Glow sticks are not flashlights. They are designed to emit *useful* light that is sufficient for specific tasks. An uncontrolled chemical reaction takes place and the light is very bright for the first few minutes and then quickly drops to operating levels after about an hour. . It will continue to fade until the chemicals run out. They are rated (tested) at a specific temperature - 75 F. Temperature is GREAT. Cold temperatures produce less light but longer. Higher temperatures give more light but in less time. I have used hundreds of these lamps in the field. Here are the test results for the yellow sticks. The test was conducted at 75F. This was done in a 6ft x 9ft bathroom with cream walls and no windows (total darkness) during the day. I gave my eyes 5 minutes to get used to each test. Note that the results are even "better" if you enable full dark adaptation. Using the antibiotic tube as a reading test (product information, instructions) I was able to read them anywhere in the room. 1 hour - Apparent brightness has decreased by at least 50% after one hour, as expected. I could read the fine print on the tube about 2 feet from the light source. 3 hours - apparent brightness decreased by about 75%. I could read the tube about 1 foot from the light. At this level, I could easily complete tasks like washing my hands or even taking a shower. The detail of most objects was not visible at long distances - ie I could see the towels but not the texture of the terry cloth 9h - I could read the tube about 2 inches from the light. It was bright enough for tasks like washing hands and I could easily see everyday objects like toothpaste, shampoo bottles, faucet handles. I could read large text on soap bottles from a few feet away. So. I decided to take a shower! Since being in the bathroom for about 15 minutes my eyes have adjusted better. I had no problems with the shower and could easily see important things. I couldn't see the water flow due to the lack of contrast; no soap bubbles, no strands of hair, etc. I could see the floor, bath mat, etc. without any problems. 12 hours - could read first aid kit 1 inch from light. There was still enough light to see important things - the floor, doors, door handles, etc. There was enough light to cast a faint shadow from my hand across the room at about 8 feet away. although the door/doorknob. Now the most interesting. After 24 hours, I warmed the glow stick with body heat and it brightened up to about the 12 o'clock mark. Then I put it under hot tap water (about 120 F) for about 2 hours. minutes and it brightened up to about the 9 o'clock mark. And then at 11pm when it was very dark I put it in a pot of 180 degree water (just boiled) and it lightened up to about the 5am mark. Of course it has faded to its previous level upon cooling. They are made in China and have no date or batch code. The color of the packaging indicates the color of the glowstick, there are actually no words on the packaging to indicate the color. There is a short ribbon in each packaged tube, which is very convenient. In short, they're just as good as the more expensive glowsticks as long as you don't find any broken ones.
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