Did you take a photo paulstung?
What has happened to coolants/tubing? My last custom loop I used black coolant with clear masterkleer tubing. When I finally tore it down to sell well over a year later there was no platiciser, build-up or barely any staining.
Seems like there has been steps backwards...
I'm looking at Mayhems UV black instead. even properly diluted etc the pastel still is stronger. Thanks for the suggestions, I'll look at those as wellIf i remember, Feser and EK do black coolant.. not sure about staining, but have used various other colours from their range with no problems to tubing (clearflex, masterkleer, tygon as examples) or blocks