First, time and rope has changed over the years, so what was accepted practice ages ago may well be superseded now.
Mr Cosmic said:
This is often the case, but if you remember to ask next time, then they will say "Oh yes one came with the reel, we usually through it away". These will give you essential instructions in care of the rope.
Mr Cosmic said:
The tape inside the rope (a clear plastic tape about 3mm wide) doesn't have anything printed on it, at least not on the first 6 inches. The rope does have a green thread mixed in with core, which IIRC indicates the year of manufacture.
Forget the threads, your recollection is long out of date (pre 1998). The tape will have at every 1 metre or less (often around 0.3 m), a set of data printed on it which will include name of manufacture (hopefully Edelrig), date of manufacture (hopefully 2007), the Standard it is manufactured to meet (hopefully BS EN 1891:1998 but it might not have the initials), the type of rope (you should have A not B since A is stronger) and name of material it made of (should be polyamide).
Sorry to expose you like this, but I hope others will learn from your experience. The date is important - I was sold by some one a rope which was 5 years old! As some manufacturers only recommend a life time of 5 years, always check this date! The date should also be on the reel but you are then reliant on the shop not having reused a reel.
But to answer your question.
First, the standard does require the shrinkage to be specified though it gives no maximum value which the rope is required to meet. Of more value, the standard says the test to determine shrinkage is to to submerge the rope in clean water within a temperature range of 15 +/- 5 degrees C and pH range of 5.5 to 8 for a period of 24 +/- 0.2 hours. So that gives you a guide to soaking times and conditions.
Second, from a 5 year old Edelrig leaflet, it gives no info on pre washing. Shrinkage for uncoloured 10 mm superstatic was cited at 2.3%.
The leaflet also says "wash dirt ropes in hand warm water with neutral soap, rinse thoroughly, dry at room temperature in a shady place. Halogen free disinfectants are not harmful."
I have not done any work on how water is absorbed by rope, so 24 hours seems as good as any thing. I soak samples for testing for 2 or more hours, but that was based on what Owen Clark told me. As you may be aware, most ropes are made with the aid of a lubricant. I recall some people claim the lubricant does make the rope more slippery to use, so getting rid of it has some benefit. Running a wet rope under tension through a pulley has possible value in "washing" this lubricant out where as simple soaking may not. (There is also the lesser problem of the sheath moving with respect to the core, which the pulley trick might help to settle down; though I have no information either way on this point. My 5 year old Edelrig leaflet cites 0% slippage however. But the standard indicates this is likely to mean less than 0.1% or 10 cm overall in your new rope - hope my maths is correct.) I know some people put a rope through their washing machine (pre clean the machine free of all washing powder first though). I have no recommendations, but doing the pulley trick twice under water say 12 hours after starting soaking and leaving it for another 12 hours a fresh water seems to be a suitable compromise if you want to shrink the rope, otherwise the clean washing machine is faster.
In the first instance I would suggest a phone call to the shop you brought the rope from; they should have the leaflet some where and be able to quote shrinkage. So the question becomes is shrinkage really an issue? Or put it another way, how accurate do you know the pitch plus rigging length?
What I can't answer is does rope shrink further after its first wetting and drying cycle or indeed after use. Oh god, another possible piece of work. Any one interested in doing a simple experiment? If so, please PM me.
Lastly to other readers, other manufacturer's rope do shrink more than 2.3%, so read the leaflet!