Couple of weeks ago I bought some rough 5/4 poplar from a local (Bangor Maine) cabinet shop. The boards looked pretty straight and the owner said they had been kiln dried (6-8%). He suggested I keep it in a heated area. As I was going to use it in about a week, I left it stickered in my unheated garage. The humidy was about 35% there, as it was also in my house. The basement was around 50% so I thought it would do no harm.
I brought the wood today to my local high school shop which I have access to and jointed and planed it. A couple of the boards looked a bit cupped but still all were fairly straight, i.e. no twisting or bowing. Ran the cupped sides through the jointer and found after some runs that the ends of the boards were thinner than the front. Not wanting to joint past 3/4″ I settled at that thickness as the boards looked pretty flat.
When I was through, I saw that a couple of the boards look considerably bowed! The shop was very warm but I didn’t think it would have that great an effect in just a couple of hours.
Is it possible that the boards cupped in that short of time or were there tensions in the board present that were activated by the milling? Also, given the 35% humidity in my house would it have been better to bring the boards inside? Lastly, what suggestions for bringing the bowed boards back to (fairly) flat? A good book on wood movement would be helpful as well (not too technical). Thanks…english