How Will Your Guitar Age/Relic Naturally
Discounting how people relic their guitar on purpose in this article I will be talking about how you can expect a guitar to age if you just leave it to do it by itself over time. Some people like the look of an aged guitar, some people don't, this is just personal opinion. My aim of this article is going to be about how different guitars can be expected to age, different parts made from different materials will age differently.
Each separate guitar will age differently, even if they are made next to each other at the factory. This is because all guitars are treated differently in the lifetimes, some are gigged hard and left out of their case, some are just played at home and kept protected. Even guitars that are just kept at home can age significantly differently depending on the climate they are kept in and the amount of sun/ UV the guitar receives.
Body Paint & Lacquer
Older guitars (Before mid 70's) and some more expensive modern models (and all USA Gibsons) have Nitrocellulose finishes. These nitro finishes age like you see on many famous old aged guitars and give the classic aged look. They yellow in colour and lose some of their deep shine by going slightly dull. This is because the nitro is always evaporating thus getting thinner, and has little UV resistance. Any dings on the guitar body over time will mainly show as cracks in the finished, as will any quick changes in heat causing cracks called "Checking".
Most modern or cheaper guitars are finished with Polyester or Polyurethane on top of the paint. This finish doesn't crack, or dull like nitro however it does yellow slightly over time due to UV. These guitars tend to chip if bashed sometimes to the point where an old poly guitar can look almost pebble dashed if not well looked after. This finish is much stronger than the previous nitro finishes.
Body finishes take years upon years to age, apart from knocks on the guitars (Which depends on how careless you are), to get any noticeable yellowing you will be waiting at least 10 years if the guitar is left out in the house, even longer if kept in its case.
Do you like the look of aged guitars?
Lots of guitar necks are made from maple, with age maple goes a slight yellow tint. This happens no matter what the finish of the neck is. Finish also effects necks, if your neck is nitrocellulose finished then the neck will darken over time easily as the nitro wears, and eventually you may wear through the finish. If the neck is poly finished then it will darken over time as it gets dirtier from your hands, and if the poly is thin then it may wear in the same way the nitro does (It will just take much longer.). If the neck finish is a "satin" finish then over time your hand will polish the back of the neck into a gloss finish.
If you have a satin finished neck it will wear to become shiny and gloss.
Plastics are often the most obvious sign of aging. It happens the quickest with the different often becoming noticeable within a couple of years. This aging is often obvious on Fender guitars or guitars with large pickguards, models such as the Stratocaster and Telecaster commonly have white pickguards when new. This acrylic plastic ages quickly when exposed to UV light. From what I have researched and obvserved it seems that Squier's tend to age quickly, my affinity series is showing significant yellowing after only a year (in a non smoking household). In comparison I have seen pictures of some American standards that don't seem to have aged at all in 5-10 years.
Interestingly the very first Fender Esquire's, Nocasters, Broadcasters and Stratocasters produced in the early to mid 50's used a "bakelite" plastic where the pickguards seem not to yellow, even in the 50-60 years since they were made.