Black paint is easy to make and hard to make well, and the differences between the blacks were significant enough that painters specified which one they wanted.
Most blacks are carbon. Lamp black is soot collected from a burning oil lamp, fine and intense and slightly blue in tone. Vine black and other charcoal blacks are burnt plant material, coarser and cooler. Bone black or ivory black is charred animal bone, warmer and denser, and it is the deepest of the traditional blacks. A workshop with all three had a range of blacks in the way it had a range of reds.
Writing needed something different. Iron gall ink, the standard ink of Europe for well over a thousand years, is not a carbon suspension at all but a chemical reaction: tannins from oak galls combine with iron sulphate to form a compound that bonds into the parchment or paper rather than sitting on it. That is why it cannot simply be scraped off, and also why it slowly eats through the page, which is a major conservation problem for medieval manuscripts.
Black cloth was the real difficulty. A genuinely deep, non-fading black dye was expensive and technically demanding, requiring repeated dyeing and iron or tannin mordants that weakened the fibre. Cheap black cloth went brown or green with wear. The sober black of Burgundian and later Spanish court dress was therefore a display of wealth rather than of austerity, which reverses the reading it usually receives.