I recoated a strip to fix a scratch and the sheen is completely different. I did everything identical to the final coat (even the same can of finish). What’s the cause?
Don Jewell, head of technical at Wadesboro, N.C.-based Loba-Wakol LLC, answers:
I wish this were a new or unique question, but if you have been finishing and repairing wood floors for any length of time, you have dealt with this issue.
Things that will affect sheen level include (but are not limited to): the amount or lack of matting agent, whether it was mixed well enough, the thickness (in microns) of the finish film, and amount of hardener/cross-linker.
For the sake of this discussion, let’s say we are dealing with a repair on a satin sheen finish coat. If everything is perfect and you continue to add layers of satin finish coats, you will eventually appear closer to semi-gloss. As the mil thickness increases, the thicker layer has a harder time reflecting and refracting the way the light plays off the floor.
The best way to “hedge your bets” for a successful finish repair is to apply the repaired area exactly the same as the finish around it. So, if you just lightly abrade the repair area and apply a nice heavy coat like you applied the original finish, then your film thickness will be greater than the remaining floor and will likely appear shinier. You would need to get the repair area base coats down to the same level as the base coats of the rest of the floor and apply the exact same finish thickness on the repaired area as was applied on the remaining area. At best, we are lucky when it matches perfectly. Remember, we are dealing with microns of difference having a potentially large effect.
When dealing with two-component finishes, the amount of hardener can have a big influence on the final sheen. Having both the original coat and the repair at the exact ratio can be difficult to achieve even when measured by weight on a portable scale and not by volume. Most two-component water-based finishes are a 10:1 ratio (10 parts finish mass to one part hardener/cross-linker). Make sure to confirm this with the product you are using, as it could vary. Measurement by weight is the most accurate method.
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