Liquids build up a specific ohmic resistance to the electric current, depending on the applied voltage. The reciprocal value is the conductivity. The measured resistance depends on the geometric arrangement of the electrodes within the measuring cell. In order to be independent of the measuring cell, the measured resistance has to be divided by the cell constant “C” which yields specific resistance. The BYK LC 2 conductivity meter is for solvent-based coatings only. The conductivity test is easy to perform.
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.
The various stages of drying and curing that occur in films are easy to detect but difficult to define in terms of chemical and physical principles. Several factors such as oxidation, evaporation, and polymerization impact the drying time. Additional physical factors impact the drying time: wet film thickness, substrate, temperature, humidity, air circulation and light exposure. In order to evaluate the objectively it is necessary to use dry time recorder under controlled conditions.