Auto Body Filler Works on Cracks, Holes in Wood
For years I’ve been pushing polyester auto body filler as one of the best materials there is for filling holes, dents, cracks and gouges in wood. Reasons? It’s easy to apply. It sets up in a matter of minutes, never shrinks or cracks no matter how large the repair, it sands easily and finishes very well.
Its only real drawback? Depending upon the brand you buy, it usually comes out a gray or dirty grayish pink. That’s not exactly the shade you’d look for if you want a good wood-tone color match under a clear finish. For this reason, I normally use the stuff only when I plan to subsequently cover it up, with either a couple coats of paint or perhaps some plastic laminate.
Not long ago, however, Minwax came out with a product called High Performance Wood Filler. Like polyester auto body filler, it comes in two parts: a can of putty and a tube of hardener.
As soon as I saw it on the hardware store shelf, I surreptitiously popped open the can and took a look. A quick sniff revealed the telltale odor of polyester. The color was, if not a perfect wood-tone, at least in the neighborhood. I’d call it a warm, brownish gray. Not only that, according to the label, this stuff could be stained! Although it cost about three times as much as auto body filler, it sounded good. I decided to buy a can and compare it to my old standby.
I quickly discovered that it handles just like auto body filler. As with auto body filler, the goo in the can is composed of a liquid resin combined with powdered fillers to create a puttylike material. As with body filler, the two components tend to separate with storage so it pays to stir the can before use.
After stirring, scoop out a blob big enough to handle the job you have in mind, and mix it with a bit of the hardener from the separate squeeze tube. Body fillers usually come with a rusty red hardener. This makes it easy to see when you’ve done a good job of mixing, but it also gives you that dirty pink color mentioned earlier.
The hardener with the Minwax filler is basically colorless. This makes it a bit harder to judge how well you’ve mixed your putty, but it also avoids that sickly grayish pink.
Once either product is mixed with its hardener, you should apply it without delay. Depending upon how much hardener you’ve used, and the ambient temperature, the mix may set up pretty quickly. Use a flexible putty knife and hold it at a low angle. This helps force the putty into the defect you are filling.
Since neither product shrinks, there’s no need to overfill as you must with many other products. Just smooth the filler on and level. Avoid holding the knife at a steep angle, however. This tends to drag the filler out of the defect and you won’t get a level coverage.
On with the tests. Once my samples were mixed, I applied them to shallow one-inch holes drilled into ordinary pine. Ten minutes later, when the samples had set up, I tried staining them. According to the Minwax directions, you should sand the filler lightly with 100-grit paper (finer paper closes the pores of the filler so it takes less stain) and apply your stain while the filler is freshly cured. You should then let the stain penetrate for an hour before wiping off the excess. I followed those directions on the Minwax filler, using a Minwax stain. And while I was at it, I tried the same procedure on my grayish pink auto body filler samples.
Results? To my surprise, once the stain was on, there wasn’t much difference in color between the two products. The auto body filler was just a tad pinker than the Minwax filler, but to be honest, neither was really a very good match for the color of the stained pine surrounding the test patches.
Of course you will probably get different results with different stains and different woods, but my initial reaction is that neither body filler nor the Minwax wood filler is a good choice if you want an accurate color match under a clear finish. For accurate color matching, you’ll probably get a better job with stick shellac, or a product such as Plastic Wood, especially if you take the time to blend two or more colors together to get the exact shade you like.
But for filling under paints or laminates, for repairing plaster and wallboard, for anchoring screws, and working indoor or out, polyester fillers are still my first choice. And given its clear-cut price advantage, I’ll stick with ordinary auto body filler, stuff with names such as Bondo, White Lightning or Black Knight.
