What type of varnish is traditionally used on wood parts of boats to resist weathering?

Spar varnish is specifically designed for use on wood components of boats and is formulated to withstand the harsh marine environment. Its composition includes added flexibility, which allows it to expand and contract with the wood, thus preventing cracking and peeling caused by temperature fluctuations, humidity, and exposure to saltwater.

Moreover, spar varnish contains a higher amount of UV blockers compared to other types of varnish, which helps protect the wood from sun damage and fading. This protection is crucial for maintaining the integrity and appearance of wooden boat parts that are constantly exposed to the elements.

In contrast, other varnishes like polyurethane, shellac, and acrylic varnish may not offer the same level of durability or flexibility required for marine applications, making them less suitable for wooden boat finishes.