This is my first test with the Lumi Inkodye stuff, which is light sensitive dye intended for use on fabrics. I used a piece of off-white cotton ribbon I’d bought with this intention, and cut my letters out of paper. I drew my letters in black india ink using a flat tip brush - since I didn’t realize I had markers with that shape at the time - and then cut them out.
The lighter pink images are from leaving the ribbon in weak, non-direct sunlight for about 30 minutes. The darker red is from leaving it in direct sunlight for about 8 hours (while I was at work). The amount of sunlight is the only thing that makes a difference to the colour, rather than the amount of ink.
You can see that although I didn’t cut the counters of my letters out, there’s still a difference from where there was black ink, blocking out more sunlight, than where there wasn’t. I guess even a little sunlight penetrating something relatively thick will make a difference with the right amount of time. The last few photos are after I washed it and some of the ink had faded away with the detergent.