I wanted to share my latest change in film washing protocol because it worked so well. I was getting occasional drying mark and contaminants when drying film. I wash my film carefully in running tap water and tried varying concentration of Photo-flo and that didn't always work. I finally found a way that works for me on consistent basis. I wash my film under running water as usual. When washing is completely done, I empty the tank and pour in store bought and bottled distilled water (the kind you drink) in it. Let it sit for 30 seconds or so and empty. Do it again and this time, add 0.5 ml (8 oz can) or 1 ml (16 oz can) of Photo-flo and let it sit for 60 seconds. Pull it out and let dry hanging vertically. This will end up in 1:500 concentration. I measure this small amount of Photo-flo using plastic pipette that I bought bulk ($20 for 500 or something). It's not accurate, so approximate will do. I've been enjoying blemish free wash for a while using this method.