I've been experimenting happily with the Printables paper from Freestyle photo (which I found through APUG, so, Sean, your advertisers do get business here). Other than difficulties determining exposure (especially with spring weather here, which can become overcast in 15 minutes), I am pretty happy. But a couple of my prints have dried with a greyish stain in places that looks almost like mildew. Drying times have only been a few hours, so I don't think that is it. Does anyone have any ideas what it is or how to prevent/remove it?

Also, I spilled a little lemon juice on a print (trying to do too many things at once) and got an interesting yellow cast, which did eventually wash off. Has anyone played with this effect intentionally?