Quote Originally Posted by jstraw View Post
the batches that haven't turned purple suggest it's not exhausted. We'll see how things proceed.
Yes, certainly the batches that have not turned purple suggest the stock itself is not exhausted. If the pipets you are using turn out to be the culprit be careful not to contaminate the stock with them.

I use a separate syringe (with plastic tip) to measure both A & B and rinse them thoroughly with hot water immediately after use. They are cheap, easy to clean and seem to be quite accurate.