Many high-end guitar manufacturers finish their guitars in nitrocellulose finish/lacquer. Some musicians have discovered that over time, any type of rubber padded tuner that clips on to the headstock of the guitar can have a chemical reaction, resulting in the unwelcome breakdown of the nitrocellulose surface.
Some clip tuner manufactures state their product is "nitro-safe" but as there are many variants of nitrocellulose available, one guitar manufacturers' finish can differ greatly to another.
Another consideration is the possibility of the raw rubber of the clip being dual/triple sourced from multiple suppliers due to manufacturing availability, additional bonding chemicals used in the process, then add to this the age of the nitrocellulose and how much UV light it has/or will be exposed to - a 100% safety guarantee cannot be assumed by either the manufacturer or the user.
For this reason TC Electronic cannot guarantee the Polytune Clip, Polytune Clip Black or Unitune Clip will not have an adverse reaction on contact with any nitrocellulose finish.
Given the above information, if you still wish to use your tuner, it is advised that it is removed from the headstock when not in use.
For high-end guitar users who may have concerns, TC Electronic advise using one of our many robust and reliable foot pedal variants such as the Pollytune Mini or even a virtual tuner such as the Pollytune iPhone App.