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How much does polyurethane darken the wood?

Posted by johnnieb (My Page) on
Fri, Aug 15, 08 at 14:22

As part of a major home renovation project we just had our floors (original white(?) oak floors, 1927 house) sanded and refinished. The floor guys had sanded part of the floor in one bedroom and applied several different stains to show us what some of our options were. The old floors were a very dark brown but we really preferred the light color of "natural" that they showed us, so we specified that. The floors had been badly damaged over the years (in part by somebody's bad DIY sanding job in a previous renovation) but after sanding they were beautiful and incredibly light-colored; it was amazing how much it brightened up the house!

We knew they would be darker when finished but when we looked in last night, the floors were surprisingly dark--not nearly as dark as previously, but much darker than we expected; my first thought was that they had used one of the darker stains by mistake but our contractor says there was no stain at all, just the polyurethane on unstained wood. So... just how dark will polyurethane, with no stain, make a newly sanded oak wood floor? And can we expect the floors to lighten much once the polyurethane is completely dry? We looked in again this morning and the floors seemed mostly dry, but the color doesn't seem to have lightened much, if at all.

Follow-Up Postings:

RE: How much does polyurethane darken the wood?

Oilbase polyurethane will darken any wood it is applied to. Waterborne polyurethane will not darken in the same way. For the lightest effect choose waterborne wood floor finishing systems.

Your floor may lighten some as the polyurethane cures. Even waterborne polyurethanes will lighten after several days of curing.

RE: How much does polyurethane darken the wood?

Thanks, checking it out tonight it does look like it has lightened somewhat, but still not as light as we expected. I'm wondering if they used oil-based rather than water-based polyurethane (as they said they were going to) because the fumes were very strong when we looked in yesterday, and penetrated to the basement (where we are living while this is going on). Fortunately today it seems to be dry and the fumes are mostly gone. I guess oil-based wouldn't dry in just 24 hours?

RE: How much does polyurethane darken the wood?

Oilbase would still be offgassing and you'd be able to smell those hydrocarbons (smells like mineral spirits, paint thinner...that kind of smell). Waterborne is about 85% cured in 48 hours and totally cured in about seven days. They too can have a strong smell if the building is closed up after the finish is applied, but nothing as strong as oilbase. Oilbase would still be rather soft and slightly sticky.

Moisture cure finishes are extremely strong fume producers and their odors would be gone quickly as well. However, few people work with that stuff anymore.

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