Michael Dresdner

straight talk about wood finishing

Archive for August, 2010

Acetone and the VOC question

Tuesday, August 31st, 2010

Q: I found some conflicting information on thinning nitrocellulose lacquer. Some very good finishers use straight acetone while others write of using lacquer thinner. I realize lacquer thinner is a soup so there are many possible formulations, but generally I was wondering how acetone might behave differently from thinner. A: Acetone, a ketone, is one [...]

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Glazy days of summer

Monday, August 30th, 2010

Q: I’ve stained and sealed with Zinsser SealCoat and plan to glaze with a Van Dyke oil-based glaze. I wanted to top with Zar Interior Polyurethane antique flat, but Zar says polyurethane will delaminate off either the glaze or SealCoat, which has no wax, but may contain stearates. Now what? A: First, SealCoat contains no [...]

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Epoxy over shellac

Friday, August 27th, 2010

Q: Can epoxy go over shellac? A: It depends on the epoxy. Most contain either alcohols or amines, either of which will bond to shellac, but because epoxy formulas can vary so widely, it would be best to either know more about the formulation you are using, or do a sample followed by a cross [...]

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Stiffness to mass

Thursday, August 26th, 2010

Q: I am building my 10th guitar and am using epoxy over bare Indian rosewood to fill the pores, with great success. Can I also apply epoxy to the soundboard to eliminate “spruce ripples” and also fill voids in the rosette? A: You can, but I would not advise it, though it might make an [...]

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Thin enamel

Wednesday, August 25th, 2010

Q: Can I thin enamel for spraying, and if so, what solvent should I use? A: Yes, but you will have to read the label to find out what to use. Because the term enamel is used for many types of coatings, you must know what type you are using to know the thinner for [...]

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What’s in a name?

Tuesday, August 24th, 2010

Q: How does enamel differ from lacquer? A: The term lacquer refers to how a finish dries. Specifically, it means a coating that dries solely by solvent evaporation. It does not give any clue to what resins were use in it, though of course, certain ones are particularly common. The term enamel has no definitive [...]

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Over pre-catalyzed

Saturday, August 21st, 2010

Q: Can you apply brushing lacquer over sprayed pre-catalyzed lacquer? A: That depends on the pre-catalyzed finish, and how long it has been cured. In some cases you can; in others you risk cracking and wrinkling. Because it is so risky without knowing a whole lot more about the particular coating involved than anyone outside [...]

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Lacquer vs. oil based

Friday, August 20th, 2010

Q: You make a distinction between lacquer and oil based finishes. Why does it matter? A: Lacquer, which is a category that includes shellac, is an evaporative finish. It cures solely by the solvent evaporating. That means the molecules floating around in the solvent when it is in its liquid form are exactly the same [...]

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Oil based lacquer?

Thursday, August 19th, 2010

Q: Can I put oil based wiping polyurethane over oil based spray lacquer? A: The simple answer to your question is yes, you can put oil based polyurethane, whether wiped, brushed or sprayed, over almost anything, including lacquer. For the record, though, lacquer is, by definition, an evaporative finish, while oil based finishes are, by [...]

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Rattle cans are cheaper

Wednesday, August 18th, 2010

Q: We’d like to spray Rustoleum hammer finish but do not have any equipment. Can you recommend an inexpensive HVLP system for home/light use? A: Yes, but I’d advise against buying a spray system just for this one job. You can buy Rustoleum hammer finish in aerosol cans under the Universal label. http://www.rustoleum.com/CBGProduct.asp?pid=180 Those Universal [...]

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