Marbling
Float colour on size, draw it into veins, and pull a print
Pulled prints hang here to dry
Patterns
Watch one made from a fresh ground, then work into it yourself.
On the trough
Marbled paper is printed from colour floating on size, water thickened with seaweed. Each drop spreads into a thin film and shoulders every film already there out of its way, so the first colours thrown end up squeezed into veins between the last.
Nothing on this trough is painted pixel by pixel. Every film is an outline, and every drop and stroke is an exact transformation of the surface, after Aubrey Jaffer's mathematical marbling. A drop moves each point straight out from its centre just far enough to make room for its own area. A tine slides each point along its path, less the further the point lies from it. Outlines are cut finer as they stretch, so the veins stay sharp at any size, and a print can be saved as vectors.
Paper laid face down on the size comes up as the trough's mirror image, so your print reads the other way round.
Keys: 1 to 5 choose a tool, Z undoes, P lays paper, Esc stops a pattern.