Michael Dresdner

Q: I’m trying to finish a secretary project. I’ve done part of it with General Finishing wipe on semi-gloss urethane and I guess I got lucky, because now I can’t get the same results without dust and debris setting in. If you do a semi gloss finish is there a way to erase the nibs and have a smooth clean result?
A: Yes, there is a way to erase dust nibs, and I’ve talked about it quite a bit in these pages, but there is also a way to avoid them. You can search for “rubbing” and get more in depth discussion, but for now, let’s go over both options at least briefly.
Any finish that is sufficiently thick can be rubbed out, and that process removes dust nibs. Start by lightly sanding with 400 grit or finer paper to remove the nibs, then restore the sheen by rubbing. You can rub to satin using 0000 steel wool and paste wax, or rub to semi-gloss by replacing the paste wax with automotive rubbing or polishing compound. The pairing of polishing compound with 0000 steel wool gives you a slightly higher sheen than steel wool lubricated with wax.
You can avoid all this by how you wipe the finish. In truth, wipe on finish should be called wipe off finish. If you put it on too thickly, it can pick up dust, but if you wipe it off completely, it won’t. That means you need many more coats to get the build you want, but since each coat goes on and off so quickly, and it is so easy to regulate it if you simply wipe off all you can, leaving only the thinnest layer of residual oil varnish, it’s really no big deal. It will take more time, but not more work.

Q: Can I put one coat of oil based polyurethane on some drawers, wait eight hours or so, and then overcoat the oil based polyurethane with several topcoats of waterbased polyurethane?
A: Sometimes. That is to say, some waterbased polyurethanes will adhere to some oil based polyurethanes, but not all will do so. I’d let the oil based finish dry thoroughly (at least 24 hours), then add one coat of Zinsser SealCoat, which will ensure good bonding between the oil and water no matter which brands you are using.

Q: There’s a method I want to try; waterbased dye, seal, gel stain left dark in corners and wiped to simulate wear, top coat. How can I brush top coat using varnish without screwing up the gel, since varnish needs scratches to hold to?
A: No it doesn’t. Just let the gel dry thoroughly so that it does not get moved around by the brush, and flow the finish off the brush as opposed to scrubbing. That technique will allow you to easily topcoat this sort of glazed finish without any problems, and oil based varnish will easily adhere to dried oil based gel stain.

Q: Can I add dry pigment to lacquer to color it?
A: In theory, yes. In practice, it is almost impossible to get pigment powders to disperse uniformly in liquids. When we add them in the industry we use tools specifically designed for forcing pigments to combine with liquids, such as ball mills and high shear mixing blades. Unless you do some formulating on the side, you probably don’t own these machines, and you will find that trying to either stir most pigments into lacquer, or incorporate it with a drill bit mixer, will be an exercise in frustration. In addition to mixing tools, formulators often incorporate dispersal and suspension agents into the mix to keep the pigment from settling too quickly to the bottom of the container, and allowing it to remix easily. Odds are you don’t have access to those ingredients either.

Q: I have a lot of tubes of various oil paints on hand. Could I use oil paints as a pigment to add to lacquer?
A: If you are talking about concentrated oil colors in paste form in tubes, yes you can mix a small amount into lacquer, but don’t try to add too much. Even with just a bit, it will make the lacquer dry slower and set to a softer film; add too much and you will have a finish that takes forever to dry and is very soft indeed.

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Q: I am using McFadden nitrocellulose through a standard spray gun. I just successfully shot my first guitar and am working on another which I would like to tone with a dark opaque to light translucent wine red on the headstock veneer and carved maple top. I am having a hard time determining if I should color the wood before applying lacquer or if I should mix a pigment into the lacquer.
A: First, McFadden has gone out of business, but have no fear; Seagrave Coatings bought their formulas and intends to continue their fine line of guitar lacquers. I’ve spoken with the president of Seagrave and feel quite confident we will be as happy with them as we were with McFadden.
As for the toner, while either can be done, it is far easier to color between coats of clear finish than it is to color the raw wood. However, I would not add pigment to the lacquer; I would add dye. Use an oil soluble dye predissolved in solvent, or use a universal dye concentrate or NGR dye. Enough coats of dyed lacquer will indeed look opaque, so you can get the hiding characteristics you want at the very dark edges. In addition, you can maintain the translucency you need as the corona graduates to the lighter center.

