Any milk that has been pasteurized and cold stored should have Calcium Chloride (CaCl) added. The reason for this is because the calcium originally in the milk slowly becomes soluble and cannot be used to form a firm curd. The exceptions are Mozzarella, Provolone and any other cheese that requires stretching at some point in the recipe. This is because the stretch depends on the calcium leaving the curd. Some fresh milks may need CaCl added if the curd is not firm enough due to poor calcium in the milk, caused by either season or poor diet.
This information applies to both hard and soft cheeses.
This bottle of Calcium Chloride is a 30% solution.