These two abstract designs are done using an old credit card to scrape thickened turquoise and lemon dyes onto paper. The darker lines are made by using a heavily loaded card that leaves thick streaks. On paper, leaving white areas added texture and lightness, but didn't look so good when I tried it on cloth.
This next one has no white left. I have also added scribbles using a needle-nosed bottle. The thickened dye needs to be quite a bit runnier for this.