Magic Number 17
Since this is a boring (but important) topic, I’ll try to make this as concise as possible. Last season, I tracked the hardness of all 441 reeds I clipped.
The readings ranged from 8 (hardest) to 23 (softest). (Note that the higher the number, the softer the cane.) The results were simple: I had no success with any piece of cane that read 17 or higher. On the other hand, even the hardest pieces of cane occasionally worked.
Every hardness tester is different—the same piece of cane will yield different readings on different machines. However, I have noticed that the range from high to low numbers (15, or 23 minus 8) stays remarkably consistent from machine to machine, and the relative “point of no return” (about nine above the low, or “hardest,” number) also stays relatively consistent.
In other words, your machine might measure readings from 14 to 29 (which has a range of 15), in which case the point of no return would be 23. Each machine has to be tested, but they all seem to roughly fall into the “framework” outlined above.
There we go—as painless as I could make it. The experiment was absolutely worthwhile, since now I can throw away around 20% of my cane after testing.
Please feel free to ask questions in the comments—I intentionally simplified both the experiment and the results for readability.