20 x 20 cloth can be cut to size and reused enabling maximum versatility Large cloth size enables you to detect leak patterns in large spaces Let the cloth dry and everything not touched by water will return to blue so you can reuse it ~ it s that easy! Color will change slowly when relatively humidity is over 55% and rapidly when the cloth is wet No color chart or other tools or equipment needed for accurate results Our Cobalt Chloride cloth detects the presence of moisture to determine if you have wetness or dampness problems. Each cloth is 20 x 20 and can be cut into smaller pieces or draped over equipment. Note: The reaction is reversible if exposed to water vapor in less than 100% relative humidity. If the sheets are heated or the surrounding air goes dry these will revert back to their blue color. If splashed or wet they will change in those spots permanently and indicated distinctive white spots.It is a fast and easy way to identify leaks in larger spaces such as roofs between walls inside car doors or under ceramic tiles. The larger cloth allows for identification of spray or leak patterns when left in enclosed spaces.This cloth is responsive to 50% relative humidity and above in addition to any direct exposure to an aqueous solution.Instructions:Place the cloth near recesses or areas where there may be cracks/leaks.If moisture is present the cloth will turn from blue to a light pink/white color.NOTE: Be sure to keep the cloth sealed tightly in the amber bag as exposure to 55 percent relative humidity or greater is sufficient enough to cause a slow color change.