When I first calibrated it and used it the coolant in my machine tanks was basically off scale or at the very top. I have refilled two machines with JUST distilled water twice, and they are just now getting down to about where they should be.
I was wasting a lot of money on coolant chemicals. I had assumed a lot of it was getting carried out with chips and spray out the top of the enclosures. In reality, that did happen, but nowhere near as much as I thought. By far the major has to have been lost as evaporation. I just assumed it was sprayed out and carried out because the coolant loss was so fast when cutting. No evaporation must have been so much higher due to increased surface areas due to splash and spray while cutting. maybe a little from "steam" at the cut as well.
I actually have not added any coolant chemicals to the coolant tanks ont he CNC machines since I received the refractometer. I did add a little at the lathe but not very much. All the water had evaporated, but the chemicals were still in the bottom of the tank.
Now, that often I may just be adding water with little or no chemical I will use flood much more often on the lathe, and maybe even on the big manual mill.
Slowly, against my will I am being dragged kicking and screaming into real machine shop processes instead of hobby hack operations.