be able to flatted it back into shape with a flat tool and a hammer against a flat surface. You may have to try to get it slightly curved outward...this will move the rim insard and make the edge a bit smaller. And yes, careful bending of the edge inward is another option. Our source material for manufacturing these screens is on back order but we shall have more when we get the right stuff to make them....unfortuneate unobtainium part from Olympia, which makes absolutely no sense, if you ax me.

If there is a lot of gunk on the bottom of your piston, it will pop the screen. Cleaning the end of the piston worked for me. Plenty of Cremina threads on how to do that.
~Richard

Doug and Richard,
Thank you for the responses. The last time it popped off I cleaned around the edge of the cylinder with a Q-tip to make sure all the gunk was off. The first time it popped off, I cleaned the whole screen in cafex to get it nice and clean. Last night I removed the screen to re-crimp the edges of the screen with a needle nose plier (carefully bending each of the segments in a little bit so as to give more grip). I also made sure that my piston was not dropping beneath the surface of the cylinder (and thus pushing the screen off directly). However, assuming it pops off again this AM, I will check for convex/concave and make the correction you suggested Doug.

I also had another theory: I recently switched over to the RP naked portafilter (which I LOVE) and the new (elektra?) basket which is deeper. When I did that, I increased the amount of coffee I dose. I wonder if the puck is swelling up now, making contact with the screen, and then slightly pulling at the screen when I remove the PF (thus causing it to eventually pull off the cylinder). To test this theory, I might either: decrease the dose (and increase the fineness of my grind) or temporarily go back to my old PF/basket (with smaller dose) and see if that resolves the problem. I figure once I have it diagnosed that I can then go back to the naked PF (which is teaching me a lot more about my technique).

Guys, thanks again for the responses!

TIA,
matthew

Hi Matthew,
Your idea is certainly worth the trial. I have not noticed any difference between the Oly and Elektra baskets as to popping the screen. My screen , not original, rattles a little. If you have an original screen, they may want a slight convex down to assure that the screen stays in place. I had my problems with about a .7mm gook build up on the bottom of the piston which was just enough to unseat the screen. The Elektra basket should take an honest 15-17gr of coffee if it is ground properly I like ristrettos and so really overdose.. More than that may spring the center of the screen upward.
Good luck!
~Richard

The screen popped off again this AM after my second pull so I took the opportunity to inspect the piston and the lip where the screen contacts the piston wall; both were pretty clean, though I wiped them off again. To try and get a little more convex bend in my screen I centered it on the handle of my tamper and then pressed down on the edges of the screen. I then replaced the screen and pulled two shots without it popping off.

I also reduced the amount of coffee I'm dosing. I had been at 16.8 grams, but cut back to 15 (making the grind a little finer to compensate for the reduced dose).

Fingers crossed that it continues to hold through tomorrow AM's espresso ritual If it does pop off again, I'll try to bend the screen a bit more...I guess the good thing is that I can usually get through my morning espresso requirements before the screen pops off.

Another thought...maybe your piston is adjusted too far down? You can set it a bit higher by changing the rod nut setting (it is supposed to be 1/2 turn back from tight then the cap nut tightened against the jam nut). The piston could be hitting the screen and you could raise it until it does not hit any more by doing this nut adjustment. Also, your piston could be unscrewing from the rod, which could cause this to happen, and other weird things as well.

The piston looked like it was set correctly to me when it popped off the next morning...so I got a little more aggressive with the crimping on the edge of the screen. I used a wooden mallet and with moderate forced tapped all around the edges several times to bend them in...and so far it is holding. If it continues to hold, it would seem that after 27 years of use the edges had been pried out just a little too much to create the friction required to hold the screen in place.

Cremina dispersion screen falling off... solved.

Hope this helps.