Hu-Friedy's It's About Time | Assessing Instrument Sharpness

The condition of the instrument blade should be evaluated both before and after sharpening. Before sharpening, the blade should be evaluated to determine the extent of dullness. Some instruments may require a light sharpening while others may need more reshaping and reconditioning.
After sharpening it is vital to evaluate whether the sharpening objectives have been accomplished.
Two methods are available to determine the condition of the instrument blade:
The visual inspection or glare test; and
The plastic test stick.