Water Resistance of Wipe-On Polyurethane Finishes

With enough coats, wipe-on poly products can provide good moisture protection. March 12, 2006

I recently built some cabinets and installed a bunch of moulding for a client who wants their friend to put the finish on all of my work. He said he was going to use a wipe-on poly for the trim and cabinets. I don't mind the trim, but the cabinets are in the bathroom and I think it needs better water resistance. I haven't mentioned it to him yet because I wanted to do some homework first. Where can I provide evidence to support my idea, or should I leave well enough alone?

Forum Responses
(Finishing Forum)
From contributor C:
Let it go. A wipe-on poly can be an excellent finish. Assuming good quality workmanship, wipe on poly will be a more durable finish than NC lacquer would be and lots of cab shops still use that. Because wipe-on finishes tend toward very thin coats, they should be applied with more layers (personally, I'd like to do at least 6 coats for bathroom cabs). Fortunately, coats go on quickly with the wipe-on products, helping to make up the time needed for the extra coats. Carefully done, the wipe on poly should perform as well or better than pre-cat lacquer. Not quite as well as CV, but overall, quite satisfactory.

From Paul Snyder, forum technical advisor:
The information you're looking for is known as the 'moisture excluding effectiveness' or 'MEE' of various finishes. As a comparison, 3 coats of catalyzed polyurethane (2K PU) has an MEE of 66%. 6 coats of oil-base polyurethane has an MEE of 62%. With enough coats, oil-base poly offers a lot of protection/durability.

From the original questioner:
Thanks for the info. They were telling me they were only going to do two coats of poly over benite. I'll suggest they go for more coats.