I have a large piece of wood that was drilled to a heavy slate rock and still had to be weighed down with eight heavy stones to keep it from floating. It took probably a week or two for it to fully soak through, I don't know since I haven't removed the stones and tried to properly set it yet but that was how long it was before the bubbles stopped coming up. Every piece is different though. I have one that's even larger but a different species of wood that sank instantly.