If you live in a humid place, like me, Wales is just about the dampest part of the Uk, everything goes mouldy around here. Then best not to use woods like hickory that take in damp easy, use the bow wood that suits the environment, oily woods are the best, ipe doesnt seem to take in water what ever the weather. I gave up on hickory. Once its took a set only heat treating will reverse it, not bending it back, this make it worse I believe. Halfeyes recipe is better than poly varnish too, poly varnish just seals it in