When engaged on an acoustic guitar, how will you decide what sort of end was initially used? And how will you greatest match it to finish the restore?

Q: I’m engaged on a Martin with a few cracks, which I fastened by including spruce splints. I want to contact up the skinny satin end. How do I decide whether it is polyurethane or lacquer, and what’s one of the simplest ways to proceed? 
—Antonio Rojas Flor

A: Congratulations—you could have found a door to an alternate universe. Sadly, it’s one filled with potential pitfalls and disappointments. Touchup work is a darkish artwork that may take a few years to grasp. As with all such refined ability units, I might encourage you first to learn as a lot as you possibly can, and to observe on some unimportant materials earlier than working in your Martin.

If you’re making an attempt to match the highest colour, I might suggest sealing the repairs with shellac first. Make sure you use dewaxed shellac, which is not going to trigger adhesion points with any subsequent end merchandise. A skinny coat is sufficient to seal the restore and permit colour layering, with out the stain bleeding deeply into the naked wooden of the splint. Use a fine-tip brush and masking tape to maintain the shellac off the encompassing end as a lot as potential.

I’ve had excellent outcomes utilizing artist brush pens for colour touchup—the Tombow model is my favourite. These are available in a really wide selection of wooden tones with a really high quality tip for precision work. The water base additionally means they are often finessed or eliminated, if mandatory, with a moist Q-Tip.

Martin has used many various end merchandise over time, so it’s laborious to know whether or not your guitar is lacquer or another extra trendy product. You’ll be able to check for lacquer by dabbing some acetone on an not easily seen space to see if the end softens. I’ve used the world beneath the tuning machines for this check up to now), however in my basic touchup work, I typically proceed the identical method for both end. Satin finishes get their texture from flattening brokers blended into the product, and solely look appropriate when they’re straight out of the spray gun—there is no such thing as a straightforward technique to buff or sand a end to a convincing satin texture. 

Thankfully, Mohawk Finishes makes a twig can lacquer referred to as Good Mix, which is accessible in a satin sheen that nearly completely matches the Martin end. Search for the Matte 19-23 Sheen or Satin 35-40 Sheen, relying on which you suppose higher describes the end in your guitar. The wizards who designed these spray cans have managed to make a product that matches the manufacturing facility end virtually completely, which is a minor miracle.

As I stated, touchup generally is a maddening train, however those that excel at it are among the many most spectacular craftspeople I do know. For an instance of the artwork at its absolute peak, lookup Iris Carr, the sensible violin repairperson. Her touchup work borders on magic, and exhibits what is feasible with endurance, dedication, and many years of expertise. Better of luck!