Nitrocellulose lacquer naturally ages over time, giving the guitar a yellowish, antique quality, often with accompanying spider cracks, also known as crazing. Many players desire this road-worn look, and finishes such as water-based lacquers and polyurethane finishes do not age like nitrocellulose lacquers. A natural ageing process may take years to achieve if the guitar is stashed in its case for long periods. However, ageing may be achieved in considerably less time, all while the guitar is not being played. A minimal amount of tending to the guitar is required, and the effect is gradual.
Expose the guitar to sunlight. Exposure to ultraviolet rays is how nitrocellulose lacquer ages. Place the guitar into the light. If the sunlight is direct, do not allow the guitar to get hot. If the guitar is very warm to the touch, move it back, or into indirect sunlight. A guitar that gets too warm may cause the wood to warp. Indirect sunlight works just as well, and poses no danger to the guitar.
Use fluorescent lighting to age the nitrocellulose lacquer finish. UVB 313-fluorescent lighting can be used when sunlight is not available. Expose the guitar to the lighting, which quickens ageing.
Rotate the guitar. As the guitar sits in the sunlight, or fluorescent lighting, expose it evenly to the light source. While the guitar rests on a guitar stand, turn it every few days to ensure an even ageing process.
Guitar lacquer clear coats can be refinished with an amber-tinted clear coat, which instantly gives your guitar an antique look. They can be applied with minimal stripping and sanding. Normally, only a light sanding of the existing clear coat is required (See Resources 2 and 3).