just wanted to say thanks to you all for the rich discussion on this
Chris
Timothy Motz wrote:
Thank you Dana. That was my point exactly and you explained it better
than I did.
I've worked in art museums for 25 years, where we are very concerned
with temperature and humidity for reasons similar to those of
luthiers. The ideal is about 68 degrees Farenheit and about 55
percent relative humidity, with minimal variation. Should a gallery
have problems with dropping humidity, the easiest way to fix that is
to drop the temperature a bit. But these days with modern computer
controlled HVAC systems that hardly every happens. I keep one of my
first lutes in the office to practice on during my lunch hour, and it
rarely goes out of tune as a result, even with gut strings.
One thing that DvE and Spanish guitar builders don't deal with as much
as American builders is excessively high indoor temperatures (above 72
degrees Farenheit) with resulting extremely low relative humidity,
close to that of desert conditions. Even with a humidifier on my
furnace and the temperature kept at 68 degrees, I get nosebleeds at
home from the dry air and have to use saline sprays. So when I say I
assemble instruments in the winter, that's the extreme
temperature/humidity conditions I'm attempting to compensate for. I
lived in Italy for a short time, and I do remember that they didn't
keep their indoor temperatures at NEARLY what I was used to. Lots of
sweaters. So the seasonal changes in humidity might be less drastic.
I appreciated Richard's explanation of what happens during the
compression of a soundboard due to swelling. I had never stopped to
consider it's effects on the wood fibers.
Tim
On Feb 11, 2009, at 8:30 PM, <dem...@suffolk.lib.ny.us> wrote:
On Wed, Feb 11, 2009, rel...@sbcglobal.net said:
where I disagree with one of the posts ( If I read it correctly )
is that I
believe that generally humidity goes DOWN with cold and UP with
warmer air -
Perhaps you are confusing what happens in experiemnets with observations
of steady-states.
Consider a large room, sufficiently sealed that we can experiment inside
it.
The amount of water vapor can be considered constant (well, it increases
as the humans inside breath out moist air, make the room large enuogh
and
that can be neglected). If the air of the room is cooled, the
capacity of
the air to hold it decreases, and the relative humidity increases;
cool it
enough and you can make it rain inside the room.
Stabilise the room as to both temperature and moisture content, with
some
pieces of wood present (they too are stabilized). Raise the temperature
in the room and the air will have a greater capacity to hold moisture.
The moisture in the wood will migrate to the air until the relative
humiditys stabilize again.
Central heating systems using forced hot air take in cold air from the
outside, lower its RH by heating it, and dry out all the wood in the
house
(and the people) in the process. Sometimes there is a humidifier that
adds water vapor to the hot air, more comomonly not. Arctic air is
often
pretty dry to begin with, making this the dryest of the seasons for most
of us.
they only did their glue ups on tops during the later part of the
summer
when they knew the humidity to be around 5 or so percent LOWER than the
typical humidity in which the instruments were to live.
yes, very important. Some will have climate control in their shops, but
not all can do that; historically one worked on various tasks as the
seasons allowed.
--
Dana Emery
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