Probably get locked up for this... but I've just mixed up a solution of 1.09g of seachem safe in 100ml of boiled and cooled water, so probably 5x the strength of prime. Going to test this and see what happens , also put a bit on a sponge to see if it reacts with cellulose.
Edit: my maths is way out, will correct tomorrow.
In the meantime let's try it with 5g of safe.
Extra edit... 5g in 100ml of water is about 25% stronger than prime. Sorry for the confusion.
I've been following this thread, it's absolutely hilarious! Goodness knows what the op thinks regarding their original question....it's got completely out of hand!!
I now have an indelible image of all male fish keepers dancing round in their undercrackers (or a manikini if they're daring) at water change time & all female fish keepers pirouetting in their bloomers! 😂🤣
So test no2 (seachem safe) has dried out and hasn't left any stains, will do as @MirandaB suggests and put it through the laundry, hopefully in the interest of science it will come out with a tie-dye pattern.