Interesting reading for those who Sharpy their ropes.
NeIce wrote:MARKING OF ROPES
That marking a climbing rope with a felt pen can damage it was first reported in 1998. The German Alpine Cub tested a Sharpie felt pen (made in USA and sold in Germany), which apparently was advertised for use on climbing ropes (to mark the middle of the rope, for instance). In the tests the ropes were marked and the marked area was placed at the orifice plate in the standard UIAA drop test. Five unmarked samples held 10 - 12 falls, while three marked samples held 6 - 8 falls. This information was published at that time in the Gazette of The Alpine Club of Canada as well as in The American Alpine News.
Last year this topic re-appeared on the Internet as well as in Climbing and Rock & Ice. In both magazines the use of felt pens was recommended for the (middle) marking of ropes, while the Internet correspondence centered on the damage. The press, despite being told about the possible damage, did nothing about it. Among the users there was doubt about the sources of the information.
Last year two rope manufacturers (Lanex and Mammut) and the German Alpine Club visited this problem again. Various samples of non-dry and superdry rope were tested using a variety of felt pens (Sharpie was not among them). Testing was done seven to 30 days after application. Reduction varied from zero to 50 % in the number of drops held. Superdry ropes generally had less capacity reduction than non-dry, possibly because the saturation was less. However, one particular rope sample had an insignificant increase in capacity for the non-dry rope, but a 35 % reduction for the superdry. This rope, by the way, was the only one, which did not have a reduction in capacity for both the non-dry and superdry sample.
Middle markings, which come with a new rope and were applied by the manufacturer, are safe. Do rope manufacturers sell trustworthy markers? Mammut tested the "Rope Marker", a pen sold by Beal. The reduction was 50 % for the non-dry and 17 % for the superdry rope. Mammut tested five days and four weeks after application. The capacity reduction was more for tests done four weeks after application.
Sanford, the manufacturer of the Sharpie pens, will apparently not guarantee a consistent product. The ingredients of the pen may vary. There is no "standard" formula for the chemicals that are contained in the markers. The company has also stated that "Sanford will not endorse or in any way recommend use of these markers for rope climbing (sic), and will not accept liabilities, which may arise from its use."
The recommendation: do not mark your rope with any kind of felt pen. Water-soluble acrylic paints are apparently safe. No information is available how long they stay on.
The bottom line: (for a rope, which would be safe under normal circumstances) there is a risk when the marked area is loaded by a fall over an edge. Who buys lottery tickets?