Well, it's not actually "canning" per se, but I bought a bunch of butter on sale (1.75 $/lb) and made a batch of ghee. That'll keep for years, unlike bottled butter, which I'm told goes rancid within a year. Or maybe not. Anyway, it was 7 lb butter and it produced 6.5 pt, which is 1.85 C/lb, not 1.5 C/lb which is the number I found on the interwebs. It took about 2 hours, start to finish, to cook the water out of almost a gallon of butter.