Michael Dresdner

straight talk about wood finishing

Archive for the 'clear coat' Category

Compatibility

Thursday, September 2nd, 2010

Q: A friend told me that he used nitrocellulose sanding sealer on wood, and then finished it over with an automotive two part clear coat. Does this seem possible? To me it just sounds like the two different systems will not go together.
A: You are correct in worrying about incompatible systems, but as luck would [...]

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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 component [...]

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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 stearates [...]

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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 hatch [...]

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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 interesting [...]

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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 the [...]

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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 once [...]

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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 definition, [...]

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You make me blush

Wednesday, August 11th, 2010

Q: My painter sprayed lacquer recently on a hot and humid day and trapped moisture under the finish. Having had experience with this I told him to re-spray with lacquer retarder added to the lacquer and to remove the humidity from the room before re-spraying. This worked to a certain extent but still did not [...]

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Just a shmear

Friday, August 6th, 2010

Q: If I brush on a final finish, will it cause water based dye stain to bleed into the finish on the brush and smear?
A: Water soluble dye can bleed onto a brush loaded with waterbased finish. Whether that will be enough to smear the stain also depends on your brushing technique and how aggressively [...]

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