Cobalt Chloride Paper I used about 5 sheets out of the 200 sheets I had. Almost unused. I bought it for a science test, but I hardly used it. I am not very knowledgeable about science, but here is an explanation of cobalt chloride paper (quoted from the net): ● Test paper made by soaking filter paper in a cobalt chloride (CoCl2) solution and drying it. It is blue when dry, and turns red when it absorbs moisture. This property of cobalt chloride can be used to check if a substance contains water. ● How to use Take it out of the container just before use. Hold the cobalt chloride paper with tweezers and touch it to the substance you want to examine, or let it soak in. If water is present, the cobalt chloride paper will change color to red. ● Precautions It cannot be reused once used. It will absorb moisture and change color if left in the air, so take out only the amount you need just before use. If you draw a picture of a cat on filter paper with cobalt chloride solution, the color will change depending on the humidity in the air, so it can be used as a weather cat. ● Management Avoid moisture and store it sealed in a desiccator with a desiccant. ● Disposal method Dispose of it as combustible waste. The color was white to light pink from the time I bought it. I think it's better to dry it with a hair dryer, etc., and turn it blue before using it. To be honest, I don't know if it's just this manufacturer's product, but the color when opened is white or light pink (the images on Amazon and Monotaro are also light pink, and it says to dry it with a hair dryer before using it). I looked it up and dried it with a hair dryer to turn it blue, and then I tried to see the color change to red when exposed to water, but maybe I did it wrong, but it was a light pink color, and the change didn't seem to be very clear. However, my child did memorize that it turns blue when dried and red with water, lol. I didn't really understand how to handle it either, but I will give it to someone who wants a small amount of cobalt chloride paper. Therefore, please read the text and purchase it after you are satisfied with the initial color and the experimental results.