When I opened the boiler on my La Pavoni PUB Automatic, I was surprised to see charcoal black scale on the inside. This scale is hard, thin and uniform. To look at it, you'd think it was flat black paint applied up to the water fill line.

So my questions are: What is this scale, do I need to get rid of it, and if so, is there anything I can safely use?

A couple more data points: I live in an area where the city water is entirely surface water and is very very soft, and my attempts to remove it with a scrubby pad didn't even put a dent in it.

Any suggestions appreciated.

I'm no chemist but have seen what you have described in several boilers. I believe it is the normal reaction with certain water types and the boiler metal compounds. Not necessarily scale but more like a chemical reaction. Nothing to worry about as long as it doesn't affect taste. If you were able to remove it- it would most likely manifest itself again. I wouldn't sweat over it.

It's not scale. Scale would be white.
What is the boiler of the La Pavoni made out of?

Aluminum boilers tend to get a coating of aluminum oxide built up which actually protects the wall of the boiler from the water.
I don't know what the LP boiler is made of or if it does something similar.

zazenmaster wrote:When I opened the boiler on my La Pavoni PUB Automatic, I was surprised to see charcoal black scale on the inside. This scale is hard, thin and uniform. To look at it, you'd think it was flat black paint applied up to the water fill line.

So my questions are: What is this scale, do I need to get rid of it, and if so, is there anything I can safely use?

It could actually be milk, have a little check of the vacuum breaker, make sure it's not sticking.

Probably not milk, that gives you a stinky foul tasting boiler water. If the water tastes and smells fine, it is probably some kind of oxide that has formed on the brass boiler.