Tinted Waterborne Over Shellac Seal Coat

Improve the look of waterborne poly on dark wood quickly and easily. Warm the wood's appearance by tinting the poly with amber-colored dye. Bring out the wood's natural color and figure by applying an initial coat of dewaxed shellac. Using both techniques dramatically changes the wood's appearance.

Raised grain, the morning after.

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On a large surface, lay on the finish in successive, slightly overlapping end-to-end strokes, each about as wide as your pad or brush. Wet the surface with the first pass, go back over it only once to smooth and level the finish and then move on. Work fast and don't go back.

sandpaper, sand the surface lighdy, so yon remove onh the raised wood fibers, stop sanding as soon as the wood feels smooth. Sanding too much creates new wood fibers that will raise up when the finish goes on. It's a lot like- shaving. Von want to remove the hair that stands up, bin stop before you cut into the skin!

Does waterborne poly contain harmful solvents?

Although waterborne polyureihanes have little odor, they still contain volatile organic compounds (V()(is), just like their traditional oil-based counterparts. The difference is that waterbornes have far fewer of them.

For example, lacquer typically contains about 75-percent solvents and about 25-percent solids. The solids make up the finish that will remain on the wood after the solvent evaporates. Waterborne coatings generally contain 10-percent solvents or less, and as much as 35-percent solids, with water filling in the rest. Willi such a small percentage of solvent, you don't need as much ventilation as you would with lacquer. However, you still need some. If you spray, list- your spray booth; if you brush, crack a window and run a fan on low speed. Always wear a mask equipped with organic vapor cartridges.

Why are there bubbles in my finish?

Air bubbles trapped in the finish are one of the more vexing problems associated with waterborne coatings.

You can usually minimize the- problem with good application technique. First, don't brush too hard or fast—that's sure to generate air bubbles. Stick to a smooth, gende application technique and use paint pads and bristle-free foam brushes when you can. Still, clusters of very tin\ bubbles, oiled "loam," sometimes show up in the dried finish. Hie result, particularly in gloss finishes, is an uneven, hazy look that no amount of rubbing or polishing will remove. You can often minimize these pesky air bubbles by Stirling about an ounce of half-and-half into a quart of finish before you apply it.

How do I avoid brush marks on large surfaces?

Use a paint pad or foam brush. They're less likch to leave marks than a bristle brush. Part of the problem, though, is that waterborne poly dries so fast, there's no time to 44work it out." especially over a big surface. In fact, going back and forth will only make the finish look worse.

Another problem is applying too thick a coat on each pass. Put on only as much «is you need to get the surface entirely wet. This is true whether you are spraying, brushing or using a pad.

If you must, you can slow down the drying time a bit b\ adding an ounce of propylene glycol to a quart of finish. You can get propylene glycol from a chemical supply house or at most cigar stores, because it is used to charge the humidification devices used in humidors.

Add half-and-half to counteract "foaming," tiny bubbles that can form in the finish and get trapped there as it cures. Don't worry; half-and-half, like waterborne finish, dries clear.

On a large surface, lay on the finish in successive, slightly overlapping end-to-end strokes, each about as wide as your pad or brush. Wet the surface with the first pass, go back over it only once to smooth and level the finish and then move on. Work fast and don't go back.

American Woodworker 73

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  • THORSTEN
    How to finish shellac?
    9 years ago

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