White silica gel desiccant is a non-indicating desiccant. It means that when the gel adsorbs water the color of the gel will not change. This kind of silica gel desiccant is commonly used in preserving some items and to reduce humidity. You can find white silica gel in small packets when you buy some products.
Blue silica gel desiccant has cobalt chloride. The reason why cobalt chloride is required in making blue gel is that it allows the blue silica gel change its color to pink when it reached its maximized adsorption capacity. Therefore, it is an indicating silica gel desiccant which show you when it’s reached maximum adsorption. It can be reactivated with heat to dry out the moisture. Do not use blue silica gel desiccant around food since the cobalt chloride is poisonous.
