[13] “Item A new mode to make substantie ink. Take walnut husks and let them dry for 2 or three days and pound them in a stone mortar and put that in a cauldron and let it melt. Then strain it through a linen cloth and put it into a pot or a bladder. That is the substantie. Take an amount of this with wine or vinegar and water and let it get warm so that it dissolves. This is going to be good.” In: Kölner Musterbuch. 1490. Köln, Historisches Archiv der Stadt, Best. 7010 (Wallraf) 293: fol. 4v