i put in several with the first wash. my hubby was always buying new t-shirts & throwing them in laundry w/o telling me there were new t-shirts waiting to fade on other clothes. so one time i put ten color catchers in with his 3 new shirts & nothing else, ran full load size water and every catcher turned dark blue/purple. i had them neatly laying on kitchen counter when he got home from work. i've never had another issue with his surprises in the laundry hamper. i wash loads of large scraps w lots of catchers ..larger the load, the more catchers. if they don't turn color i'll use them again. and again if still not colored. they turn color or look dirty gray i toss them. i just wish i had heard of them sooner, i don't know how many t-shirts i bought for me ...pretty color w white inserts or cuffs that turned color after prewash before adding to laundry.