It behaves like a good quality 140lb watercolor paper. So in theory, you can use water.
However, as one can imagine, transparent color doesn’t fire well on black paper. You need a lot of pigment for a color to show, and the colors still dry lighter. So you can’t really use a lot of water.
Like any type of black paper, how you deal with value on it is quite counterintuitive.
In the first painting I used mostly watercolor and mixed in some gouache white in the highlight area. The second painting is gouache. I personally like the the gouache one better.
I feel like I am very lack of imagination with this paper. For the second painting, I believe I could achieve similar effect with ink resist method. While using black paper makes it easier in certain ways, ink resist could have some unexpected result. In other words, it is not particularly empowering.
It could be just I don’t know how to make the most out of it.
The second painting is done on the back of an old painting (of a broccoli). When I soak the gouache painting in ink, I got some unintended texture. It’s probably because of the unevenness of the paper. I might have done some lifting or scrubbing for the old painting. I decided it didn’t hurt.
In general it’s fun to think about how many ways you can deal with a subject.
Now a few more words about old paintings. Good watercolor papers are expensive, so I never throw away old paintings, no matter how ugly they are. There are always ways to reuse them:
The obvious one is to paint on the back. If the paper is not flat, you can soak it in water, then lay it flat and add some weight on it (or re-stretch it). Sometimes the texture of the paper on the back is different. It’s still workable.
Another way is to examine the old painting and see if there are some elements can be used. The flames in the second painting was modeled after the leaves of the broccoli on the other side. Look at it upside down, side ways, hold it up against strong light, you may discover something different.
You can also directly use it. Tear it apart and make it into a new collage.
Take a picture of it and manipulate it into a new digital art with Photoshop, Procreate, etc.
These methods are not exclusive, and that one piece of paper can generate many artworks!