How do I fix the dyes in a Moroccan rug?

I own a red and blue rug bought from a traditional merchant in North
Saharan Morocco (Zagora to be precise).  I believe it is referred to
as a flatweave rug.  I kept it on top of a fitted carpet, and over the
course of five years and many drink spillages the dyes seeped into the
carpet.

The stain has proved impossible to fully remove even with a
detergent-assisted water vacuum cleaner.  I wish to now fix the dyes
so that when it goes over another carpet or even bare boards it
doesn't repeat the trick.

The only possibility raised during my own informal research was that
saltwater may fix the rug, but was second-hand information so I'd need
more evidence before I try it.

The rug's size means it could be submerged in my bath.  I am based on
the south coast of England and would be prepared to send it within the
UK to get it treated.

Good luck
Dave

Hi Dave,
This site does not recommend salt water:
http://www.pburch.net/dyeing/FAQ/settingdye.shtml

Searching with   dye fixing    will find many websites, also many not helpful.

I am wondering if there is a material to coat the back of the rug that
makes it impervious.  ??

Myoarin