Heat Marks on Catalyzed Varnish Finishes: These Can Be Impossible to Remove - Popular Woodworking Magazine

Heat Marks on Catalyzed Varnish Finishes: These Can Be Impossible to Remove

 In Flexner On Finishing, Flexner on Finishing Blog

This is a heat mark on a catalyzed finish that resists any type of repair.

I got a call from a long-time client asking me to come by and see if I could fix the heat damage to her dining table. I was actually quite familiar with that table. Twenty years previously she told me about an original Chippendale dining table and twelve chairs she and her husband had just bought from an antique dealer in a neighboring state.

Needless to say, I was really curious. The odds of twelve matching original Chippendale chairs surviving for several hundred years are minuscule, actually even less. So I asked if I could come by to look at it. The couple was in the process of taking everything out of boxes when I got there.

If you have been around antique furniture for many years, as I had, you learn to recognize most frauds very quickly. As I’ve pointed out previously in this blog, faking several hundred years of age requires a huge amount of skill. So I was suspicious.

In this case, it didn’t require any more than just walking into the room and glancing at the dining set to know immediately that it was new.

Nevertheless, I did spend some time looking more closely, just to be sure. The table was only partly assembled, so the husband and I turned it upside down to get a look at the underside. There it was stamped in large black letters: Made in Korea. Very sad. I offered my expertise if they should decide to sue the antique dealer. But they didn’t want to. They still liked the dining set, so they decided to keep it.

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Back to the heat damage. It had been caused by a pizza in a pizza box that had been placed on the table.

A few years previously, I had been visiting my son during a time when he was having a big party. He had ordered half-a-dozen pizzas delivered and had spread them out on the dining table. Later, when he and his wife were cleaning up, they discovered large white marks under each pizza box. The finish on the table was nitrocellulose lacquer, so there were two ways to remove the damage. The easy way was to spray some butyl cellosolve onto the white areas. Butyl cellosolve is a very slow evaporating solvent for lacquer. The solvent puts the lacquer back into solution so it has time to reconstitute itself, and the white areas disappear.

You can buy aerosols of butyl cellosolve that go by a number of trade names often indicating that they remove “blush,” which is the finish turning white. Amazon carries “Blush Eraser” from Behlen’s.

You have to be very careful with this product because if you get the finish too wet, it will introduce fish-eye (craters) if the finish has been polished with a furniture polish that contains silicone, which most furniture polishes do.

So not having access to the aerosol solvent and knowing that silicone furniture polishes were common in that house, I chose to use the other method of getting rid of the white marks: abrade the finish with fine steel wool. It took some elbow grease, but I succeeded. Unfortunately, I didn’t take any pictures.

The situation with the Korean Chippendale reproduction was different, however. The finish was a catalyzed (conversion) varnish. I could tell this by two methods. First, I knew that most furniture made in and imported from Asia is finished with this finish. And second, I did a test on an inconspicuous area by dabbing on a little lacquer thinner. It did nothing.

So I was stuck. A catalyzed varnish is very resistant to damage from anything. But as the finish ages, it can become susceptible to white marks. Think of these finishes as plastics, which they are. Plastics deteriorate. In this case, the hot pizza was too much for it. Still, the finish was durable enough to resist both the solvent and the abrading. There was nothing to do but refinish the tabletop, which I told my client. I just didn’t want to be the one to do this.

– Bob Flexner

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