mixing inks

wow. my first time mixing ink took a lot longer than i expected (about one hour)! i used the rubber-based inks instead of the oil-based because i have a lot of type but not a large amount of surface area to cover. i picked a pretty dark grayish-purple and the formula called for about:
     6 parts rubine red
     4 parts green
     1 part black
however, i think i started out with too much black! i ended up adding so much extra opaque white just to lighten it up a tiny bit. the color i was going for is close to the smeared out part in the picture above, but what it looks like on paper is the big glob part....basically black. as much as i tried to lighten it up, it still wasn't the purple i was going for.
note for next time: start with NO black and just add a little at a time.