I have a soft wet wood support beam, as described here. I bought some wood hardener. Instructions say to not apply to wet wood, only dry. I just wonder how that makes sense. I need the hardener liquid to penetrate the wood as much as possible. Water will creep along a wet surface better than a dry surface. I believe the wicking action of a wet surface will get the harder deeper into the wood. OTOH, they must have a reason for the guidance. Is it that the hardener would trap the water inside the wood fibers and be unable to escape?
If I use a hair dryer or something to dry the wood out as much as possible, is there anything I can do to improve the penetration of the hardener? I suppose I could make holes but of course that’s probably a bad idea in this case.
I should also mention that the hardener is water-based, which adds to my bafflement. The PDF says “Substrates must be cohesive, clean, sound and dry.” But the 2nd bullet on the webpage says “Adheres to damp wood”. Webpage also says “Surfaces: Can be applied to any types of woods, absorbent wood, dry or damp, including exotic species, chipboard and plywood sanded or stripped beforehand. … Directions for use: Do not apply to soggy wood.”
It’s confusing but all their statements together seem to suggest it’s okay to apply to wet wood, but not ideal or optimal. Though my intuition would be to favor slightly damp wood to get wicking effects.
alzymologist@sopuli.xyz
answer by Alexander@sopuli.xyz is correct, but I just wanted to add some stuff.
firstly, why they recommend dry wood is that with dry wood, hardener would be sucked in by capillary action. but that is assuming along the grain. perpendicular to it, wood, or plant cell are still filled with water, and if driedthey shrink. but they can not shrink much mostly because the outermost dead layers do not change size, and would help hold the shape. with shrinkage, there would be gaps where fluid could seep into.
also, if you do apply to wet wood, same cells will now try to swell up, but same dead cells will stop from expanding. this will restrict the max amount of hardener that can be be absorbed.
now for some chemistry bits, basically diffusion will occur. In fluids it is called osmotic process/flow, where solvents may move across semi permeable membranes to reduce concentration differentials. wood is not really semi permeable (it is, well, permeable), so both solvents (water) and solute can move. but solute molecules are still larger than solvent stuff, so they do not diffuse much fast (diffusion is roughly proportional to mass). if you have water inside as well as outside, some solute will move in by diffusion, but rate would be less as there is no mechanical pressure gradient. only chemical potential / entropy contributing to free energy. when you have less water inside, there is a mechanical pressure driving flow, and then solvent will drag solute with it. still it would form gradients (solute concentration would be lower as we go inside), but this gives a better shot for solute. And more time is better to ideaaly reach a equillibrium conc.