Viable calcium chloride

[Lloyd]

Yes, the whole reason for the issue is my need to change milk supply, moving over to a local diary (P&H) rather than supermarket (P only). With the local milk, the curds are so bad, and the CaCl has almost no effect, even at ridiculous concentrations.  The supermarket milk produces reasonable curd, and even though I always add CaCl, I've never been convinced that it has made a difference.  I still get a degree of shattering, but I can live with it. Culture is ok - I did a side by side test with the two milks.

[awakephd]

Lloyd, I would suspect that the local dairy is pasteurizing at a higher temperature. If so, you will never get the curds to work, regardless of the amount of CaCl or rennet.

[mikekchar]

Yeah, this is the key point, I think.  CaCl2 only adds calcium ions that get precipitated out when the milk is heated in pasteurisation.  If the milk protein is damaged due to higher temperature pasteurisation, or poor handling (i.e. being too old, some kinds of infections prior to pasteurisation, etc) there is nothing you can do to recover.