Above are the test results for Amaco Velvet underglazes fired at cone 10 on porcelain bisque. I did put 3 coats of Amaco Sahara Zinc-Free Clear (HF-9) glaze on top. "Real orange" came out to be brighter than "bright orange". "Intense yellow" was more like amber yellow. Chartreuse was a lovely green but it appeared a bit runny. If you choose to use this color, make sure you put on more than 3 coats. All other colors came out even and opaque. You may find this table from Amaco helpful too for firings at cone 10.
Colors from left to right:
row 1 - electric blue, bright orange, chartreuse, and red
row 2 - real orange, intense yellow, white, and hunter green