In reply to Piers Harley: most if not all dry treatments have a very similar base and for most if not all to be well bonded to the item they are used on they need some form of heat application like tumble drying. This would obviously not be advised on a rope so I would suggest that a wash in dry treatment would offer very good results when first used but it would wear of quickly and return to it original or near original performance.
I would suggest you pay a bit extra in the future and get a good dry treated rope.