Introduction

Choosing the right finish for an acrylic-painted guitar body is crucial to ensure both aesthetic appeal and protection against environmental factors. While spar urethane might seem like a viable option, it has significant limitations that make it less ideal for guitar finishes. This article delves into the specifics of spar urethane and polyurethane finishes, highlighting their benefits and shortcomings for guitar bodies.

The Use of Spar Urethane on Acrylic-Painted Guitar Bodies

Compatibility: Spar urethane is typically compatible with acrylic paints, but adhesion can be a concern. Since the surface has not been sanded, the paint may not adhere well. Sanding can improve adhesion, but if this is not an option, the paint must be fully cured to enhance surface quality.

Application: Apply the urethane using a clean brush or spray to prevent contaminants. Thin, even coats should be applied, allowing adequate drying time between each coat. The product instructions should be carefully followed to ensure optimal results.

Testing: Before applying the finish to the entire guitar body, test it on a small, inconspicuous area to ensure compatibility and to check for any adverse reactions. Signs of lifting, bubbling, or discoloration should be avoided.

Finish: Spar urethane can alter the appearance of the paint, potentially darkening it or giving it a glossy sheen. However, it is generally not the preferred choice for guitar finishes due to its satin nature and potential yellowing over time.

Durability: Spar urethane is designed for outdoor use and provides good protection against moisture and UV light, making it a feasible option. Despite this, it may not perform as well as clear polyurethane or lacquer finishes, which are more commonly used for guitar bodies.

Understanding Spar Urethane

Pliability: The term "spar" refers to the flexibility of the material, which is beneficial for outdoor items like wooden boat spars that expand and contract in various weather conditions. This pliability, however, leads to a less durable finish compared to traditional polyurethane, which offers a harder and more protective surface. This hardness is exactly what guitar finishes require to withstand playing and handling.

Color Change Over Time: Spar urethane tends to yellow with age, a characteristic that is generally undesirable for a guitar finish. This color change can detract from the visual appeal of the instrument over time.

Performance: While spar urethane can be applied to a guitar, it is unlikely to perform or look as good as a clear polyurethane or lacquer finish. These finishes are specifically designed to provide a protective layer while maintaining the clarity and aesthetics of the underlying paint.

Conclusion

When it comes to protecting an acrylic-painted guitar body, the choice of finish is crucial. Spar urethane, although compatible with acrylic paints, may not be the best option due to its pliability and potential yellowing over time. For optimal performance, a polyurethane or lacquer finish is recommended. Testing and proper application techniques are essential to achieve a high-quality finish that enhances both the appearance and durability of your guitar.