Guitar Finishes are a hot topic among players, often sparking debates about tone, durability, and aesthetics. Walk into any guitar forum, and you’re bound to find discussions—sometimes heated—about whether a certain type of guitar finish is “better” than another. But what are these finishes actually made of, and what are the real differences between them? Let’s dive into the world of guitar finishes, specifically looking at nitrocellulose, polyurethane, and polyester, to clear up some of the myths and understand the facts.
First, let’s understand the basic types of finishes we’re discussing. We can broadly categorize them into solvent-based and reactive finishes.
Nitrocellulose lacquer is a classic example of a solvent-based finish. Think of it like this: imagine dissolving sugar in water. The sugar is suspended in the water. With nitrocellulose, the “sugar” is the solid material of the finish, and the “water” is the solvent. As the finish dries, the solvents evaporate, leaving behind a solid film on the guitar. Crucially, this film remains somewhat porous and can continue to lose solvents over time, leading to the aging and “checking” that many players find desirable in vintage instruments. Another characteristic is that nitrocellulose can be re-dissolved by solvents even after it’s cured, which has implications for repairs.
Alt text: Detailed view of a nitrocellulose guitar finish exhibiting subtle lacquer checking, a common aging characteristic.
On the other hand, polyurethane and polyester finishes are reactive finishes. These are fundamentally different because they cure through a chemical reaction, not just solvent evaporation. Think of epoxy resin. Reactive finishes involve two main components: a resin and a catalyst (hardener). When these are mixed, they undergo a chemical reaction where molecules link together, forming a robust polymer—essentially a type of plastic. This process is called cross-linking. The result is a very dense, non-porous film that’s highly resistant to liquids and solvents once fully cured. While reactive finishes do contain some solvents that evaporate during application, the key difference is that the cured finish cannot be re-dissolved.
Polyurethane and Polyester in Detail
The term “poly finish” is often thrown around in guitar circles as a general term, but it usually refers to either polyurethane or polyester. These finishes became popular for manufacturers due to their efficiency and durability.
Polyurethane finishes started gaining traction with Fender in the late 1960s. The shift was largely driven by cost and production efficiency. Polyurethane could be applied in fewer coats than traditional nitrocellulose lacquer, it dried faster, and it buffed to a high gloss with less effort. Furthermore, in a time when aged nitro finishes were often seen as undesirable flaws, polyurethane offered a finish that resisted yellowing and cracking. It also proved to be much more durable for working musicians, offering better resistance to scratches, wear, and spills of all sorts.
Alt text: Electric guitar, a Fender Stratocaster, showcasing a high-gloss polyurethane finish in a sunburst color.
Polyester finishes entered Fender’s production in the early 1970s, aiming to supersede polyurethane. Polyester is similar to polyurethane but typically has an even higher solids content. This characteristic meant it could build up to a substantial finish thickness even more quickly than polyurethane, further reducing application time and also reducing VOC emissions from solvents. Polyester finishes are exceptionally hard and durable, offering even greater protection to the wood. For manufacturers looking for speed and resilience, polyester seemed like the ultimate solution.
However, despite the practical advantages, these newer finishes weren’t universally embraced by guitar players.
A common complaint emerged: “My tone!” Many guitarists felt that guitars finished with these “plastic-like” coatings sounded inferior to older instruments with nitrocellulose finishes. The idea that thicker poly finishes choked the “breathing” and resonance of the wood became widespread. It was argued that guitars needed to breathe and resonate freely, and that the thick, impermeable poly finishes were stifling their tonal potential.
Alt text: Close up of a vintage electric guitar body showing the aged and slightly worn nitrocellulose finish, highlighting its classic appearance.
However, the impact of finish on tone is a complex and often debated subject. While some early poly finishes were indeed applied very thickly, it’s questionable whether the finish itself was the primary culprit in perceived tonal changes. It’s more likely that other cost-saving measures implemented around the same time, particularly changes in pickup components and wiring, had a more significant impact on the sound of these guitars. The shift to poly finishes coincided with broader changes in manufacturing processes, and attributing tonal changes solely to the finish might be an oversimplification.
Were thick poly finishes applied? Yes, sometimes. The transition to these new materials may not have always been smooth. Spray technicians accustomed to applying numerous thin coats of nitrocellulose might not have immediately adjusted their techniques for high-solids poly finishes, potentially resulting in thicker applications than necessary.
But are poly finishes inherently bad for tone? The answer, overwhelmingly, is no. Major manufacturers like Fender continue to use polyurethane and polyester finishes extensively on many guitars today, and these instruments are capable of producing excellent tone. Over time, application techniques have been refined to achieve thinner, more even coats. Across the guitar industry, poly finishes are used on instruments at all price points, and the quality of sound is determined by numerous factors far beyond just the type of finish.
Alt text: Image of a modern guitar production line, focusing on the spray booth where guitars are being coated with finish, demonstrating contemporary manufacturing processes.
While the myth of poly finishes “killing tone” persists, it largely exists as a form of accepted wisdom, a kind of folk memory in the guitar world. Many players appreciate the aged look and feel of checked nitrocellulose, but objectively, poly finishes are not tonally detrimental. In fact, many guitarists value the durability and pristine appearance that poly finishes offer, preferring their instruments to remain scratch-free and glossy for years. Poly finishes and other modern coatings cater to these preferences.
From a repair perspective, polyurethane and polyester finishes present their own challenges. Their very strength and chemical inertness, which are advantages for players and manufacturers, become drawbacks for repair technicians. The inability of new finish to chemically bond with cured poly means that repairs and touch-ups are more complicated. New finish essentially sits on top of the old, making seamless repairs difficult to achieve and often resulting in visible “witness lines.”
However, repairability is becoming less of a primary concern in modern mass manufacturing. The advantages of polyurethane and polyester in terms of durability, efficiency, and environmental impact mean they are likely to remain prevalent in guitar production for the foreseeable future.
In conclusion, well-applied poly finishes can result in stunningly beautiful guitars and do not demonstrably harm an instrument’s tone. While nitrocellulose holds a certain romantic appeal and ages beautifully, modern poly finishes offer a practical and tonally sound alternative. As new finish technologies continue to emerge, polyurethane and polyester remain vital and widely used options in the guitar world.
