Michael Dresdner

straight talk about wood finishing

Making an impression

Q: I am pre finishing a large two piece conference table. I finished spaying a heavy coat of my last application of flat pre cat over two coats of vinyl sealer and two coats of flat. The temperature here is in the 80’s with about 28% humidity. I plan on wrapping these tops in shipping blankets laying one on top of the other for a 1500 mile delivery. How long should I wait until the finish is hard enough not to mar or rub?
A: That’s not as simple a question as it appears. There are two variables that you did not tell me, so the best I can do is give you a rubric for figuring it out, and that includes explaining the cure variables you are working with.
First, understand that catalyzed, and especially pre cat mixtures, vary tremendously in cure time depending on their formulation. Specifically, the higher the acid content the faster the cure, but there is no standard. Thus, you need to read the spec sheet; it should tell you when full cure occurs. Typical formulas can range from as little as eight hours to eight days, and that’s for one coat on an already cured surface. That brings us to number two.
Second, this will all change if the four base coats of vinyl and flat were not catalyzed. If they were not, it greatly extends the time needed to prevent blocking. As I said, since I am lacking these critical bits of information, I can’t give you a solid time. However, it won’t hurt to do a thumbnail test. Find an inconspicuous spot and press a thumbnail into the finish with more pressure than you suspect will be exerted by the shipping weight. That will at least give you insight into how the finish is geared up to resist an impression from the pads.