What are the components involved in moisture control?

The components are:

  1. Blowstick and water trap (consisting of an elbow and a tube)

     Moisture traps deal mostly with spit.  The first thing they do is divert the spit away from the chanter reed toward the back of the instrument.  This is usually done with an elbow a tube.  If your trap has an elbow, then the larger water/spit particles will be knocked out because they aren't carried along in the flowing stream of air.  The medium sized "bits o' spit" will fall out of the airstream and collect in the tube.  This is an aerodynamic issue in which particles obey "stoke's law".  This law says that big particles fall faster in a viscous fluid and that small particles will remain suspended longer.  The slower the fluid is moving, the more efficiently the particles are removed.  This is best done in a large diameter, long tube so that the air is moving slowly and you catch most of the particles that fall out.  There are obvious practical there are practical limitations.  In particular, very small particles of water will remain suspended for a long time and will go through the trap.

    What exits the trap will be very humid air with very fine particulates of spit.

    (Note: In case you were wondering, all humans (and most other mammals) have the same humidity of air coming out of our lungs, it's the spit level that's different.  Pipers will refer to themselves as wet or dry blowers.  This a roundabout reference to the amount of spit in their air stream.) (Note #2: The restriction that these components add to air-flow can be calculated based on the physics of fluid flow and I intend to do so, someday!)

  2. Low temperature surfaces

    The moisture that gets through the water trap will be at about 100% RH at about 90 F and will have some spit in it.  As it flows through the back of the bag, it will contact the cooler surfaces there and will condense.  Absorption of this condensate is one purpose of "seasoning" in hide bags.  As liquid water becomes present in the bag, the relative humidity in the bag will be 100% at whatever the temperature of the bag is (i.e., somewhere between 90F and ambient).  It is important to note that contact time with the walls of the bag is probably pretty limited, so this isn't very efficient.
  3. Desiccant/absorbent

    Desiccants and absorbents are materials which have the ability to attract moisture from the air.  If desiccant is dry, has a high surface area and the flow rate is slow, the relative humidity of the air can be significantly reduced before it reaches the reeds.   

Desiccants do have limitations in that the humidity of the air passing over the desiccant will increase as the desiccant becomes more and more laden with moisture.  Hence, you should use "dried" desiccant on those cold damp days when you know you need it.  The ability of a desiccant to absorb moisture is also a function of temperature.

Copyright S.K. MacLeod 1996-2016