Q. We have recently switched to a water-based finish. When we use it on hard maple, the wood from one supplier seems to cause the sugars in the wood to come through the finish and appear as a white frost on the surface. What is it and why on just one supplier?
A. We probably would have to run an expensive chemical test to know for certain, but I do think I can provide a likely explanation. A couple of facts about hard maple. First, we know that the wood contains sugars and that these sugars are soluble in water. We also know that in most hard maple lumber, the kiln schedule reaches 150F and hotter, which seems to modify the chemical structure in the wood so that the sugars do not bleed out of the wood when the wood is dry.
However, there are some drying operations that reach only 110F maximum temperature, which would possibly mean that the sugars are more mobile in the wood if water (water-based finish) is added to the dry wood. So, check with the one supplier that is producing the troublesome wood and see if they are using an unusual drying system and what maximum temperatures they are using during drying. My guess is that they are not reaching 150F or hotter. Let me know if I am incorrect.
Gene Wengert, “The Wood Doctor” has been training people in efficient use of wood for 35 years. He is extension specialist emeritus at the University of Wisconsin-Madison.
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