My blinds were really dirty. Must have had a smoker as a previous owner. Blinds were alabaster white with heavy yellow staining.
Removed valances and blinds and put blinds in a small pool filled with water and about 4 cups of oxy clean. Let soak for 1-2 hours.
Used oxy clean spray as a spot treater on any remaining stains.
When I pulled them out of the water I put them on a long table and folded them back like they go. I then zip tied them so the pleats dried in the proper position. Next day I hung them back up.
They came out like new!! The threads and all are white again.