Unfortunately I have forgotten most, if not all, of my HS/College Chemistry... But according to a piece of software I have called CASC Solution Calculator, to create a 30% w/v CaCl2 solution, you would use 150g of pure CaCl2 in 500ml solution. (400ml water, add 150g CaCl2, stir, then fill with water to the 500ml mark.) It seems that most of the cheesemaking shops sell 30% solution, but I bought mine at the local homebrewing/winemaking shop and it came as a powder so I've been curious about that. Anyway, hope this is helpful to someone!