For years manufacturers have marketed dry-treated ropes. However, everyone and their brother knows that not all dry-treatments have been equally effective. Yet personal experience aside, there has been no way of knowing how effective various treatments are. That ends now, as UIAA has introduced new water repellent certification.
The test seems to mimick real life surprisingly well. A rope sample is subjected to subject to light abrasion over its entire surface to simulate few days’ use. The rope is then soaked for 15 minutes following a precise procedure. To pass the test at a certified laboratory, the amount of absorbed water must not be greater than 5% of the rope’s weight. For comparison, a non-treated rope absorbs around 50% of water in this test, and many ropes labeled as "dry" can absorb between 20% and 40% of water. Ropes with surface treatment only cannot pass the says according to Beal.
So far only Beal, Edelweiss and Mammut offer certified ropes that I know of. The certification is very new though, so it is entirely possible that some other brands could have equally good treatments but their ropes are yet to be certified.