Gents, I very much liked Double-D's TV test for wads. I am very much of the old school concerning safety and the general "iffy-ness" of wads for blanks. Please allow me to suggest a safe and simple solution to the over-powder wad question for blanks--dry grits.
Make a 2-wrap aluminum foil cylinder with a flat, crimped bottom over a sub-caliber wooden mandrel. Fill it with dry grits--I have found that a volume about twice bore diameter is satisfactory, but you may want to start with less and work up. I would use no more than what gives you a satisfactory report. Twist the end shut and cut with shears.
Load over the charge. A stroke of the ramrod breaks the foil and when the gun is fired, the grits instantly turns into dust and the foil container mostly disintegrates (I occasionally police up a small fragment or two of aluminum foil, usually there is no trace.) I have fired over water, and all the grits is gathered on the surface of the water just a few feet from the muzzle. It does not catch on fire, it is cheap, it is good for the environment, and yes, I would crush the foil container in my hand and throw it at my TV.
There is no truth to the rumor that Jim-Dandy Grits works better than Quaker Grits because it is manufactured in the South....