Amazes me why you have to solvent clean curtains!!
i certainly dont,
i found the best and most effeciant to use a steamer ,
A good vac first, micro splitter misted on, a gentle aggitatin with micro cloth, then a terry towel wrapped over head of steam tool . simply run down the fabric holding the backing with another terry towel. watch the dirt come of.
not only cleans but dresses the curtains at samr time.
I find another effective way , is to again m/s but use a drymaster hand tool , I guess a cfr would do the same job

geoff