Density is the weight per unit volume at a specified temperature. Density determination is important measurement to convert weight into a volume unit. When coatings are manufactured the raw materials are measured in weight units to control the process. The finished product is usually sold in volume units. In accurate density volume measurement is fundamental to an efficient operation. A density cup has also been described as a liquid pycnometer. In North America a weight per gallon cup is commonly used name. An ISO cup is a popular design globally. All the density cup designs work the same way having a precisely made cup with small hole in the lid to allow for removal of excess liquid and air.