Relative humidity

[LazyRiver]

Now that the dry season is approaching - at least where I live - I'm wondering about keeping my fretted instruments from getting too dry. I have a hygrometer, which gives me relative humidity and temperature in the room where its placed. As we know, relative humidity is just that - it's relative. Warmer air holds more water than colder air. So the RH varies in different parts of the house according to temp, being higher in the cold rooms and lower in the warm rooms. My question: is it better to put the instruments in a room where the temp is low - say 60 deg F or in a room where it is high - say 73 deg F. I suspect it doesn't make any difference,

[sunburst]

Moderate (like 60 to 73 degree) temperature differences don't make much difference to the instrument, other than the fact that, as you mentioned, RH is influenced by temperature. If you have a choice in where you keep your instruments, they will "feel best" at 40 to 50% RH, regardless of the temperature.
Some finishes can be damaged by temperatures around 40 degrees F while others are fine to temperatures much lower than that, so if the RH is good, temperatures much cooler than 60 are fine. Some glues and adhesives can be compromised at much lower temperatures than others, but if the RH is good, temperatures up to around 90 (and above) degrees don't generally cause structural damage, but some finishes can suffer in excess heat. Going from 90 to 40 degrees quickly is not a good idea because finish damage can easily result from the rapid shrinkage of the finish even if the RH is good in both places.

Bottom line, the temperature range you are talking bout is nothing to be concerned about as long as the RH is good.

[allenhopkins]

As John states, temperatures within the range of normal household temps very seldom cause damage. Sudden changes from below-freezing to "room temperature" can cause finish cracking -- ask one who knows...

My normal practice is to keep all my instruments (in their cases) in a basement room, which doesn't get as much direct heat as the rooms on the first floor, and where the ambient humidity tends to be the highest. What dries out "winter air" inside the house is heating it, which, as you correctly point out, drives down the relative humidity.

If you have an accurate hygrometer, and monitor it frequently, you can determine when to use in-case humidification, or room humidification, to protect your instruments. The difference in relative humidity between a room at 60º F, and a room at 72º F, shouldn't be enough to cause any change in an instrument. You can check this assumption by locating your hygrometer first in one room, then the other, and checking the readings.

[kurth83]

Yeah, its RH that matters, not temp, I prefer warmer rooms because my fingers aren't as stiff. :-)

Wood absorbs moisture from the air based on RH (and swells or shrinks based on moisture content). I found a table on moisture content vs RH once for wood at a lumber company's website. It showed that only RH mattered, moisture content was independent of temperature. This held true from freezing up to 100 degrees F, with slightly higher RH (10%) needed at 120 degrees where the table stopped.

I think other things on the instrument (like glues and finishes) will start to go bad at extreme temperatures before the wood will suffer harm as long as RH is maintained and no sudden changes are made.

It may be true that in your house RH is lower in warmer rooms than cooler ones, but in the end RH is what is important.