Getting thoroughly uneven extractions w/Olympia Cremina - Page 2

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Eastsideloco
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#11: Post by Eastsideloco »

Based on how long you've had your Cremina, you're probably overdue to pop off the shower screen and give it a good soak in coffee cleaner. That's the only way to know for sure that the screen isn't blocked.

Generally speaking, the shower screen on a lever machine will stay relatively clean, certainly as compared to a machine with a 3-way valve. But if you use a shot preparation routine that incorporates more than one movement of the lever, you are at increased risk of pulling goo up into the piston and shower screen. These additional movements of the lever also increase your risk of cracking the puck, which will lead to uneven water flow out of the basket.

If you think about the fluid dynamic inside the piston, the machine itself doesn't need to be hyper level. (If the machine is grossly out of level, you should be able to see that. Are the four pads identical? If so, it is level enough.) What matters is whether the face of the piston is parallel in relation to the dispersion screen. That's what defines your water column, which you then press through the puck. That should all be kept parallel based on the construction of the machine.

So I'd start fresh by giving the shower screen a thorough cleaning. Once that is complete, I'd simplify everything about your routine so that you can evaluate the water flow out of the group/basket in isolation from other factors. Once you know that the dispersion screen is clean, the most likely causes for uneven water flow through the puck are always distribution and tamping inconsistencies.

/naked-extr ... blems.html

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CrabRangoon (original poster)
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#12: Post by CrabRangoon (original poster) »

David, removing & cleaning the shower screen was next on my list of things to do for this issue. When I flush the group after a shot, there's hardly any traces of fines or particles when using the HG1 or Pharos, but some evidence of them when shots are ground with the Lido. I recently stopped doing the small pumps during/after preinfusion in order to build pressure & purge air, now most shots are 28-30g as opposed to 32-37g and pucks are smoother on top.
rpavlis wrote:Here, for what it is worth, is my Hg-one grind technique, regardless of machine:

1. Weigh coffee beans
2. Place beans in ramekin, add 3 or 4 drops of distilled water. Stir. (I do not want the salts in our horrible water in my grinder!)
3. Dump coffee into grinder.
4. Grind into blind tumbler. (Remove "funnel" to check no coffee is clinging, tap if necessary.)
5. Place filter basket on rubber pad. Place blind tumbler on top. Stir with centre in place. I tend to use a chop stick.
6. Remove blind tumbler centre piece. Stir again. Shake a bit to level.
7. Remove blind tumbler. Tap a bit to level.
8. Press.
It's good to know I was doing all the right things when borrowing David's HG1. With my (recently acquired) Pharos, I'm doing mostly the same, as I did with my Lido before that. Weigh beans; spritz them w/martini mister; grind; dump grounds out onto parchment paper; pour grounds into basket w/shaking & settling between first and second half of the dose; "slap shot" to settle grounds before doing a light leveling tamp. Today I put the grinds in a glass & gave them a good stir before finally adding them to the filter. Had good shots doing that, but still a small bald spot near the center :x
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drgary
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#13: Post by drgary »

It looks like you're well on the way. Making the center concave may solve the "bald spot."
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

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CrabRangoon (original poster)
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#14: Post by CrabRangoon (original poster) »

Still have yet to change from flat to curved tamper face, but (in cup) shots look and taste fine. However, I can confirm that my group does not sit level as it definitely slopes down toward the front. Not sure that there's anything I can really do about it (correct me if I'm wrong), because when I replaced the boiler-to-group gasket with the updated 2011+ teflon piece I confirmed that all 4 allen bolts are properly tightened and the group is as unlevel now as it was before.

I was gifted a new set of taller glasses and found that when using them they make contact with the Penney portafilter at the front-facing point, but have an increasing gap toward the rear. I figure the only possible fix is to try some thin DIY shim placed at the bottom of the group, between the lower 2 allen bolts, but worried that it may not fix anything and would alter the seal of my teflon gasket. Any ideas?

Again, I'm sure this won't have any real effect on my shots, but when using a double spouted PF only one spout gets any flow, and on the Penney I get a wandering concentrated flow as the shot progresses.
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Eastsideloco
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#15: Post by Eastsideloco »

As I recall, your machine looked like it had experienced some shipping damage en route to Austin. If so, I'd take the case apart and make sure that the frame and other parts aren't tweaked and out of alignment. The group on a Cremina should be perfectly parallel to the drip tray.

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