Schwarze Oxidschicht statt Kalk im Kessel

hmmm...

the black coating could probably be a lot of different things, - even iron from the waterpipes in house (as a result of a weak electrolytic process, caused by e.g. the current through the water-level sensor).

But I think the relevant question would be: does this coating add an undesired flavour to the coffee?

I do not spend much citric acid (zitronensäure) on it, for several reasons:

1. I really can't taste it (but that may be due to me having poor taste).
2. when scratching the "black surface" it seems to be very hard, and hard things seldom resolve easily in water, so I guess I don't get much of it in my coffee

In fact, if I open some used machine for restauration and only find the black coating, I see it as a sign that the machine probably has been well-maintained and running on well-filtered water (no kettelstone) - a personal theory that I wouldn't mind some comments on.

I only clean the HX and the heating element to the bare copper. The HX is cleaned, because I just like it to absolutely clean, and the heating element, because this is important for the efficacy of this part.

But I don't spend much citric acid on the boiler itself, unless there is a serious build-up of kettelstone. First of all, the water in the boiler is not used for coffee in a two-circuit system, and secondly, I do not want to risk weakening parts of the boiler by etching the copper. Maybe I am being overcautious ? I do know that the citric acid will resolve the kettelstone much faster than the copper, but all the same... ;-)

Anyhow, - all this is just my personal oppinions, not scientifically based facts, so I would welcome any comments.

(by the way: which flavour do you prefer to add to your coffee: pure copper, or copperoxide?)

 

Hallo und guten Tag,
also Kupfer(II)Oxid. Habe beim wechsel des Sicherheitsventils auch so eine schwarze Schicht entdeckt. Habe ich ignoriert. Aber wie kommt das in meinen Maschine :?:

 

nun..sauerstoff is im wasser enthalten...und kupfer ist wohl im kessel...

 

Was für Salzsäure nimmst du und wie stark verdünnst du die Kaffeemaschine 24 ?
Gunnar

 

Bin grad am Zerlegen meiner Rancilio S27, mein Kessel ist innen auch rabenschwarz. Nur ist mein Schwiegervater Industriemeister Metall und der sagte mir, da kann ich hinschrubben soviel ich will, das Zeug krieg ich auch weg, aber das kommt auf jeden Fall wieder... also bringts das garnicht. Wie bereits oben im Thread erwähnt ist das eine Oxid Schicht, weil das Wasser mit dem Kupfer reagiert. Und das immer und auf jeden Fall! Ich werd seinen Wortlaut hier nochmal exakt posten, wenn er wieder aus dem Urlaub zurück ist!

Grüße, Thomas

 

Salzsäure

Just a quick note on "Salzsäure" (hydrochloric acid): this acid should be used with great care in an espresso-machine!

Acids have different "taste" in what they "eat". Citric acid (Citronensäure) will "eat" a lot more kettelstone (calcium, etc.) than metal, but is slower at doing so. "Salzsäure" will eat the kettelstone much faster, but will also eat away on the copper parts, so unless you make sure that the acid does not get in direct contact with copper parts, you should not use it.

As an example: the boiler (kettle) may be heavily coated with kettlestone in the lower 2/3, but almost free of the debris in the upper 1/3, - if this is the case, make sure that you do not fill the boiler too much, - a "less-than-perfect" joint for some piping may suddenly start leaking!

Anyhow, if you decide to try the "Salzsäure": "Salzsäure" is most often sold in a 30% solution. I prefer to dilute this to a 15% solution, to get a mix I can supervise ....

BUT REMEMBER: always pour the acid SLOWLY in the water, when you mix it ... never the other way around.

(how to remember: acid may react heavily with either the water, or the impurities in the water, and cause a minor "explosion" when you start mixing ... what's worst then: an explosion of water, or an explosion of acid? ;-)


And if you don't have a pair of goggles, turn away your head while doing so ... it may not cost you your sight to get a splash of acid in oyur eyes, but it sure does hurt as h... ;-)

 

oder einfach einen salzsäurehaltigen urinsteinentferner nehmen, zb den von dr. becher, welcher bei metro erhältlich ist. da ist schon verdünnte salzsäure drin (15%) und das ganze ist zu nem vernünftigen preis erhältlich. denkt daran, daß die beißenden dämpfe ungesund sind und deswegen das ganze in einem gut durchlüfteten raum oder besser noch im freien stattfinden sollte.