Klarinet Archive - Posting 000204.txt from 1997/02

From: Mark Charette <charette@-----.com>
Subj: Keeping a clarinet warm
Date: Fri, 7 Feb 1997 19:09:56 -0500

I've been lightly chided for a very frivolous answer to a very
serious question, and rightly so. So, as penance, I will relate a
little bit of my material properties background to the subject, but
without the math (because I don't have all the gross properties
for grenadilla in my CRC handbook ;^)

Materials crack or split for various reasons, but all have to do
with the release of internally stored energy. A crack wants to
start at some defect in the material because it's an area where
the energy can easily be dissipated, and the crack spreads because
there is more energy "behind" it trying to get out.

All materials have some sort of "glue" which hopefully is stronger
than the energy trying to split it. In wood, the fibers are interlocked
and hopefully the defects are few, along with the wood being in a
"relaxed" state.

Cold weather, however, changes two things dramtically. One is the
relative humidity. Wood is not dimensionally stable with varying
humidity levels, and heating a home changes humidity levels drastically.
As the wood shrinks, internal stresses build, and make it more likely
that the wood will get rid of it's stored energy along some defect.

The other, of course, is the temperature change. Wood is not
dimensionally stable as regards temperature, either. Add to that
the changes brought about with unequal heating (when you start playing
the instrument) and you have the receipe for disaster.

How to avoid the problem? One obvious way (which I have no empirical
evidence for) would be to seal the wood, using whatever bore oil your
tech recommends (I don't know what's best, but there are some
recommendations on the sneezy pages). The oil polymerizes in the pores
of the wood to create flexible plugs - the wood can expand and contract
due to temperature changes, but the internal humidity levels (internal
to the wood) should stay more constant).

Another obvious way is to keep the clarinet from expanding and
contracting too quickly. Taking it out and throwing it into the
trunk of a car in the winter is not going to be a good idea, along
with sticking it by the heater vent! A good, solid case with a
reasonable amount of foam surrounding the instrument would
theoretically be a "good thing". Wrapping it in aluminum foil will
also make a large difference (shiny side in or out? - I've done
experiments both ways with my kids, and there is negligable
difference either way, and whether you're keeping something hot or
cold). The aluminum foil thing during experimentation added about
20% efficiency (in temperature differentials after 2 hours) to 1" of
expanded close-celled polystyrene foam. We tested foil next to the
object as well as foam next to object - the results were statistically
insignificant.

The last thing - don't ever blow into a cold clarinet! The clarinet
may be 60 F., your breath 95F., and the 35F differential can split
the wood with NO problem at all!
--
Mark Charette Webmaster, http://sneezy.mika.com and maintainer of
Mika Systems, Inc the Clarinet Info Pages,
charette@-----.com/clarinet