Hi,  John Tuttle asked about protecting a piano from extremes of
humidity and mentions that the high temperature (80 degrees) is needed
for an elderly person living in the home.  Okay, I'll buy the high
temperature, but I certainly cannot buy the wide fluctuation of
humidity.

While a sealant will slow the absorption and release of moisture from
the wood, time will eventually take its toll.  You would have to coat
the whole piano, including the insides of everything.  That's just not
practical or even possible.

But let's go a step further.  The same problem exists for the elderly
resident.  Excess humidity makes the effect of summer heat on the body
much worse.  It also encourages the growth of mold.  Neither is good
for the resident.  In the winter, extremely low humidity is a disaster
for the lungs and skin of the elderly resident.  Do you treat the piano
better than its owner?

If the home has forced air heating, both problems are fairly easy to
solve.  If not, a portable humidifier and dehumidifier can make the RH
more nearly stable over the year.  Both will require attention by the
resident.  Another approach is to put the piano in an unheated room and
close the door and heat vents.  This will make for a more nearly stable
RH as the level of humidity will track the temperature.

We have both a humidifier and a dehumidifier in the furnace so the RH
stays around 50% all year long.  With the recent cold weather, we water
the plants more often and take more showers.  In the summer, we run
the air conditioner when it gets humid (and occasionally when it just
gets hot -- hey, I paid for it!).   Okay, hot usually equals humid
around here so both the pianos and the people benefit. We also have
a relative humidity meter where I can see it easily and I make sure
the RH doesn't go too high or too low.

Lastly, in the winter, we keep a wine glass full of water in one of
our piano machines.  The water lasts for several weeks so it keeps the
machine a little more humid than the house since the house gets down
into the mid-40s in really cold weather.  Note that the surface of the
water is small so the rate of evaporation is relatively slow.

Do the guy a favor and tell him to take care of his health, and the
piano will be healthy too.

Regards
Craig Smith