I receive many, many questions about whether our wood is green or kiln-dried, most frequently from newer turners. I must say, I was in the same boat years ago when I first started turning. I didn't want to deal with waiting for a blank to dry after rough turning and all that goes with that process. Then I bought a 2" thick piece of White Oak about 12" square that I was going to turn a platter from. I mounted that piece on my face-plate and it kicked my tail trying to turn it, it was hard as a rock!
So, after that exercise, I deemed it in my best interest to learn more about turning wood in various stages of dryness. I must say that the very first time that I mounted a large green bowl blank, and those long beautiful curly shavings started to pour off my gouge, I was hooked! One of the best sources that I found was a book called "Turning Green Wood" by Michael O'Donnell. I like this book so much that I bought a small supply for anyone who couldn't find them in their local bookstore. It is available online at Amazon or Barnes & Noble.
Lumber is very difficult to dry in thick pieces, due to the length of time involved and the fact that in order to reduce cracking, the wood inside the block needs to dry at about the same rate as the outside of the block. Commercially, kiln dried lumber is usually not available thicker than 2″ and most often only as 1″. Basically, roughing out bowls allows a block of wood 3″ or 4″ thick to be reduced to about the thickness of 1″ lumber, only in the shape of a bowl. This reduces drying time dramatically, as well as checking or cracking. If you want to turn large bowls from solid timber, you must learn how to turn and season green wood.
How you season a rough-turned bowl is the subject of thousands of conversations and web posts. If you ask 50 turners how they do it, or the best way to do it, you will probably get 100 answers. The simplest and best place to start would be to take your rough-turned bowl off the lathe, put it into a brown paper sack or box and pack it in the shavings that were created while turning it. Now every few weeks you can check the weight of the rough-turned blank to see if it is still losing weight, once it no longer loses weight, it should be dry and ready to remount on your lathe to finish turning.