Id the fiber first,
If you do decide to clean it, treat and clean it like a cellulose fiber (raw/unprocessed cotton[Haitian cotton])
Do thorough vacuuming, and if possible (recommended) use a rug badger.
Use proper chemistry to help prevent cellulose browning.
Because it is a regenerate fiber (just a bit superior than Rayon) Its a Bit higher quality than Rayon)
I would not be too aggressive and I would not over wet it. I would dry it facing a clean floor with the air blowers floating it, just in case it browns it would wick into the base of the fibers.
definitely have them sign a waiver. I usually charge $4.50 per sq ft if I clean in my wash plant but with viscose it rises to $5.75 per sq ft and I explain to them the disclaimer and have them sign the waiver.
Looks like its already suffering from Lignin issues ( cellulose browning)
take notes, photos and document it very well, but if you're not sure pass on it
Big negative on bonnets in viscose. They are a weak fiber (paper) that even a wand can create permanent pile distortion. This rug can be washed, but will likely not look much better. As others have said.... Clean with some improvement in appearance. This is the problem with viscose....permanent wear VERY QUICKLY.
Sorry, but I have to ask, have you ever actually done what you're talking about on a trashed viscose? If you ever get a chance I'd like to see the before and after on it. I've never heard of anyone doing anything even remotely as aggressive as that on viscose. Honestly, I seriously doubt a disclaimer would do any real good even if they signed it, but I'm not an attorney either. Personally I don't need money so bad that I would do that rug. I'd tell em it's ruined and be done with it. I wouldn't attempt to restore the unrestoreable. If I can't do em any real good why bother to try?
Btw, I barely see any viscose in my area and personally I hope it STAYS that way!!!
That’s the best thing to do. Better to be honest up front with them than take money from a disappointed customer. I’ve picked up many loyal customers from situations like this. They now know they can trust you and will hopefully call you for all their cleaning needs in the future.