[Star San has three active ingredients: phosphoric acid, DDBSA, and propylene glycol] The acid-ionic [detergent or surfactant] is a synergistic killing machine. The acid by itself will not kill bacteria. The anionic detergent by itself will not kill bacteria. The combination of the two, at the correct ratio, is an absolute stone killer ... [The EPA requires you to make a fresh batch of sanitizer for every use ...] The material is kind of interesting. Like I mentioned before it is a, uh, it is a soap. It’s an acid anionic detergent. Um, if it’s made with deionized water, if the used solution is made with deionized water and there are no minerals in the water itself, um, the used solution is active for literally months. Uh, if there’s minerals in the water, what will happen over a period of time, the minerals will win out over time and they’ll start to create a hard water soap. The hard water soap will make the product cloudy. Only because, just like people use bar soap and they get soap tub rings. It works identically. There’s no difference in the chemical reactions behind it. And any brewer that uses the product and is in a hard water situation, I always tell ‘em to go to the supermarket and buy a jug of deionized water off the shelf. Um, they’ll thank me for it later on — and they do. They call me back up and they say, “Boy the water, you know, the sanitizing solution is crystal clear. Some of ‘em even have pH meters, um, some home brewers. And, uh, they go, “My pH it, uh, remains at 3, um, for two or three months.” I say, “Yeah, you’re still sanitizing. You’re still killing ... You can test the effectiveness in two ways, by the pH, or by the, uh, turbidity of the actual used solution. How cloudy it is.”