A blood drop on a hard surface in a normal indoor setting at 20 degrees Celsius is totally dry in 60 minutes, according to a study published in the International Journal of Legal Medicine. The drying time is cut in half when the temperature is raised to 24 degrees Celsius.
According to HowStuffWorks, the amount of time blood takes to dry is dependent on the type of surface it is on, the volume of blood present, the temperature, and the humidity. According to the MadSci Network, the time it takes for blood to dry can also be influenced by the medical problems that the blood donor is suffering from.
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