Guitar Finishes: Are the Modern Poly Finishes Better?

July 30, 2019

Image credit: fvancini via Creative Commons license, some rights reserved.  



When it comes to guitar finishes, people can have strong opinions. Nitrocellulose lacquer is considered one of the best finishes for acoustic and electric guitars, but many guitars today, even very high-end guitars, are finished with either polyester or polyurethane, or  combination of both.  PRS, for example, uses polyester for their base coats and polyurethane for their top coats. 


Nitrocellulose lacquer is considered to be the benchmark finish for a number of reasons. First and foremost, it’s the most familiar to people. Vintage guitars were finished in nitrocellulose lacquer, because that was what was available. When polyester and polyurethane started becoming common in the early 1970’s, the quality of the finishes didn’t compare to nitrocellulose lacquer. Poly finishes were thick, they muffled the vibration of the instrument, and they tended to look cheap. As a result, poly finishes have had a hard time overcoming that stigma among guitar aficionados.  


Things are different today. Polyester and polyurethane finishes have improved dramatically, and many would argue they are as good or better than nitrocellulose lacquer when all the desired qualities of a guitar finish are taken into consideration. As a result, many guitar manufacturers, and even many boutique makers, are moving away from lacquer in favor of modern poly finishes.


Here are some basic differences between each type of finish. 


Nitrocellulose Lacquer: This is the benchmark finish. When a lacquer finish is well-applied and buffed, the results can be absolutely stunning. Is it any wonder that companies like Martin and Santa Cruz still rely on nitrocellulose lacquer for their guitars? Nitrocellulose lacquer is light, thin, and hard. It also has good acoustic properties, allowing the instrument to resonate freely. 


But there are some downsides. Nitrocellulose lacquer can be a little fragile. It’s prone to cracking and checking, especially if the guitar is subject to temperature extremes, like getting hot by being left in the car all day or being left out in the cold. For this reason, some guitar manufactures that use lacquer finishes won’t ship guitars during cold snaps. They don’t want their finishes checking during shipping. 


Age can also cause lacquer to check and crack. As the wood expands and contracts, the finish sometimes can’t cope, and it tends to crack. It’s not at all uncommon to see cracks in the finish on older guitars for this very reason. 


But lacquers’s fragility can also be a strength. Nitrocellulose lacquer is solvent-based. When the finish is applied, it dries by the evaporation of the solvent component. This means that the finish can be re-activate by using the appropriate solvent. Damage to a nitrocellulose lacquer finish can be repaired seamlessly, in most cases, because the new finish will “melt” into the old. If done properly, finish touchups done on lacquer finishes can be nearly invisible. 


Polyester and Polyurethane: Today’s poly finishes rival that of lacquer in almost every respect. They can be applied very thinly (thinner than even lacquer in some cases), they are hard and durable, and yet they retain enough flexibility to resist the checking and cracking that lacquer is so prone to. Sonically, modern poly finishes are considered by many to be equal to lacquer.


Poly finishes now rival lacquer for their ability to produce visually amazing finishes. Skeptical? Next time you’re at a guitar shop, check out the PRS guitars. Those amazing finishes are achieved with polyester and polyurethane. 


Poly finishes don’t dry through the evaporation of solvents. Instead, they cure through a chemical reaction (much like the way two-part epoxy cures). This means that they aren’t affected by solvents like lacquer is. As a result, poly finishes tend to be more robust than lacquer finishes, but they are consequently more difficult to repair. For example a crack in a poly finish can’t be seamlessly touched up as easily as lacquer can be.  


From a manufacturing standpoint, poly finishes can be produced much faster than lacquer finishes. Lacquer can take weeks to dry throughly enough to level sand and buff. Depending on the formulation of the finish and the techniques used, poly finishes can cure much faster than lacquer dries. Taylor Guitars, for example, use a UV light booth to cure their finishes nearly instantly.  


Lacquer might be the benchmark by which all other finishes are judged, but maybe it’s time for that to change. Maybe, just maybe, polyester and polyurethane should become the new standard. 


Here’s a short video detailing Taylor Guitar’s finishing process. 







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