Electrostatic varnish and precursor detection in lubricants

A method for characterizing a lubricant oil in a lubricating environment, comprising:

• passing a lubricant oil through a volume in a lubricating environment, the volume having a surface comprising an electrostatic accumulator;
• applying, while passing the lubricant oil through the volume in the lubricating environment, a potential difference between at least a first portion of the electrostatic accumulator and a second portion of the electrostatic accumulator for a measurement period of time;
• characterizing, after the measurement period of time, at least a portion of the electrostatic accumulator while maintaining the electrostatic accumulator as a surface of the volume in the lubricating environment wherein characterizing the at least a portion of the electrostatic accumulator comprises optical characterization as measured on the surface of the electrostatic accumulator.