Star San is among the most popular solutions used for sanitization of homebrewing gear and it’s absolutely necessary to own a sanitizer whenever a brewing adventure begins.
Although you don’t need much of Star San (only a few drops in a gallon of water) if you are often brewing it may add up and the idea of reusing Star San may become desired for your budget.
So, is Star San reusable or do you have to prepare a new solution every time?
StarSan is reusable, so you don’t have to throw away the solution of StarSan and the water you used on the last brewing day. However, it’s important to preserve the solution by keeping it in an air-seal container as contact with air will slowly deteriorate its pH values and thus effectiveness.
In other words, the pH values must not change or the primary function which is its acidity which kills bacteria will be lost.
How StarSan works?
Star San is made from phosphoric acid which is food-grade safe and kills any nasty bacteria which could infect your homebrew without negatively affecting homebrew. These acidic properties are what make Star San an effective way of battling bacteria, so it’s essential to preserve the pH values below 3.
In case the pH values go above 3 it means the solution loses its acidic properties and turns more alkaline which makes it ineffective and such Star San shouldn’t be used for homebrewing purposes.
How to store StarSan?
You must store Star San solution in an airtight container as this is the only way to slow down the pH deterioration due to exposure to oxygen. When stored in an airtight container, Star San solution can be stored for up to 3 weeks, but it will already lose effectiveness after a few days when exposed to the air. You can use an empty fermenter for storing purposes just as you would for fermentation or any other container which has an airtight lid.
I like to save some StarSan solution in a spray bottle as it’s airtight and I always have it by hand when I need to sanitize small areas.
Secondly, it’s recommended to make StarSan solution with distilled or pre-boiled water as the chlorine and minerals found in tap water will make the solution cloudy and a bit sticky. However, this is not that important as long as the pH values are below 3.
How to check the pH values to tell if StarSan is good?
By checking the pH value of the Star San solution, you’ll know exactly whether it’s still good to use or if should you make a new solution. Removing the guess is always nice as there’s one less thing to have on mind on a brewing day, so you can focus on the important stuff.
pH testing strips
The only accurate and best way to check the pH values is to use pH testing strips. You can buy these kits even on Amazon and they are pretty cheap, so it’s good to have them by hand because you may not only need them for determining the pH values of StarSan solution, but also for testing water and wort pH values.
Knowing pH values is important for making your own recipes, eliminating the issues of the bad brew such as too alkaline wort, and for minor things such as telling whether the StarSan is still alright. For absolute brewing beginners, unless they are really unlucky with their tap water, this may not be super important as following the existing, rated recipe accounts for other things (like a good ratio of malts which will drop the pH value once added into the water).
So, It’s important not to underestimate the importance of pH in brewing especially when making a recipe or having brewing-poor profile water.
These pH testing strips will change color based on the pH value and you’ll get instructions to know which color presents what value, super simple to use.
Red Cabbage Juice method
You may remember this method being thought in high schools or at least mentioned. The Red cabbage has a pigment called flavin which changes the color depending on the pH value it’s in contact with.
This is not the most accurate method as you’ll see because of the small difference such a single number on the pH scale can mean the difference between an effective and ineffective solution.
However, this way you can get a guess on whether is Star San solution still good or if is it completely unusable in case the pH value is way above 3.
So, mix some solution with cabbage juice and the color will change to pink with the pH between 1 and 2, dark red from 3 to 4, and violet from 5 to 7. Star San mixed with water has a value between 2.5 and 3, so pink is safe and dark red could be a safe way to go too, but it’s not completely accurate and you may risk a bit. However, in most cases, if the solution was in contact with oxygen and is bad, it will be above 4.
Final take on
You can now reuse Star San without preparing a new solution each time as long as you store it in an airtight container. PH testing is always recommended and I would personally only reuse the air-sealed solution if I am brewing within the next 2 weeks. For anything greater than that it’s good to have pH stripes by hand because risking on such inexpensive stuff (unless you are making gallons of solution every time) is not worth it.