I recently applied a coat of water-based polyurethane on bare plywood and I'm considering switching to an oil-based spar urethane for extra durability. Is it possible to apply the oil-based finish directly over the water-based one after lightly sanding it? I'm planning to wrap the plywood in carpet and install it in my truck, which will be exposed to varying temperatures. What should I keep in mind?
4 Answers
Yes, you can, but make sure the water-based polyurethane is fully cured before you proceed. Also, don’t just lightly sand; give it a good sanding and don’t miss any spots. After that, wipe the dust away with a tack cloth before applying the oil-based spar urethane.
Thanks for the input! Should I stick with the water-based poly instead? I'm worried about the durability since it’ll be under fluctuating temperatures.
I’ve heard it’s usually not ideal to put oil over water, but some recent formulations might allow it. If you do go that route, I suggest using a coat of dewaxed shellac in between. Just remember, oil finishes are meant to soak into the wood for added durability, which might not happen if there's already a film finish.
Sure, you can do this, especially if you’ll be wrapping it in carpet and keeping it protected inside your truck. But honestly, it might seem unnecessary since you won’t be able to see the spar urethane under the carpet anyway.