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| Leave it to the pro. Michael Dresdner, a nationally known wood finishing and woodworking expert, has answered hundreds of common wood finishing questions in Varathane’s Q&A library to help you successfully complete your project. Click on a link to the left for help and solid advice. |
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| Q: What should I do to prepare the surface before I apply polyurethane?
A: Assuming we are talking about clean, raw wood, sand through the grits, then stain if you need to change the color. Typically I will start sanding at 80 grit, then go through 120 and 180, then follow with a final sanding with 180 garnet paper, by hand going with the grain. If you can’t find garnet, use 220 aluminum oxide. Stain, if you choose to do so, and make sure the stain is dry before you continue with a compatible topcoat. For instance, its usually best to use oil based polyurethane over oil based stain. |  | |
| Q: I have an old maple dresser that was painted, and was originally a deep red finish. How do I remove all the red stain from the wood so that I might stain it a different color?
A: There’s no guarantee that you can. Once all the finish is off, and I do mean all, sand the raw wood to make sure you have a clean surface. If the color remaining in the wood is a dye, you will probably be able to remove it by wiping the piece with full strength laundry bleach, but only if all the finish is out of the wood. If it is pigment stain, the only way you can remove it is by scrubbing with lacquer thinner on coarse nylon abrasive pads, or by sanding, and neither is guaranteed to take all the pigment out. | | |
| Q: I have some dining room chairs that I would like to paint black using a high gloss latex paint. The chairs are solid oak and have a polyurethane finish on them. Do I have to sand or do I have to do more than sand?
A: Neither. Clean the surface by scrubbing with mineral spirits or TSP on fine nylon abrasive pads. The solvent will remove any surface grease or oil while the pad lightly abrades the surface. Add one coat of Zinsser SealCoat, a clear primer, or Zinsser BIN, a white primer, if you plan to use waterbased paint, but if you want my opinion, putting latex paint on chairs is a terrible idea. It won’t hold up well and will be very hard to keep clean. Instead, I would use Universal, a new Rust-Oleum paint that is much more durable. You won’t even need the primer if you use that, since it does not require a primer. | | |
| Q: Is sanding sealer needed under polyurethane on a log bed?
A: Sanding sealer is never necessary; it is merely an option that helps speed up finishing under certain circumstances. This is not one of them. If this is new wood, the answer is a definitive no. However, if the bed is being refinished, you would use a clear primer, like Zinsser SealCoat, only under waterbased polyurethane but not under oil based. |
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