My cork tester, sitting on a piece of cast iron.
Back when I got Black 3.0, I painted most of the cork a single layer, just to see how it did. When the 4.0 showed up, I painted the other end…demonstrably darker.
ETA: I’ve not done multi-layer of either type…I keep meaning to break it out for Nerf blaster painting [grips only; never BlackOut a blaster]. I’ve also considered having someone professionally use it to paint the blower scoop on my drag car (then seal with matte ceramic coating) and use some of Semple’s glow powders to line the INSIDE of the scoop to make a kind of star tunnel effect.
