This post is about putting ink on thread. I usually paint pigment ink (Tsukineko inks....www.jukeboxquilts.com) on cotton quilt fabric. Theses inks are marketed as permanent on natural fibers when heat set. I know that to be true from experience. What I have also heard said is that these inks are not 'fond' of man made fabrics like polyester. I've never played with ink and polyester fabric but I do use polyester thread so I thought I would experiment to see what happens when poly thread is inked.
I have been known to ink atop thread already quilted into a piece. Since I don't ever intend to wash my quilts (maybe vacumn),I've not worried about it... but today I thought I'd do an experiment. Below you see 4 fan-like threaded areas. Leftmost is the natural thread, 2nd from left is thread with a wee bit of ink added on lower and top edges, 3rd from left is same as 2nd example except that I have heat set with an iron, 4th is same as the 2nd example where I have air dried the ink rather than heat set it. Now a closeup of example 3 and 4 BEFORE I rinse them.
Now a closeup after rinsing.
Seems okay to me but I think I would conduct this same experiment with darker inks before I feel confident. Remember too, this experiment is on poly thread. I would test Rayon similarly before assuming it would hold up well too. I'm pretty confident about cotton as these inks seem to love natural fibers.
Some inked thread incorporated into the current project.