Hi all,
I recently was finishing a number of Baltic birch cabinet panels before assembly. Some of these panels were being finished with water-based polyurethane, and others were being finished with an oil stain and oil wax (Osmo polyx).
I accidentally applied polyurethane to one of the panels that was supposed to be oil stained and oil-waxed. As a result, I waited for the poly to dry and then used my ROS and 150 grit sandpaper to remove the poly.
My plan was to finish sand the piece to 220, but I was surprised when I finished with the 150 to have a panel that felt and looked noticeably smoother than I am used to with 220 grit. Since Osmo recommends sanding to lower grits if possible in order to receive the oil-wax better, I stopped at 150 and applied my stain and finish. The end result is a panel that is nicer than any other I've finished with my normal "correct" technique.
My guess is that the accidental application of the water-based polyurethane raised the grain and that then using my ROS removed the raised grain "whiskers" to leave a very smooth finish. The oil stain and oil-wax finish did not further raise the grain.
This all leaves me wondering if I should always purposely raise the grain before finishing with oil. The product instructions for my oil products do not mention this step, and the advice I've seen on Youtube (example) and elsewhere discusses raising the grain as a technique to help with water-based finishes, not oil-based.
So when should grain be raised and sanded on purpose before finishing, and when should it this be avoided?
Thanks for reading