I thought of several options for putting an emission spectrum on a collar, including fabric paint and machine sewing, but eventually settled on using embroidery floss. The floss would make the lines stand out more than simply sewing back and forth over the collar and I won't have to worry about the pup ingesting paint. The hardest part was actually picking colors of floss to match the emission lines!
Part of the reason my friend asked me to do this project was because I'm
For each line, I used 3 strands of floss and went over the line 1 to 3 times, depending on its relative spectral intensity. Hopefully this embroidery stands up to the exuberance of a puppy.
I'm really happy with how this project turned out and I hope my friend (and his dog) also like it. It was an interesting challenge and a different project from the ones I normally craft.