I use these to measure the pH of my Kombucha. The first strips I used read accurately until a few months later they started turning purple. I've read that light and air affect them, so I figured that's why you didn't read properly. This happened to the second container. With the 3rd container, the first stripe immediately turned purple. I called Precision Labs, which makes the strips. I explained the situation to them. When I told them the expiration date is 9/12/18 they told me they have no expiration date. They personally sell them fresh and they should keep for about 2 years, whether or not exposed to the sun and air. Now they're sending me a fresh container from the lab. Won't be buying from Midwest Homebrewing again.
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