What is the Difference Between Spar Varnish and Spar Urethane

The key difference between spar varnish and spar urethane is that spar varnish tends to chip or chalk off over time, whereas spar urethane tends to remain a hard, shiny surface.

Although we are describing spar varnish and spar urethane as separate terms in this article, spar urethane is actually a type of spar varnish. In this article, we are discussing the properties of older forms of spar varnish and modern spar urethane.

CONTENTS

1. Overview and Key Difference
2. What is Spar Varnish
3. What is Spar Urethane
4. Spar Varnish vs Spar Urethane in Tabular Form
5. Summary – Spar Varnish vs Spar Urethane

What is Spar Varnish?

Spar varnish can be described as a wood-finishing varnish that was originally developed for the coating of the spars of sailing ships. Occasionally, spar varnish is also named boat varnish or yacht varnish. Spar varnish has uses in application on masts and rigging, and it can withstand rough conditions as well. Moreover, spar varnish allows objects to be flexed by wind loads they supported, effects of the sea and bad weather, and the effects coming from UV degradation from long-term exposure to sunlight.

To resist flexing, the varnish needs to be flexible and elastic. If the varnish is not elastic enough, it will soon crack, allowing the water to penetrate to the wood beneath. At early times, there were no simple materials that were easy to work with. Therefore, varnish production was rudimentary. However, this was vastly improved after the developments in modern polymer chemistry.

Originally, spar varnish appeared as a short oil consisting of a small amount of finishing oil such as boiled linseed oil. This finishing oil gave flexibility to the varnish. However, its weather resistance was still poor. Therefore, it needed to be re-coated frequently.

At present, spar varnish is used for any outdoor wood finish in North America. The modern spar varnish is excellent in weather resistance and UV resistance, although its flexibility is not desirable. Spar urethane is a modern type of spar varnish.

What is Spar Urethane?

Spar urethane is a type of spar varnish that consists of a polyurethane-based finish that is intended to use outdoors. Therefore, this material is resistant to sunlight, heat, and water. This resistance is the most important property of spar urethane.

Figure 01: A Table Varnished with Spar Urethane

Typically, polyurethane varnishes are hard, abrasion-resistant, and durable. This type of varnish is popularly used for hardwood floors. However, some wood finishers think this substance is difficult to handle and unsuitable for the finishing of furniture or other detailed pieces.

What is the Difference Between Spar Varnish and Spar Urethane?

Spar varnish is a wood-finishing varnish that was originally developed for the coating of the spars of sailing ships, while spar urethane is a type of spar varnish that consists of a polyurethane-based finish that is intended to use in outdoors. Therefore, spar urethane is a modern form of spar varnish. The key difference between spar varnish and spar urethane is that spar varnish tends to chip or chalk off over time, whereas spar urethane tends to remain a hard, shiny surface. While Spar varnish has comparatively low weather resistance and UV resistance, spar urethane has excellent weather resistance and UV resistance.

The below infographic presents the differences between spar varnish and spar urethane in tabular form for side by side comparison.

Summary – Spar Varnish vs Spar Urethane

Spar varnish is a wood-finishing varnish that was originally developed for the coating of the spars of sailing ships. The key difference between spar varnish and spar urethane is that spar varnish tends to become chip or chalk off over time, whereas spar urethane tends to remain a hard, shiny surface.