Understanding Corrosion in Water Pipelines: A Guide for Pipeline Designers


Long Oil Varnish

Last updated: February 18, 2018

What Does Long Oil Varnish Mean?

A long oil varnish is a clear liquid that is applied to a material to protect the material's surface. While drying, a long oil varnish forms a transparent film that protects the underling base material. A varnish is comprised of a mixture of oil and resin. The word "long" in long oil varnish indicates a high ratio of oil to resin.


Corrosionpedia Explains Long Oil Varnish

There are three main types oil varnish: long, medium and short. A long oil varnish has the highest ratio of oil to resin when compared with a medium and short oil varnish. This higher ratio of oil to resin creates several differences among the three:

  • A long oil varnish will typically have superior penetration into materials such as wood.
  • A long oil varnish will also have a film that is not as hard as varnishes with less oil.
  • A medium or short oil varnish is not as waterproof as a long oil varnish.

Long oil varnishes are widely used in applications that are exposed to moisture and temperature changes. A long oil varnish is softer than a medium or short oil varnish. This allows it to expand and contract with the base material as temperature fluctuations cause these expansions and contractions to occur. Also, the increased amount of oil helps protect the base material from water. For this reason, long oil varnishes are frequently used for marine applications.


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