I tried charcoal from my wood boiler yesterday and it worked great, a nice black line on fresh wood. I didn't try it on grey wood or bark, will do it today. I may even crush some and fill a reel. Rubbing charcoal on a string is about as messy as filling the reel with chalk from the gallon jug.

Is there historic pretension for using charcoal for chalk lines? Or am I completely imagining the possibility.

My grandfathers half ball of chalk had lines in it as well. Tim