Marker Pens for nylon products
With many people trying to mark their equipment for logbooks and security, the question of marker pens and the effect they have on rope and webbing has been around for a long time.
Bluewater Products have posted the following in their FAQ's section.
Marking pens are fine to use on ropes as long as they are water based laundry markers. Years ago solvent based markers were the norm. Some of the solvents used in these old pens could reduce the strength of the sheath strands marked. These days most pens are water based so this is not as much of an issue as in years passed. We recommend a Sharpie "rub a dub" laundry marking pen.