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21% MC in blue pine stair treads9/8
I'm having thick blue pine ponderosa stair treads milled for a metal stairway ( 5 1/2" thick, 11 1/2 " wide, 36" long). They will be milled from an old growth log with 21% MC. I live in the arid high desert of central Oregon.
If I had time I'd build a solar kiln and dry them before bringing them inside, but I don't have that time. I'll be bolting them to the metal tread plates using four carriage bolts, and the metal posts for the stairway railing will be bracketed to the edge of each tread.
I know they may develop some checks as they dry, and some shrinkage, and I'm considering those future possible imperfections "character" for the treads.
I know sealing the ends will help.
My questions: Is there a finish or coating I can apply to the entire tread that will reduce or slow the drying process to reduce imperfections once dried? Id there a percentage of shrinkage I can calculate prior to milling?
Thanks! - Dan
No practical effective coating.
I would ask the mill to cut your parts as far out from the heart as possible. If they contain the pith, you will certainly have checks. The flatter the arc of the annual rings as viewed from the end, the less the cupping will be.
There is a formula to guessamate the wood movement. Google or look on this site for wood shrinkage/swelling formula.
You could also try "The Shrinkulator" website: http://www.woodbin.com/calcs/shrinkulator/
Thanks for your responses! the shrinkulator is a great tool!
We have a better calculator for shrinkage and other items too here at WoodWeb. Look at right side top of screen just below kiln club list.
I think there is a product called PEG that is used to control shrinkage as the board dries. Not sure of it's use for stair treads though. It'll likely discolor the wood.