heat it for 2 mins. in the microwave. Carefully pour into a spray bottle. Then add 1 c. Dawn dish soap. Spray on to area to be cleaned and let it sit for 2 hours. Rub with a cloth or gentle sponge and they'll look brand new. I have tried many things over the past 7 years to remove the stains and my shower was pretty badly stained by hard water, so it took a couple of times to clean it, but it looks brand new now!