Sprite Stitch Board!

Hi guys
I am in the process of making a big cross stitch. Problem is its got a touch grubby
How do I go about cleaning it without making the colours of the threads run?

If you've used DMC thread, I haven't had any trouble with threads running when washed with gentle soap in the tub.

There's a guide our Lord Libidan wrote about stain removal, but it's techniques are just as good for grubbiness too.

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