Titanium dioxide is the most common white pigment in paint, sunscreen, and even food products. It’s cheap, safe, and almost unsurpassed in whiteness. It’s also the baseline for calculating an optical property called screen gain, which is the amount of light reflected from a projection surface divided by the amount of light reflected from a titanium dioxide reference surface. Since titanium dioxide is the pigment used in most white paint, a smooth wall painted flat white has a screen gain very close to 1.
But you can do better. This method applies a high-gain optical projection surface using common, cheap materials — flat white latex paint and glass sandblasting beads. I started out trying to directly mix them (which doesn’t work) and happened on this “sprinkling” method by accident. It gives a much brighter screen surface than paint alone.