What material is oakum primarily made from?

Oakum is primarily made from hemp or jute fibers, which are natural materials derived from plants. Historically, oakum was used in marine and plumbing applications to seal joints and make them watertight, particularly in shipbuilding and pipe fitting. The fibrous structure of hemp or jute allows it to be soaked in tar or other caulking compounds, creating a flexible, durable barrier that can withstand moisture and pressure. This characteristic makes it ideal for use in areas where sealing is critical to maintain structural integrity and prevent leaks.

In contrast, the other materials presented would not provide the necessary properties for traditional oakum applications. Plastic fibers may not offer the same level of flexibility and watertight seal, metal wire lacks the necessary compressibility and absorbency, and wood pulp does not possess the physical strength or fibrous quality required for effective sealing in plumbing. Thus, the use of hemp or jute in making oakum confirms its effectiveness in the intended applications.