There are generally 2 methods to cure meat:
- The older method (I believe) is what I would call "excess salt" curing. This basically involves applying a generous quantity of salt to the piece of meat, together with the spices, and waiting a certain amount of time for the meat to absorb the salt.
- The other method is what I (and others) call "equilibrium curing" in which a calculated quantity of salt is added to the meat, with the spices, and allowing enough time for the meat to absorb all the salt.
While both methods will work, the excess salt method involves guessing, hopefully based on experience, how long the meat should be left in this salt mixture to cure. If it's not left long enough, not enough salt is absorbed to preserve the meat, if it's left too long the end product will be salty. This "guessing" will have to vary based on the percentage of meat to fat in the product (fat absorbs salt less readily), whether the product has skin on it (skin acts as a barrier), the thickness of the product, the temperature of the fridge, and probably many more variables. I've heard people say to leave items for 1 days per kilogram of meat, but that doesn't really make sense as it doesn't account for thickness or fat content. Sounds to me like the old recipes where people were told to cook something in the oven for X number of minutes per pound. It'll work, but most likely you'll end up with overcooked/undercooked food because the variables are not accounted for! Honestly, this type of curing doesn't make much sense to me. I don't see an advantage, but I would be happy to hear from people who do this (and there are many!) to correct me.
I always cure using an equilibrium cure. I use between 2.5% and 3.5% of the meats weight in salt, rub it all over the meat, and put the meat in a sealed bag, flipping it every 3-5 days in the refrigerator to make sure the chunk is always exposed to the brine that is formed by the salt pulling out water from the muscle. After a fairly arbitrary amount of time, but one which is long enough to make sure all the salt i've applied has been absorbed, I consider the meat cured and ready to move to the next phase, into the fermentation box or curing chamber. To me this is much easier than excess salt curing. By applying a known, wanted, quantity of salt, the product will not become over-salted, ever, no matter how long it's left in the fridge. The question is really what the minimum amount of time is for the meat to absorb the salt. I don't really have a good answer, other than "leave it long enough to be SURE it's absorbed the salt". I always leave my items in the fridge curing at least 2 weeks, and for very large things like a culatello, I give it 3. That's the beauty of this system..... you can't overcure! I guess if I'm in a analogy to cooking mood, this method would be the sous vide cooking of the curing world. By cooking a product at it's final temperature, you can't overcook it, and it won't be undercooked if you leave it long enough.
I hope that sheds some light on the different methods, and why I do things the way I do.