Guitar relicing makes new guitars look old and worn, and checking is when the instrument's clear lacquer coat cracks. Checking develops naturally on nitrocellulose lacquer finishes over a tough rock 'n' roll history, and although it takes years, the process can be artificially accelerated. If you want your guitar to look like a gem from the 1960s, this process just may be what you're looking for.
Spray the circuit freeze or canned air, onto a small test spot on the back of the guitar, holding the can roughly 8 inches from the surface of the guitar. If using canned air, hold the can upside down while spraying. If you don't like the results, it is hidden on the back. Since these compounds achieve very cold temperatures, they essentially freeze the guitar's lacquer finish, causing it to compress and check (crack). Canned air is a product used to dust electronics, while circuit freeze is used on circuits to locate thermal components and cold-solder joints.
Apply the circuit freeze or canned air onto the guitar body, beginning with the back of the guitar, then the sides. Save the front for last Do one section at a time and do not spray the back of the guitar neck, as it will change its feel, and may not play to your liking.
Wait a few seconds for the spray to dissipate. When the spray is gone, the results are immediately seen. Wipe down the spray area and determine if the amount of checking is sufficient. If more checking is desired, repeat the process.
If trying to achieve checking when refinishing the guitar yourself, the lacquer must be allowed to completely set, which may take up to a month, depending on the number of coats. An alternative method is to set the guitar in a cold car overnight. If you live in a cold wintertime climate, put the guitar in a car, then heat it rapidly the next day, in front of a space heater or blow dryer.
Be sure to wear rubber gloves when spraying canned air or circuit freeze. Be aware this process does not work on polyurethane finishes.