In reply to john arran:
> You may well be right but I don't think it's a significant factor for ropes. I've read (sorry, don't have links) a number of reports about testing of old rope that's been left in-situ for years, even decades, and it remaining within or close to its original strength spec. because only the sheath is UV impacted and the main strength is in the core, which is UV shielded by the sheath.
> I wouldn't trust tape that had been in situ a long time and was badly faded.
I linked a report above that actually performed tests and found a correlation with rope strength and UV fading, unfortunately the whole report wasn't available but enough was to see that UV does degrade ropes. Also bear in mind that only a small portion of the sheath need to be damaged to significantly weaken it and a large percentage of a ropes strength is in its sheath.
a 10 second google found this also
http://personal.strath.ac.uk/andrew.mclaren/JMDA75.pdf
"1.6.3 UV light
Signoretti [30] has also examined the effect of UV
exposure on the number of DODERO falls withstood.
He exposed samples of rope to sunlight at mountain
huts in the Dolomites and tested both the static
strength of filaments and the dynamic fall-holding
ability. He reports a 35 per cent decrease in number
of falls after 3 months at the Kostner hut (2250 m),
and 15 per cent reduction in number of falls after
exposure for the same time at the Carestiato hut
(1834 m). He explains the difference with reference
to the intensity of sunlight at different altitudes.
The decrease in dynamic performance of the ropes
is greater than the difference in static strength of
the filaments."
Also consider that a degraded sheath will almost definitely cut more easily.
Post edited at 16:01