In a previous post, I outlined my method for measuring cane hardness. Although hardness and density are closely related (it makes sense that a hard piece of cane may be more dense compared to soft piece -- and my measurements mostly bear this out), I have found enough reason to measure both.
In this post, I'd like to describe my method and my findings for measuring cane density. I have been using this method in concert with measuring hardness for two years now. I feel I have amassed enough results to draw some solid conclusions from my efforts.
What I'm about to share with you is a way of selecting cane that has doubled my yield of good reeds made from blanks using this process.
Before this, I would average maybe 2 good reeds from 10 blanks. Pretty good, considering the standard I have to maintain given the musical crucible of The Cleveland Orchestra. Now I consistently get 4-5 out of 10!
First, I'd like to acknowledge the help I received in pursuing this idea from bassoonist, David Rachor and Jean-Marie Heinrich, a scientist who has devoted much of his research to the physics, botany and geometry of arundo donax (our cane).
Density is commonly measured in relation to water, which is given a value of 1. Thus, something less dense than water (all cane in a dry state) will measure between 0 and 1.
This is the equation used to determine the density of a substance.
A pycnometer is most commonly used in measuring density.
The density is measured by the amount of water displaced by a substance when it is immersed in a chamber filled with water. A more dense substance will displace a greater amount of water.
To determine the density of a piece of cane using this equation, you need a strictly constant volume of water and mass from trial to trial and piece of cane to piece of cane. Thus, the pieces of cane measured must be as close in mass to each other as possible (this would necessitate lots of minute trimming to the pieces of cane). Keeping a constant amount of water in a chamber while measuring many pieces of cane would probably prove too difficult for easy use. Just the act of taking a piece of wet cane out of the water when finished measuring would change the volume minutely, and, over time, skew the results a fair amount.
Measuring cane density this way is too fussy and time consuming.
The test I use does not directly measure the density of cane. What it measures is the specific gravity of a piece of cane and compares it with that of water.
I use a scale with a calibration of .01g. A tolerance this small is necessary to show the minute differences in density from piece to piece. A postal scale or a kitchen scale isn't accurate enough to detect differences in cane mass.
- First I weigh a dry piece of cane. It can be gouged, shaped, profiled, simply gouged or just a split piece of tube.
- I record the dry mass. (M1)
- Then I submerge the cane in a pan of water suspended over the scale by placing it under a rack that sits on the scale.
- I record the wet mass (M2) and remove the cane from the water. It spends just a few seconds in the water.
D= density, M1=dry mass, M2=wet mass
D = M1
What I'm measuring is could also be described as buoyancy or porosity. Cane that exerts more upward force under water against the rack than that which doesn't is more buoyant. I'm measuring the mass of a piece of cane in two different media -- air and water.
Since dry, aged cane is composed of cellulose fiber and lots of air spaces, it is reasonable to assume therefore, that cane with more air spaces per square millimeter will be correspondingly less dense than cane with fewer spaces.
This indirect way of measuring cane density takes about 20 seconds