Is there anything I can do to keep wood from cracking? I was making a bird house. I had to stop and got tied up for a while. I went back out 2 or 3 days later and it had a huge crack. The first picture is when I was working on it and the second picture is after three days of just sitting on the lathe.

Using wet wood you have to expect cracking.  Had you wrapped it in plastic while you were away from it would have prevented it until you did let it dry out.  Leaving wet wood chucked in the lathe causes rust at the connections.

A piece that contains the "center" of the branch tends to crack more often than a cut from the "side" of a larger piece.  If you can complete the turning, all at once, it also reduces the chance of cracking. There used to be a fellow ("Trifern") over at LJ's who turned all his work with green wood. He turned it very thin and said he didn't have a problem with his turnings cracking. I guess the thinner the turning the less the stresses.

 

Dan's suggestion of keeping it in plastic will help slow down the drying and help prevent cracking. I fill a plastic grocery bag with the wet shavings and tie it around the turning so the turning is packed in the shavings. That's sort of difficult when the turning is between centers but works OK when the piece is in a chuck. For stuff off the lathe, I do the same except uses a paper grocery bag. The paper bags breathe more and have less of a chance of have mold produced.

 

As Dan pointed out, there can be rusting problems when a green piece is left on the lathe. I ruined the finish on my Nova chuck helping a friend turn a piece of green walnut. He didn't get it completed and was supposed to return the next day. As usually happens, life got in the way and the walnut stayed in the chuck for several days. When I removed the turning, my chuck had rusted and the chrome finish on the jaws was destroyed. I really have to be careful using the chuck so it doesn't discolor new turnings. I should replace the jaws but I'm saving for an Easy Wood Tools chuck!

 

Dan and lew both gave good advice. To be truthful you did just about everything you could to make that piece crack. Opened it up and left it exposed to hot dry air. Lew also touched on the rust issue. leaving wet shavings on your ways is also a no no. Certain woods like walnut will rust them up in just a few hours.

 

Steve

Turning would have done better if hollowed and left on lathe ,but like everyone else I do not recommend it. Even with the bag rust happens and with no hollowing done the moisture comes out faster on the turned portions which makes the whole form warp and split.  When turned thin you can use compressed air to blow out a great deal of the moisture left in the turning. I have taken turnings off the lathe and wrapped in plastic and replaced on lathe the next day with only a small change in the tenon. Any interuption can lead to problems so best to get the first turn done or complete it in one turning. 

Thanks for all of the advice and tips. I will try some new things out and see if it helps.