CRCasey wrote:But when you have to go to a fractional wavelength of a absorption pattern of light don't you think that a size that small really is not that useful in fluids like this. That is not what we want to measure for. You can pick a standard and work with it. A Micron standard may be overkill for this.
I have no idea what you mean by this. The shortest wavelength of visible light is roughly 400 nanometers, about 1000X smaller than the diameter of espresso grinds (and 100X smaller than the fines).
The only thing that makes grid sizing confusing, is the contribution of the wires in the mesh. Otherwise it would just be the distance (e.g., one inch) divided by the number of openings (e.g., 30).