DIY Network

Handmade Mandolin, Part 11: Final Wood Finish From "Handmade Music" episode DHMM-107

	Lynn Dudenbostel applies the varnish by hand, using a brush rather than a spray booth.
	Lynn may apply as many as eight coats of varnish, but sands away much of that between coats.

Building a mandolin is a major undertaking but, at this point when the varnish is applied, the payoff becomes apparent. With a number of coats of stain and shellac applied and fully dry, the mandolin is now ready for the next step in the finishing process. In this segment, the varnish is applied and the finish is finalized using an old-school technique known as French polishing.

Materials:

Varnish
Paintbrushes
Rags
Sandpaper
Masking tape
Protective gloves

Safety Alert: When working with stains, varnishes, solvents and other toxic chemicals, work in a well-ventilated area. For some procedures, a ventilator mask is recommended.

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Wood Finish, Part 2: Varnish and French Polish

• Lynn applies the varnish using a brush (figures A and B) rather than a spray booth. It's still the best method of application. "In brushing the varnish," says Lynn, "I find that it takes anywhere from six to eight coats to accomplish a proper finish." But as Lynn is fond of saying, it's not how many coats are added to the instrument, it's how many are left.

  Figure A

  Figure B

  
  
  
• Although he might add as many as eight coats of varnish, it's important to note that he also sands away much of that between applications. "I'll let it set for 24 hours," he says, "then come back with 800-grit sandpaper and very lightly scuff that coat of varnish that I've put on." Following this technique he can achieve a remarkably smooth and attractive finish that's thin enough not to hamper the sound of the instrument.

  Lynn begins slowly, adding coats only as necessary. Each coat applied is followed by sanding. The initial between-coat sandings are dry, but for the later coats Lynn does wet-sanding using ultra-fine 1500-grit sandpaper (figure C and D).

  Figure C

  Figure D

  
  

  Figure E

  
  

• After wet sanding, depending on what the finish "tells" Lynn, there could be more coats of varnish applied (figure E), followed by more wet sanding. Ultimately he finishes with 1500-grit paper. A light touch is required for sanding since he never wants to sand through to bare wood. It's a balancing act, getting enough on to achieve a smooth, perfect surface, but not leavening any more on than is necessary so the acoustics aren't compromised. By the end of this ritual, the wood has taken on a beautiful luster.
  

  Figure F

• And after one more light-sanding Lynn's ready for the final finishing step -- French polishing. "To get a nice gloss back on the finish," says Lynn, "you French polish it [which is] little more than shellac, with a little bit of walnut oil as a lubricant, that's applied with a pad. This is the way the instrument in the '20s were done -- with an oil-based varnish with a spirit top-coat. It adds just a little bit of shellac to the top layer of varnish, bringing it to a nice shine." (figure F).
  

RESOURCES :

Kentucky Thunder
For more information on the band that appeared in DIY's Handmade Music, Kentucky Thunder -- and to hear streaming audio and download samples of their music -- visit the website for Skaggs Family Records, www.skaggsfamilyrecords.com.

Stewart MacDonald's Luthier Supply Shop
Website: www.stewmac.com

Luthier's Mercantile International, Inc.
Website: www.lmii.com

Pioneer Valley Luthier Supply Company
Website: www.pioneervalleyluthier.com

GUESTS :

Lynn Dudenbostel, Luthier
Dudenbostel Stringed Instruments
Knoxville, TN