Sealing the Seam
Now that the seam is packed with fresh fiber, he is ready to add the pitch
and seal it. Captain Schaefer, chisels off a few chunks of pitch from a brick. Pitch is a viscoelastic polymer which is derived from coal tar in the process of its distillation. The pitch is put in a can and heated until it is a liquid. It is poured over the seam and left to harden and cool. Sometimes the word pitch is used interchangeably with the word tar, but tar is generally a bit thinner than pitch, while pitch hardens into a solid.