Star San is my sanitizer of choice. It’s food safe and no rinse. Required contact time is one minute. It has worked very well for me for quite some time and I’m convinced that it’s one of the most economical solutions available if you use the spray bottle method [See: Star San Tips, Tricks and Guidelines]
What’s the Shelf Life of Star San?
With regards to mixed Star San Solution: The official answer is probably… you should mix a fresh batch each time you use it. To really test the effectiveness, you need to titrate the solution and test the PPM.
Practically speaking, many homebrewers use and re-use Star San. If you’re going to do that, the solution should be relatively clear and the mixture should have a pH of under 3.5. Previously the recommendation I received from Five Star Chemicals was that the solution should by crystal clear, however, for bottles of Star San not older than 1 year (check the manufacture date on the bottle) crystal clarity isn’t necessarily a requirement.
From “Better Safe Than Sorry” Department: If you doubt a mixture it’s better to be safe, dump it and make a fresh batchMore About Clarity
Years ago, I received this information from Five Star Chemicals: “The cloudy solution could be okay, but it could be bad. The cloudiness is the surfactant coming out of solution. It has reacted, or is reacting with the metals in the water. I don’t know if it is still good, because I don’t know how much surfactant has reacted. I error on the side of caution and suggest that you don’t even mess with it. Use DI water.”
Previously testing the effectiveness of diluted Star San involved two things… Crystal clear solution and pH under 3.5.
As of this update on 9/2018, clarity is not considered an issue – via Emily Lovato at Five Star Chemicals
My personal opinion (not official) is that crystal clear Star San is preferable to cloudy Star San. If you have hard water and your diluted Star San mixture immediately turns cloudy, and you want it to be clear, you can use RO or distilled water.
With regards to Star San concentrate: Five Star Chemicals recommends replacing bottles of Star San concentrate that are over 2 years old. – via Emily Lovato at Five Star Chemicals.
What size to buy? Because of the 1 or 2 year freshness recommendation via Five Star, my recommendation to most homebrewers is to purchase the smaller 8 oz bottle of Star San. If you’re using the spray bottle method [See: Star San Tips, Tricks and Guidelines] 8 ounces of Star San should last many homebrewers for at least a year. My reasoning on the 8 oz recommendation is… why buy a larger bottle that you won’t be able to get through before it needs to be replaced? There’s a calculator in my tips post to help you estimate your usage.
Testing pH of your diluted Star San Mixture…
Testing pH question involves using either a pH meter or strips. The pH meter option is straightforward [See: Amazon’s Best Sellers in Lab pH Meters]. pH Meters can be costly and do require calibration, maintenance and, eventually, replacement. Because of that, I wanted to find pH strips that work well for this task. I ended up trying a few different styles and manufacturers before finding strips that I think work well.
I settled on Hydrion Pro 9200 (0.0 to 6) pH Indicator Strips – via Amazon