Chlorine: The Silent Killer
Role: The Steriliser
Function: Bacterial Inhibition (Negative)
Spec: Cl / NH₂Cl (Chloramine)
If you are doing everything right but your starter refuses to rise, look at your tap. Municipal water treatment is a triumph of public health, designed to kill bacteria.
Your sourdough starter is bacteria.
The Chemistry: Chloramine vs. Chlorine
Modern water treatment often uses Chloramine (a combination of chlorine and ammonia) rather than simple Chlorine.
Chlorine: Volatile. It will evaporate if you leave water sitting in an open jug for 24 hours.
Chloramine: Stable. It does not evaporate. It stays in the water and inhibits the growth of wild yeast and bacteria.
The Interaction: The "Clean" Death
Chlorine doesn't cause a dramatic failure; it causes a "failure to thrive." Your starter may bubble weakly but never double in size. The population is constantly being knocked back by the antimicrobial agent in every feed.
The Protocol: Filtration
The Test: If you suspect your water is the issue, buy a bottle of spring water. Feed your starter with it for 3 days. If the activity explodes, your tap water is the culprit.
The Fix: A standard carbon filter (like a Brita jug or fridge filter) effectively removes both Chlorine and Chloramine. Boiling water does not remove Chloramine.