Intense Black is classified as a transparent, but it looks pretty opaque in anything I have ever used it in. It is a super-saturated colour, and makes beautifully crisp black stringer design on top of every colour I've tried.
1 - Plain, 2 - Plain (reduced), 3 - w/ Silver Leaf, 4 - w/ Silver Leaf (reduced & encased), 5 - w/ Silver Glass Frit (reduced), 6 - w/ TerraNova2 Frit, 7 & 8 - w/ Tuxedo, Copper Green, Opal Yellow, Ivory, Peace
If you get Intense Black really, really hot after using a small amount of it on top of another colour, it will web like crazy. I intentionally did not do that thing in any of these test beads, to try to see if I could also get Intense Black to behave nicely and NOT spread around. As it turns out, without any particular skill or practice necessary, it is easy to control this aspect of Intense Black.
Silver sort of disperses and disappears on top of Intense Black, but when the silver is reduced and encased, you can see in the bead on the right that it forms a shiny, metallic silver layer under the clear.
Intense Black makes an unexpectedly good base for silver glass. My striking silver glass frit bloomed nicely, and the reduction frit looks pretty nice as well.
And here you can see how dark and crisp the intense black lines are over the other test colours. The bead on the left doesn't show any real reaction between colours.
In the bead on the left, the opposite seems to be true. Copper Green separates so that it is pink and crusty around the edges but then turquoise and 3-dimensional-looking in the centres.
Ivory separates and develops a fine line down the middle of lines and a fine dot in the middle of dots when it is used over Intense Black.
When Peace is used over Intense Black, the Intense Black bleeds into it, making it look murky.