Hi, I want to make a basla board and I am very anxious to start. Will high humidity warp the wood? Should I wait until winter when there is almost no humidity? Also, would paulownia be a more stable wood? Thanks for any info!
The great thing about really light wood is, they can get soaking wet and give the moister right back as soon as the humidity goes back down. I’ve had a lift of balsa sit in the rain before, it dries out, too much ado about nothing
Both woods (any wood for that matter) are “stable” if they have been properly dried. Newly milled wood should be stacked flat outside with 3/4" “stickers” separating each board with pleanty of weight on top and covered from sun and direct moisture. For most hardwoods the rule is about one year of drying for each 1" of board thickness. If the boards are to be kiln dried, this outside air drying should be done for a minimum of 3 months before going into the kiln. These are very general rules and climatic conditions have a big affect.
To bring all this home to your subject, suffice to say that your balsa should be “properly dried” before use regardless of the relative humidity in your region at any particular time of year. In other words, improperly dried wood will split, crack, and warp even in the winter months in the Mojave Desert and properly dried wood can be used to make the finest furniture or surfboards even on the coast of Maine or in Hilo Hawaii. So it’s not the relative humidity outside the shop that matters nearly as much as the “moisture content” of the wood. Most often these two issues have nothing to do with eachother.
If you don’t know where your wood came from or its dryness, purchase a wood moisture meter (about $120 and up), or take a board from your lot to a local hardwood lumber dealer and ask them to use their meter to check your wood. Depending on your geographic area you want it down to about 8 - 12%.
You can do a general check by taking a random piece of wood from your lot samall enough to fit in an oven. Weigh it first, then put it in the oven for 1 1/2 hours at about 180 degrees. Let it cool enough to weigh it again. Very generally speaking, wood will dry to about 1/2 its freshly milled weight, so if your sample weighed one pound before the oven and very near the same after the oven, it’s fair to assume that there is not a lot of trapped moisture left in the wood. If the weight dropped by more than several ounces it’s fair to assume your wood has quite a bit of remaining moisture and is not properly dried for use.
We could write a book here, but all this is to say that you need to work with properly dried wood if you care about the results. If the wood is properly dried you can get good results at any time of the year.
Probably more info here than you really wanted, but perhaps others could also benefit by understanding the basics of wood drying. I’ve studied lumber drying and have dried thousands of board feet of lumber over the last 30+ years, including balsa for the few surfboards I have made. As true with any endeavor, mistakes are the greatest teacher. If it’s worth crafting, it’s worth using good dry wood. Enjoy the ride!
Professor Jim,
You made a good point. This winter the barn roof caved in over a stack of over 4,000 bd. ft. of perfectly dry lumber. It all got soaked for over two months before it was noticed. I was sick, but after repairs to the roof, it only took 60 days before the lumber was exactly as dry as before the incident. Soft woods, usually those with wide growth rings and large cell walls) dry much more quickly than dense woods that grow slowly.
But as I know you agree, the whole issue is about getting the wood properly dried first. Once wood is “dry”, relative humidity and occasional direct moisture are not so much an issue because the “trapped moisture” within the cell walls of the wood is already at a minimum. So I agree with you, the outside humidity thing is much to do about nothing.
Thanks for the help guys!