OK...So, from what you're saying...
The 2 scales represent measurements of completely different things & they should not be used on the same instruments.
When explained in that manner, it actually almost makes sense.
But, why are we ever trying to use a refractometer to measure gravity of any kind, when really it can't truly provide us with that data, based on the refraction of light?
Is Brix a unit of measurement that is based on refraction, or is it a unit of measurement that is based on density?
I was under the impression that it was to measure liquid density of sucrose solutions.
I can somewhat agree that (with beer/wort) the refraction vs. gravity probably cannot be measured in this manner.
But, I have a hard time believing that you can predict the density of sucrose in a solution using a refractometer, yet not be able to use that same instrument to extrapolate Specific Gravity, with as much accuracy.
I don't mean to start any arguments...I really want to learn & understand this.