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Construction - Finishing 1

Finishing

 

Once the binding is cleaned up, the instrument is ready for finishing.  Several coats of Shellac are sprayed on to seal the stain.  Initial coats may result in some bleeding of the color onto the binding, requiring additional clean up—not a large effort, just close inspection.

A note about dealing with the f-holes: I use a chop stick to push as many paper towels into the body cavity as it can readily accommodate.  When the finish is complete, the towels are removed using a pair of forceps.  Low-tech but effective.

As complex and confusing as the choice of coatings may be, it’s important to remember that every finish is nothing more than one type of resin or another dissolved in a solvent.  After the finish is applied, one of two things happens:

  1. The solvent evaporates, leaving behind the resins—Evaporative Finishes.  Spirit varnish, shellac, lacquer, and polyurethane are examples of evaporative finishes.

  2. As the solvent evaporates, the resin is chemically transformed—Reactive Finishes.  Oil varnish is probably the only example applicable to instrument building.  Tung oil, Danish oil, and epoxy coatings are other examples.

Regardless of the type of finish used, once all the science and mystery are cleared away, they all do the same thing.  They leave a thin coat of resins on the wood.

The choice of finish comes down to four criteria.

  1. Sound quality
  2. Appearance
  3. Durability
  4. Ease of application
Of course no single option offers the best choice for all criteria—compromises are required.  Not surprisingly, most luthiers consider sound quality the top priority, while production-line operations may lend more weight to ease of application and durability.