VARNISH - OLD AGING PRODUCTS IN MINERAL OILS
Gel or resin-like or solid coating deposits that form in a fluid system are often referred to as varnish. The cause of these varnish deposits is related to oil aging which can be determined through laboratory testing of the oil. Reducing varnish in the hydraulic system can be accomplished through oil care measures including dewatering and degassing of the fluid, coupled with avoiding electrostatic discharge and elevated oil temperatures. Existing varnish can be lowered with materials such as fine filtration and /or adsorption methods, besides others.