Aluminum, Chlorine, and Philadelphia Water

Factual Questions
1

Okay, this is really several questions about my espresso pot. It’s made of aluminum.

  1. When I leave (Philadelphia) water in the bottom portion overnight, it sprouts growth of some kind. What is this? What’s in Philadelphia water?

  2. Why does chlorine strip the surface of an aluminum espresso pot?

  3. Does everybody still do the “Hi, Opal” thing at this point?

  4. Why does chlorine bleach crackle when left in the bottom of the pot?

2
  1. The growth might be precipitating carbonates from the water, or, if the water is acidic, it might be aluminum salts. Does the inside of the pot look pitted? If so, you might have a pH (acid) problem.
  2. Chlorine reacts in water to form hydrochloric acid. If your water is too strongly chlorinated it will eat holes in aluminum. If it’s only a little bit acid, it will just remove built up calcium deposits and leave you with a clean shiny surface.
  3. Only after having too much espresso. :slight_smile:
  4. Chlorine bleach breaks down into sodium chlorate, which is a powerful oxidizer. It will react explosively with aluminum or organic matter when you heat it. That could explain the crackling, or it might just be a coating of lime on the bottom of the pot drying out and cracking.