Yes you can make you own by adding barium sulfate to white paint, not as good as the expensive integrating sphere paint but pretty good for large white diffuse

Yes you can make you own by adding barium sulfate to white paint, not as good as the expensive integrating sphere paint but pretty good for large white diffuse panels on a budget. I watched as the rooftop out my window was painted white, it was extremely reflective. After a year, visibly the roof is dark gray. I wish I would have taken a daily picture and spectral measurement, maybe next time.