Tow is a plant fiber that was traditionally used in sealing the planks of wooden boats and ships. It was used to stuff in the cracks, and then sealed with tar. It is used in sealing the seams of iron pipe joings in sanitary piping with lead still today. Jainly it is jute, but it can be made from a number of plant fibers. It is used by shooters, particularly those who shoot fowlers or other smoothbore guns, for cleaning instead of using cloth patches. It can be washed out dried and used again. Some riflemen also use tow for cleaing, although the rifling is hard on the fibers, and it cannot be expected to last as long as being used in a smoothie. And, as indicated, there is some historical accounts of using Tow for wadding with a round ball. Since the Tow performs the same function as a cloth patch, this seems possible, although its hard to believe it would provide much of a seal against gases, by itself. Used in conjunction with wasp nest, or some other sealing substance, it should work fine.
The question always asked by practical historians is what did shooters use when they were far from a supply of cloth for patches? In the colonies, particularly in the early years( 1600s) the only cloth had to be shipped in from England, while clothe made here was homespun, and rather coarse by comparison. I have always suspected that the thin hide from small animals, like rabbit, squirrel, ground hog, etc. were the source of patching material in the boonies, but I have not found a historical reference to this yet. We know that even deer hide can make a good patch, and they are often reusable, no small factor for people living off the land.