I always allow my bottles and kegs to drain well but sometimes wonder if left too long the star san sort of forms a slimy coating. I have noticed this when I have left the star san in contact with what ever I had the star san in, say a large measuring jug... takes a lot of cleaning off! I will say I have not noticed anything amiss but wanted to get a heads up. I used to use a bucket of water with metabisulphite back in the day and never had an issue but it seems these days you must use a sanitiser.
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I did see one homebrewing video where the American brewer actually said " don't fear the foam it is good for your yeast" is that actually true?
I once left half a litre of starsan in a fermenter and only realised after I had transferred the wort. It was only a 12L batch so a fair chunk of the volume. It fermented with no issues and tasted fine. Starsan, when made up to final strength, is essentially flavourless and food safe. I doubt much survives the fermentation process.
I always use starsan or chemsan in the correct dilution for use in my blow off bottles. I recently found a used bottle,no lid,that had been sat in the depths of my garage (well hidden behind something on my brew bench!) for at least 8 months. If it was just water by then it would have kick started an ecosystem with stuff starting to grow. It was absolutely clear! So there's definitely something in it that kills stuff off!