I think Ricky has given you the best advice.
With silk you need to treat it with respect (in some cases that means turning the pressure washer down a bit
) but the most important thing is GROOM GROOM GROOM.
You need to extract as much water out as you can immediately during cleaning, re-set the pile to dry, possibly re-groom during drying, and then finally groom again when completely dry.
I am a qualified Master Rug Cleaner and I'll be honest, even I am very cautious taking on a silk.
You need to pre-qualify with the customer that there may well be a permanent texture change, but you will carry out the work in a way that will minimise this. The benefit to the rug from cleaning needs to outweigh the possible ill effects of water on the silk.
PS you should ALWAYS work in the direction of the pile, and NEVER any other direction.
PPS I would be fascinated to see a picture of this rug if it could show this difference in the direction of pile. I suspect this may be pile reversal, I seriously doubt it could have been made like this.
If you understand how rugs are woven on a loom, you would share my disbelief that a rug's pile can be manufactured in such a manner!! (put aside half an hour to watch JB's thread on rug manufacture, on cleantalk)