Varnish Varnish and Sludge, the hidden oil pollutants. There are numerous types of insoluble contaminants found in hydraulic and lubricating systems. Varnish and sludge comprise the various oil degradation by-products and soft pollutants. It is a thin, insoluble film, consisting of long-chain molecules, that, over time, deposits throughout the internal surfaces of a lubrication system. … Sigue leyendo Barniz