I have been using regular Star San for quite awhile. I would say for about the last 8 to 10 batches I have notices what appears to be a thin layer of oil on top of the beer after I transfer to the secondary. There has never been an issue with taste, poor head retention, or anything else. It still bugs me. So I went and got some Io Star San to try. My normal practice is to mix up about 2.5 gallons of sanitizer in a 5 gallon bucket. My guess after researching forums here and other sources on the internet was that the regular Star San was degrading the plastic bucket because it is acidic and therefore causing oil slick looking layer (kinda like what you see when motor oil drips on a puddle of water in a parking lot but not as bad). Today I mixed a little regular Star San in my carboy directly. I used the Io star in the bucket for my auto siphon. The thin layer is still present. Now I am even more frustrated. I really don't think this is affecting the quality of my beer but it is still driving me nuts. I am pretty sure it's not from residual soap as I rinse the h*** out of all my stuff after cleaning. Anyone experienced anything like this? Should I just not worry about it since I don't have any quality issues?
Also with the Io Star San, I am reading at the recommended concentration it requires you to rinse after use. Can I rinse with regular tap water(which is well water for me)?