Something many people don't realize is there is quite a bit of science behind the work that we do. When we first do a walkthrough after a water damage incident, we create what is called a "moisture map". This map essentially tells our technicians the shape and extent of the water damage.
In addition to traditional moisture meters, our franchise uses a FLIR (or infrared) camera. The wet areas of the sheetrock show up as dark on FLIR, indicating they are cooler than the surrounding materials. In this way, we are able to "see" the water invisible to the naked eye.