Properties and uses of tar

Tar is a dark, viscous liquid obtained by destructive distillation of coal, wood or peat.

Properties

• Black to dark brown viscous liquid, more fluid than bitumen, with a strong odour.
• Good adhesion to aggregate, and quickly penetrates surfaces.
• Waterproof, and resists decay by insects and fungi (acts as a preservative).
• Highly temperature-sensitive: soft in heat and brittle in cold.
• Weathers and ages faster than bitumen; toxic and harmful if inhaled or touched.
• Cheap.

Uses

• Priming and surface dressing on roads, and road patching.
• Preservative on timber poles, sleepers and fence posts.
• Coating on iron pipes and tanks to prevent rust.
• Tarred felt and waterproof coating for roofs.