The Effect of Finishes on the Vibration Properties of Spruce Guitar Soundboard Wood

Howard Page Stephens


This paper presents a study of the effect of a sealer and four finishes on the vibration properties of spruce for guitar soundboards.  Two of the finishes, de-waxed shellac and nitrocellulose instrument lacquer, are evaporative finishes, traditionally used for guitars. The third and fourth are reactive shellac-based finishes. The study measured the fundamental vibrational frequency, f0, and damping quality factor, Q, of Sitka spruce test bars machined in along-grain and cross-grain orientations, and coated with sealer and the finishes.  The sealer alone produced significant changes in both f0 and Q for the two grain orientations: the along-grain f0 decreased; the cross-grain f0 increased, and Q for both grain orientations decreased. The finish top coats affected f0 for only the along-grain bars, which decreased with top coat application. Compared to Q for the sealer coating, all of the top coats cured for seven weeks increased Q for the along-grain bars, but did not affect Q for the cross-grain bars.  Statistical analyses showed that all of the top coat finishes cured for seven weeks were equivalent with respect to their effect on the vibrational properties of the spruce bars. Cover Image

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Savart Journal

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  • Article published Nov 7, 2015.
  • This article has been accessed 8367 times since publication.