Swedish Acid Cured Finishes And The Moisture Cured Poly


I’m having my oak floors refinished (living room, stairs, bedroom) and the refinisher is offering to do Swedish, water based urathane or solvent urathane. My choice. He claims water based is superior to solvent based urathanes. Swedish is best but is smelly & takes longer. I’m leaning towards water based fo several reasons. Shorter finish time, easy to repair/recoat. (I own a custom millwork/scenery shop & am comfortable applying finishes). I actually use a floor finish product, Benjamin Moore’s Stays Clear, a water based urathane. We use it for stage set flooring. Which would you recommend? Also can I use a water based product over an existing finish if I scuff sand first? I need to repair several areas in the kitchen & dining room. Thanks in advance for your help.



Dear Michael

There is a basic choice these days between the Oil Modified Polyurethane, and the Water Based Finishes. And yes there is the Swedish acid cured finishes, and the Moisture Cured Poly. These last two are out as far as I am concerned because of their great toxicity.

So here we go : water based finishes can be better or a whole lot worse than the standard 3 coats of Oil Modified Polyurethane. Let me explain. The few reputable brands of oxygen cross linking water based finishes should be as durable as the OMP. And there should be no doubt that the professional catalyzed water based finishes will outlast most all other finishes by a long shot. But most of the catalyzed water based finishes are really expensive, and you have to use a very poisonous catalyst hardener. These are really only used in commercial and gym floor applications.

But now there are the brands of water based finishes that are sold in stores. They are generally the weak kneed acrylic based finishes ( Benjamin Moore ), with no hardener additive. These are not really floor finishes, but just light duty wood finishes, and are generally sold as such. These tend to last only a few years at best. These are cheap to apply, but are not worth anything in the long run.

That said, my greatest objection to the water based finishes is their pale bluish white film, and the fact that some will cloud more when they age. But if you read my article in the Floored News, about the Dura Seal 1000 water based finish, there is the promise that these oxygen cross linking formulas have the best of both worlds. If you use 4 coats of this material, and scuff sand well between coats, you should have a finish that will wear about as well as OMP and will have a pleasant amber tone to it. We still don’t know just how well this finish is going to age, only time will tell. There is some concern that the emulsifiers in all water based finishes stay in the film and make the finish opaque in just 3-5 years. I saw a job done with a store brand water based finish on maple, and this was happening after only 3 years. It was such a gradual change that the owner did not see it, but the fine grain of maple was just about obscured.

I still use Oil Modified Polyurethane on 90 % of my floors, with great (24 years and counting) results. Just be sure use no lacquer or oil sealers. And be sure to Brush on the coats of OMP for a real bubble free finish. I just finished a detailed article on how to use the Oil Modified Polyurethane for the directory subscribers, and believe me it is not a quick and easy process, but worth it. You can buy an email copy of this with a small donation to the site, just ask.

Oh, and just read the first part of the cleaning article in the Floored News section, to see just what needs to be done to keep these new finishes glowing. And this article describes how to identify and old finish, so that you can use the same finish to touch up. Never use a water based finish over an oil based finish.

As always your Most humble servant, Joseph, the Wood Floor Doctor.