Hello sir,

I have used graphite in epoxy as a bottom coat, but never tried to glass over it. However, you can get black lines by simply mixing printer toner like what comes out of a laser printer or copier. ONLY A SMALL AMMOUNT. It doesn't take much, and too much weakens the bond.

I have also used paint pigments as well as epoxy-specific pigments. Again only a tiny bit. I literally dip a toothpick in the pigment, then dip in the epoxy and mix it (with microballoons for the filler as normal) and then if I need it darker dip it again. It takes very little.

I have started saving my old printer toner cartridges. I have some magenta, cyan, and yellow from a color printer that I am going to one day use as pigments in the glass on a surfboard or kayak and get a tye dye effect... or maybe an ugly mess... who knows? :)

Since you appear to be going black with this kayak, I suggest doing a bottom coat with graphite mixed in the epoxy. They sell it usually in boating stores in the epoxy section. It makes it much more abrasion resistant.

... and post pics when done!

-Malcolm