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
Replies
If it is one board then I'd say it is likely stress in the lumber (often called reaction wood). If it is all the stock and they look like they are from different trees, then the enviroment is more likely. I think that you are likely under estimating the difference in humidity between your house and the garage. Unless you have a quality ($40) gauge it is not very reliable. More importantly there is a big difference between 35% humidity at 20 degrees and at 80 degrees. None the less, I think it was the lumber. By the way how bowed are we talking? 1/4" over 8 feet? Or 1" over 5 feet.
Mike
I bought the wood 6 days ago and spoke to the shop where I bought it today. One of the owners said he has seen that happen sometimes and doesn't know the reason why. Some wood, he thought (and said he's not an expert - has worked there only for 30 years and still learning) has a lot of tension in it and when you thin it at all it would bow or cup. Was also nice enough to let me know he would replace what I couldn't use...I haven't had time to take the stack apart to measure the bow but I'd guess at least 1" in 6 feet, enough to make gluing up a top for a storage bench difficult and something I would not trust to stay flat in the future. It might just split apart also,
English
That's a helluva dealer, willing to exchange wood that's just acting like wood!My goal is for my work to outlast me. Expect my joinery to get simpler as time goes by.
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