yellow / orange gunk in the group screens

[BrewHaHa]

Often when cleaning the group screens, I find them clogged with yellow/orange gunk. This "gunk" is a really resilient, rubbery substance that blocks the holes on both of the screens.

It's not so obvious until you hold one of the screens up to a flat light source, such as a florescent light, but then it's like "Whoa! didn't I just clean that???"

Until I realized what was going on, I'd just been cleaning the screens by soaking in Cafiza for a half an hour, as directed, then scrubbing with a toothbrush and rinsing. But then one day I held the screens up to a light, and realized that many holes were clogged even after my "cleaning".

Only a long soak in alcohol seems to dissolve that gunk. And this is after using a (freshly cleaned) screen in the Vivaldi for only a week or so, pulling a few shots a day.

I just thought I'd just mention this to folks who, even though you may clean on a regular (or, uh, less-than-regular) basis, don't look at your screens very closely. You might find that you have more clogging than you think. (And it seems to me that such clogging can't be good for extraction.)

[Endo]

I'd be more worried about my health than the extraction.

Let us know if you find the origin of the gooo. Could it be starting upstream of the machine?

[BrewHaHa]

I'd be more worried about my health than the extraction.

Let us know if you find the origin of the gooo. Could it be starting upstream of the machine?

I have the typical CC softener and filter upstream, and we have very good water here in PDX, so it doesn't SEEM to me that it's a water quality problem. (But, of course, I don't know.) I figured it's some kind of coffee buildup.

After each session I flush the group while brushing to remove any grounds sticking to the screen. I mostly use Stumptown Hairbender coffee, or occasionally some other locally roasted coffee. (I.e., nothing "weird".)

I don't want to overstate the issue, BTW. By no means are the screens covered in gunk or anything. Even before cleaning, the orange stuff is not readily apparent. And although some holes remain clogged after cleaning, the substance is translucent, so you have to hold the screen up to a light very carefully to detect it. For me it's difficult to see the clogs by holding the screen up to an incandescent bulb; a flatter light source works best. (Like some kind of light shade or diffuser - in my case a florescent light.)

Rethinking things, maybe I'll swap screens and go for a week without brushing the screen after sessions - just flush and wipe with a paper towel or something. Just MAYBE the brush is either the source of the substance, or is grinding in the coffee in some way.

[JohnB]

I never saw anything like that in the two years I owned my S1V2 & I checked the screens closely after cleaning. How often do you swap out the screens? What do you think the yellow/orange gunk that Cafiza doesn't dissolve is? Does it clog the holes in the dispersion block?

[chas]

Strange. Maybe you'll get famous for discovering a new life form!

[Endo]

Orange makes me think "rust". Although there is not much to rust in the S1, could it be rust in one of your upstream pipes, components or fittings?

[JohnB]

Cafiza would remove any rust stains on the stainless screens. If a mild solvent(alcohol) is required its got to be oil based gunk. Maybe you were overdue for a detergent cleaning? Using really oily beans?

[BrewHaHa]

How often do you swap out the screens? What do you think the yellow/orange gunk that Cafiza doesn't dissolve is? Does it clog the holes in the dispersion block?

I typically change out screens every week to 10 days - sometimes 2 weeks. When I'm not lazy or distracted, I swap screens after a week, then on the second week clean both sets of screens and the dispersion block, and do a Cafiza backflush (specifically, dose the blind portafilter with Cafiza and do 5 backflushes, followed by five more plain water backflushes to clean things out.)

Does it clog the holes in the dispersion block?

It definitely doesn't even come close to clogging the dispersion block holes. It would be difficult to determine if it built up in the holes at all, but I'll see if I can see any signs of it the next time I do a cleaning.

Cafiza would remove any rust stains on the stainless screens. If a mild solvent(alcohol) is required its got to be oil based gunk. Maybe you were overdue for a detergent cleaning? Using really oily beans?

Yeah, it doesn't seem like it would be rust. In a stretch, maybe it's colored by rust. But the "gunk" substance itself is somewhat rubbery - not at all like a metal/mineral deposit.

The gunk appearance isn't a one-time deal; I first noticed it months ago, and it's an issue every time I clean the screens. It was definitely worse back when I first noticed it. Back then I cleaned screens and backflushed closer to once a month.

The beans I use are not oily looking. Their outside appearance is quite medium brown and dry.

I did an experiment this afternoon. I dropped and inspected the screens that had been in use for 3 days. They showed no signs of clogging - yet. I put them back, and ran a bunch of plain water shots (i.e. flushes) to simulate the amount of water that goes through in 10 days. (100 2 oz flushes.) After that, the screens still showed no signs of the gunk. I realize this wasn't a very scientific experiment, though. Flushing through water through over such a short time doesn't allow for the possibility of something being dissolved into the water line, or for water evaporating on the screens and leaving a deposit, for example. But again, there is a water softener cartridge and a filter cartridge (from Chris Coffee) directly in line before the Vivaldi, so I don't think there's anything bizarre in the water. (Plus, we love our great tasting, soft Portland water; we don't filter it for use as everyday drinking water.)

BTW, I speculated earlier that maybe the screen cleaning brush had some effect on this issue. I guess that can't really be the case, since the gunk shows up on BOTH screens, not just the exposed one that I am scrubbing.

I guess it must be coffee residue. As JohnB speculates, it's probably the oils from the coffee. Maybe I'll try running a different coffee through the machine for an entire 2 week period to see if I see any difference. (Dang - just bought a bag of Hairbender!)

Well, thanks for your input.

-John

[JohnB]

I swapped out screens every 3-4 days so that could be one reason I never saw this. Even then there was a collection of old grounds trapped between the two. Maybe the trapped grounds break down into what you are seeing after 10 days??