Finish around binding changing?

[Mandolusional]

Hi everyone, I have a question I hope some of you builders can help me with. I have a hand made varnished F5 that was finished in 2009, and today after playing I noticed a small "seam" has appeared along the side of the binding. I don't do a detailed inspection of the binding on a regular basis so I'm not sure if this has been there a long time or if it's growing or not. I tried to take a picture, but it is impossible for me to capture using my camera.

It is not a crack or a full blown seam (yet or ever I hope!), it almost appears as though the varnish is shrinking up ever so slightly along the binding. There is no wood exposure, and as I mentioned it's not a crack, but I can see a sort of line forming there. I know that may not be a very good description but for the life of me I couldn't get a photo of it.

I'm not one to "baby" it too much, but of course I also don't want to be negligent and thought I should ask. I currently live in a four season area, so I am just afraid it has to do with dryness and humidity (I humidify or dehumidify the room depending on season) and is something I need to be worried about, or if it is just somewhat natural as varnish ages.

Sorry for the long winded question and lack of a photo, but any insight would be great, thanks!

[Big Joe]

It sounds like lacquer sinking. This is a normal process and how much it sinks is dependent upon the kind of finish, how thick it is applied, how wide the gap between the binding and the wood is, and how warm the instrument gets. It is not unusual to see this on instruments. Without seeing your instrument it is hard to know if anything else is going on, but finish sinking is not rare by any means.
Just make sure it is not a seam coming loose rather than just finish sinking. If it is a loose seam that needs to be fixed. If it is finish sinking then it is fine.

[sunburst]

You didn't mention whether the binding is plastic, but I'm assuming that it is. Plastic bindings usually shrink because of the evaporation of solvents used in it's manufacture and installation as well as solvents from finishes. Even if the binding is left in place for a long time to allow it to shrink before the instrument is finished, wood and plastic move differently in response to temperature and relative humidity. If what you are seeing is simply a 'discontinuity' at the edge of the binding, a little line where the reflection of light changes, it is perfectly normal. If there is any actual separation of the binding from the wood it should probably be evaluated by a luthier.

If the binding is wood, binding shrinkage is less likely but it can still happen if the wood of the binding and the wood of the instrument were not of similar moisture content when the binding was installed, or if the woods are very dissimilar in stability, but different pieces of wood move differently so again, if it is just a slight discontinuity it is normal.

[Mandolusional]

Wow thanks for the responses! John, it is indeed plastic binding. From my inspection I suspect it is either the finish sinking as Big Joe suggests, and/or the binding shrinking. My primarily concern was if it sounded like a somewhat normal change in the area around the binding or not. Since I do not really have access to any other mandolins it's difficult for me to compare. However your responses have eased my mind a bit. If it seems to change or I see actual separation I'll see about getting it looked at. Thanks again for the quick responses, I really appreciate it.