tracerbullet Senior Member Joined: 13 Feb 2012 Posts: 152 Location: Saint Paul Expertise: I love coffee
Posted Fri Dec 14, 2012, 2:45pm Subject: Re: Problem with Gaggia Classic post cleaning.
Glad you got it solved.
THe materials, as I remember them: Boiler (upper half of main piece inside) is aluminum , group head (lower part of main piece) is brass with chrome plating, dispersion block is aluminum, and the shower screen is stainless. Also, there's a copper tube in the group head itself sticking up into the boiler. Quite the combination of material.
Interesting idea to replace that lower aluminum dispersion block piece with brass!
If I remember the flow path correctly, water comes in through a fitting attached to the group head (either just a fitting or an OPV, depending on the model). There's a hole through the lower part of the group head on that side connecting directly to the inside of the boiler itself. It fills up the boiler area, and then spills over the copper tube in the center of it. That leads down to the 3-way solenoid which is also connected to the group head. From there the water turns right back around and into another hole close by back into the group head, leading down towards the dispersion block and shower screen. The 3-way solenoid alternates between connecting the dispersion block / shower screen area to the boiler when it is energized, or that area (db / ss) out the top of the solenoid when it's not energized (the top of the solenoid has a tube connected to the area underneath where you place your cup). I could be wrong of course, I haven't had one apart in a while!
Also - the 4 bolts mentioned earlier just hold the group head to the chassis of the machine, as long as they aren't overtightened you're fine.
I only ever backflush with water, every couple of days or so. Having taken a bunch of these things apart and not even getting some items clean after soaking overnight in some heavy duty industrial stuff, I'm skeptical of how momentary contact at light mixtures of cleaning products actually does anything. Now, that doesn't mean that it doesn't do anything, but I've convinced myself not to worry about it. The solenoid itself has some rubber in it, which I am concerned about damaging (I can see where a bit of debris can keep it from fully closing).
I don't think there is a problem using Cafiza with aluminum. Just watch out for acids used in descaling with aluminum. Also, you can use the cafiza as 'liquid' if you just dissolve it first in hot water. I have found the Cafiza to be an excellent cleaner for coffee residue. (many other things as well) I have a small collection of old stove top espresso makers I picked up used here & there. It is amazing the filth that cafiza can remove with just soaking. Some of these have aluminum parts that have not been harmed with Cafiza.
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