Humidity Control for Pianos
Because pianos are mostly made of woods, there is one optimum humidity that can be said to be beneficial to pianos, which is between 40-50%.
It's important that the wood and glue joints not get too dry: for them a good humidity is desirable. On the other hand, for the metal parts, more than 50% humidity is not needed, otherwise they will tend to oxidize or rust, and action parts will often stick when the moisture in the air rises above a certain level. But the worst thing for wood or wire is to have sudden or severe humidity changes, which can cause soundboards to crack or split, or condensation to form inside the piano, usually on the strings. Humidity changes are often responsible for a host of other undesirables: White spots on piano finishes; the need for more frequent tunings, as strings go out of tune in response to the soundboard swelling and contracting; glue joints cracking and opening up, and cracks or splits in the finish, in the soundboard, pin block, lids, legs and/or other structural members.
Outdoor vs. Indoor climate
Most people worry about moving their piano to a different climate, but it's important to remember there are actually two types: outdoor and indoor. The place where people seem to run into the most problems with any kind of piano (whether targeted for a so-called U.S. climate or not), is when they fail to have any concept of extreme, or rapidly changing, humidity conditions inside their home. By this I mean that there are homes where the humidity was so high you could feel it: it felt damp and muggy, and the piano owner wondered why keys and action parts on the piano were sticking, and why the strings were covered with rust. On the other hand, if you run your furnace in the winter to the point where the humidity in your home drops to 10 or 20 %, then don't be surprised if you do get cracks in your soundboard, and/or your pin block starts doing funny things. No piano will survive conditions like these for long. Depending on how well your home is insulated, the indoor climate may be quite different from that outside. Try not to park your piano close to sources of direct sunlight, radiators, aquariums, bathtubs or showers, heating registers, etc.
How to keep an (electronic) eye on the piano
I encourage piano owners to keep an electronic humidity gauge on their instrument. (These gauges are pocket-size and run any where from around 24.99 for one from Canadian Tire to around 60.00 for a more exotic one made by Dampp-Chaser"!, which you can order from us or from your piano technician. Both are accurate enough to let you know what's happening to your piano.) This kind of gauge has a built-in memory that is very convenient: it will remember the highest and lowest humidity for you so you don't always have to be there watching it. A good humidity compromise, or ideal, is around 42%, according to those who make humidity control devices for pianos.
Should you worry about buying a used piano originally sold in Japan?
In a nutshell, there is no reason, really, to treat these so-called "grey market" or "tropical" pianos any differently than you would any other used piano purchase: Have the instrument checked out by a competent technician, who will look for the same kinds of problems he would with any used instrument; and make sure the dealer/seller provides a warranty (generally 2 to 5 years is standard for used grand pianos of this type, which is certainly long enough for your tuner or technician to ascertain whether there will be any problems.) In our experience, having worked with both so-called "gray market" pianos, and ones originally intended for U.S. consumption, over several years, in both arid and more humid regions , I have yet to see any significant problems with either type of piano any more than the other, or any of the major complications darkly hinted at or alluded to by those whose emphasis is on selling the new pianos. Since there were reportedly problems with some Japanese pianos when they were first shipped here in the early sixties (for more on this, see discussion on seasoning pianos for different climates), you might want to be extra careful about inspecting any piano made previous to 1970, whether initially intended for the U.S. or Japan. After having serviced and maintained many pre-1970 Yamahas and Kawais however, we have not personally seen any that were simply "falling apart," or that had any type of significant seasoning, warping, pin block, rim, or soundboard problems, for that matter, beyond what you would normally expect in any used piano that had received normal care and maintenance. (I suspect that any of these pianos that might have had problems of a more serious nature were probably ones that were subjected to some really severe humidity extremes, or otherwise abused; as stated above, no piano will hold up long under those conditions, regardless of how its wood is seasoned by the manufacturer.)
No matter what is said about climate, we are not going to play our pianos outside. Inside the house climates can and should be controlled but we at Pianohouse Burlington Inc. always recommend any purchaser to consider buying a Dampp-Chaser system! We sell them for uprights as well as for grand pianos!