I have used CorteClean for a number of years with great results but somehow last year during covid-19 I did not use the product and then this year when I cleaned my deck the stains did not come out. So I called Greg the company owner and explained what happened and he said the product I was using was more than a year old and had past the expiration date so it probably was not strong enough to clean the stains. He gave me a special price and I ordered a new bag of the product and applied it exactly according to the instructions using the Four Scoops per gallon ratio and I left it on the deck for one day until it rained and then the next day it came out perfectly spotless ( pictures attached ). Thank you Greg!