How far gone can sourdough starter be and be brought back to life? Mine has been forgotten in the fridge for a month and now has black liquid on top
It is not bad unless you see pink. Black if fine and it should start bubbling after it is replenished.
Toss all but half a cup, add a cup of warm milk and a cup of flour to the half cup. Repeat a couple of days and it should be back to normal.
I read an article about getting a starter going from a dig in Egypt. The starter was dried and thousands of years old.