What materials are used to write black and white characters in hard-pen calligraphy works?

I usually copy my works into photos and send them to my computer. After image processing software, I turned the background into black and the handwriting into white, which was very simple. I guess what you said should have the same effect. I have never seen black paper for writing. If there is, it may be silver chalk, which is white when written, but it is easy to erase. Paper is probably black cardboard or something. Brush calligraphy or seal cutting works usually have the effect of rubbing white characters on a black background.