Drying Time Recorders

When developing a process, it is often important to know the exact time it takes for the coating to dry or cure. There are many stages to the coating drying time. Once a coating has been applied, the first stage is that the coating levels off under gravity. Once a coating begins to cure, a thin dry film appears on the surface. The coating then continues to dry and finally after a period of time, the coating is totally cured. But how do you know when a coating is totally dry