As we in the Northern Hemisphere plod into the Winter season, which is a slow gig time for many of us, it might do us well to look over our instruments and think of some of the small things we can do to maintain, improve, and protect our instruments.
control is one of the most important things we can be aware of at this
time of year, and we've got some tools to help with that. If you find
yourself thinking about buying one of those rubber thingies
to hang in your bass to keep up the humidity, I have them. A common
brand name for them is "Dampit" or "Humiditron" - they consist of a
perforated non-vinyl tube with a sponge material inside, with a disk on
the end. You soak it in water, squeeze out the excess, wipe it off, and
hang it inside your bass though an f-hole. Put the bass into a bag/case,
and natural evaporation transfers the moisture into the inside of the
bass. (Important: If your bass is out in the open, the moisture just
evaporates into the room, having very little effect on the bass).
But the question is... do you really need one? If you have a laminated (plywood) bass, no. Carved or hybrid (carved top), yes, or at least, maybe.
The concern really applies mainly to carved (and hybrid) basses, whose massive solid wood tops and backs can shrink or swell significantly when humidity drops or increases beyond the usual environment. I've been babysitting Bob's old carved Juzek bass, which is used to normal or average summer humidity here in Southern New Jersey. As winter comes and my forced air heat comes on, the mental alarm bell goes off. Indoor humidity drops like a rock, causing moisture to gradually leach out of the wood, causing that top or back to shrink -- that puts pressure on the whole structure. If I'm lucky (and the bass seams are glued properly), the thinner mix of hide glue at the seam lets loose and the bass "pops a seam" -- sort of an organic safety valve. The fix for that is usually a pretty inexpensive one. But it's still a hassle.
Laminated (plywood) basses were developed for this very reason. Their more stable woods don't move with the weather enough to be concerned, since they are not solid wood; so you don't expect them to crack under those circumstances. That said, extreme conditions -- and especially, rapid CHANGES between conditions -- aren't good for any instrument. Very high heat and humidity can affect the hide glue, causing seams to separate, and it is possible that extremely dry weather could affect the typically solid wood end-block, though it doesn't happen often.
These little hose doohickeys (Dampits, RDM Humiditrons, and generic versions) can be a mixed blessing. They are not necessarily a bad idea as an on-the-road precaution if the bass is out and about for a long while, but don't worry about taking your bass to a gig without one, it shouldn't be a problem over that short exposure - unless you're playing an outdoor gig at the Arctic Circle.
If you've got a carved or hybrid bass, my suggestion is to get a household humidifier at your local "X"-Mart or equivalent; preferably one with a built-in humidistat control. The worthwhile units use a digital control to automatically go on and off all by itself to maintain the setting. Spend the extra bucks and get a good one, keep it clean and it'll last several seasons.
All I need to do is remember to refill it, and their angry little flashing lights as well as a low humidity number reminds me. It's a great excuse to keep your bass safe in your bedroom, because you then can humidify it and your lungs at night and not wake up with that dry and scratchy throat on those brutal winter mornings.
We also have several tools for humidity and temperature monitoring - worth a look, to protect your investment. Now go forth and humidify! (IF you need to...)