Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Interesting i just thought blackening was caused by heat what concerned me was after dipping in vinegar or Cillit Bang for a few mins then using a clear glass with water you could see the dirt coming off into the clean water when rinsing which made me think would that be going through the engine maybe boiling the water of a few time might cure it
Would be nice to know the answer