Hello -- i am restoring an old S-series rancilio (Rebuilding a Rancilio S26). I have been rinsing out my HX with water and acid solution to descale the inside. I pour the water out from the HX into a glass an inspect for scale debris. Today i noticed this material come out of the HX. Any one know what this is? It doesn't look like scale to me. Its just a red/cooper colored flake. Its very very thin.


Also, the the underside of the boiler lid looks to have a coating on it. It has flaked off in spots and i was wondering if any one knew what this coating was?


thanks!

I believe the black coating is copper oxide. It's protective of the copper underneath. Have you read this thread: Descaling copper boilers--something NOT to do!!!