Q: Where can I get information on custom color stain? We can’t find the color we want for an entertainment center. Can you teach us how to mix our own?
A: I can indeed, and in fact, have done so in all four of my books on finishing and many times in magazine articles. However, there is a much simpler alternative that may be just the ticket in this instance. Let someone else mix your custom stain for you. Here’s how.
Go to the paint or home store where you will find a myriad of paint chip samples on the display wall. Find the color paint that is the same as the color of stain you want, and have the clerk mix a small can of that color in low cost latex wall paint. Take it home and reduce it 100%, that is, half paint and half water, and you have made a custom color wiping stain. Flood it onto the wood and wipe off as much or as little as you want to get not only the color you want, but the density of stain color as well. This custom stain is easy to use, inexpensive, and is compatible under just about any clear finish you have chosen.

Q: I’ve been using cellulose sanding sealer on my woodturnings. What’s the difference between it and Zinsser SealCoat, and which is better? I normally use wipe on polyurethane as my finish.
A: Better is a personal judgment you must make, but I can certainly tell you the differences. Cellulose sanding sealer is lacquer laced with stearate, a soft soap that adds loft and thickness to the lacquer. It sands easily and tends to powder under sandpaper. However, some finishes, including many polyurethanes, can have adhesion or compatibility problems with stearated sealers. For that reason, I generally suggest SealCoat under such finishes. SealCoat is pure dewaxed shellac, and although it does not sand quite as easily as stearated sanding sealer, it is compatible under just about any finish, and offers more clarity as well.

Q: Any word on the Lawrence McFadden Seagrave deal?
A: The decision of the bankruptcy court that must approve Seagrave’s purchase of Lawrence McFadden has been postponed until February first. I will get back to you via this blog once that is finalized, but in the meantime, I spoke at some length to Peter Tepperman, the owner of Seagrave Coatings, this morning and he told me he has every intention of continuing to offer the McFadden formulas for instrument finishes, gel urethanes, and other standard line products for which McFadden has developed a fine reputation over the years. The conversation left me very confident that I can now recommend Seagrave Coatings with the same fervor and assurance as I always did with McFadden in the past. I think we have a winning situation. Here’s a link to Seagrave so you can see what they are all about.
www.seagravecoatings.com

Q: I sprayed a very thin final coat of lacquer on a guitar when it was cold and humid, and the finish blushed. I had to spray another coat of thicker lacquer and the blushing went away. I think I understand the reason why blushing forms, air trapped, but what I don’t understand is why thinner lacquer makes it worse.
A: Blushing is not caused by trapped air; it is caused by trapped water. When the relative humidity is high, no matter whether it is hot or cold, you can get blushing. Here’s how it happens.
High relative humidity means the air is holding almost all the moisture it can hold. As air gets colder it is less able to hold moisture. Thus, if the temperature were to drop just a few degrees, you might just hit the dew point; that point at which the air is overloaded, relative to its temperature, and moisture starts to come out of the air as condensation.
When you spray a very thin coat of lacquer, the abundance of thinner flashes off very quickly. This process of evaporation uses energy in the form of heat. Thus, it robs heat of the surface and the immediate surrounding air, making the air just above the evaporating solvent a bit cooler. Sometimes it is just enough to condense the water in that air, and that condensation gets trapped in the lacquer as blush.
It should be obvious now that the way to avoid blush, other than not spraying when the air is laden with moisture vapor, is to slow down the evaporation rate of the lacquer, and in fact, one of the most common blush eliminators is simply slower evaporating solvent. That way you can still spray as thin a coat as you like, but without the blush. Does that help?