Choosing oil or water-based urethane

Q: I’ve contacted a few hardwood refinishers in the Winnipeg area to do the birch floors on the second floor of my house. I’m uncertain whether to go with an oil or water-based urethane. Some contractors say they only do water-based, others say that they have not been happy with the results of water-based urethanes.

What do you recommend? We have a couple of cats, so I’m concerned about how the floors will show scratches.

A: After 32 years, I am still sifting through the propaganda regarding water based finishes.

Here are a few things I can tell you for certain. A good quality water based finish, with cross linker is at least twice the cost, if not more, than a good quality oil based polyurethane.
The apparent advantages of water based finishes:

1) Very fast drying and curing with low odour. Of course, from the point of view of the one applying the finish, this fast 2 drying also can make these products very difficult to deal with, even for the professional.

2) Dries crystal clear and is said to offer greater resistance to ambering. Personally, I find such finishes can be so clear that they add no warmth, or do not allow the true warmth in the wood’s natural colour to come through. there are good quality oil based finishes that also contain a resin from safflower oil which also resists yellowing but still provides a nice look

3) Good quality water based finishes claim superior hardness when you get a good film build. No doubt this is true. However, I have never seen an oil based finish pulled off a floor with masking tape as I have seen with water based finishes.

All things considered, my money in most cases still goes with the oil based finishes, which, if properly applied, offer excellent durability and resistance to spills. A couple of exceptions would be: Certain species of wood can react badly to the solvents in oil based finishes, as can old floors that have been waxed for years. The mineral spirits in the oil based finish can activate wax residue that has seeped between boards, and sometimes, though more rare, into the grain of the wood and create quite a problem with drying and bonding. In these cases, the water based finish is the better choice in my opinion.

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