Is there a pen/pencil that will not burn off in a kiln?

I have a bunch of glazes that i just got that i have no idea what the colors are they are numbered but no color name is listed, there is a mix of high fire and low fire, tomorrow i plan to fire a bunch of chips of the lowfire glaze i was wondering if anyone knew if there is a type of pen or pencil that i could use to write the glaze numbers on the back so i know what chip is what color (the chips im using are from an already fired piece so i cant carve the numbers in) thanks