Mezzotint works backwards from every other print process. The plate starts fully rocked, covered in thousands of tiny burrs that hold ink across the entire surface, and the image is made by removing that texture. Scrape and polish an area and it stops taking ink. Leave it alone and it prints black.
Rocked, not screened
That inversion is why mezzotint produces blacks nothing else in printmaking matches. There is no white paper showing through a screen and no line spacing to fill; there is only a metal surface holding as much ink as it physically can.
It is also why the texture is irregular. A rocker is walked across the plate at many angles by hand, so the pits never form a grid. The tool reproduces that with layered value noise at three scales rather than a repeating pattern, which is the difference between a mezzotint and a coarse halftone.
Rocking Grain
Grain sets the pit size as a percentage of the shorter image side, so a 1200px preview and a 4000px download carry the same visible density instead of the download looking finer.
Below 10% the pits approach single pixels and the result reads as film grain. Between 18% and 35% the texture is visible without dissolving the subject. Above 60% individual pits become shapes in their own right, which suits a poster crop and destroys a portrait.
Bite
Bite controls how sharply a pit switches between holding ink and staying clean. Low values give each pit a soft shoulder, so the plate reads closer to a continuous-tone photograph. High values force a hard decision and the output becomes a two-colour field of pits, closer to a rough aquatint.
Burnish and Ink Weight
These two do different jobs and are easy to confuse. Burnish compresses the tonal range from the highlight end, mimicking a scraper working the plate flat. Ink Weight shifts the whole range up or down before any of that happens.
Reach for Burnish when the highlights are muddy and Ink Weight when the entire image is too heavy or too pale.
Plate Colour
Traditional mezzotint is one plate and one ink. The Plate Colour slider is a departure from that: at anything above 0% it keeps a fraction of the source hue inside the inked pits, which stands in for the four-plate colour mezzotints made by rocking and inking a separate plate per channel.
Keep it under 40% if the result should still read as a print rather than a textured photograph.
Limits
The effect works from luminance alone. Two colours of equal brightness land on the same pit density no matter how far apart their hues are, so a red mark on a green field disappears. Separate them upstream with a channel mixer or a black and white conversion, then rock the plate.