In the Book of Genesis, Noah’s Ark was coated with pitch to make it watertight.
Genesis 6:14 instructs Noah to build the Ark from gopher wood and to cover it with pitch inside and out. Pitch is a waterproofing substance made from a tar-like or resinous material, so the instruction gives the vessel a protective seal against water.
The verse uses the Hebrew term kofer, commonly translated as “pitch.” English translations differ slightly in wording, but “pitch” is the standard answer in English-language references. The passage does not identify a modern chemical formula or a precisely documented ancient manufacturing process.
The Ark’s coating is often confused with its construction wood. Genesis names pitch as the sealing material and gopher wood as the building material. Because the identity of “gopher wood” is uncertain, the two details should be kept separate: one concerns waterproofing, the other concerns the Ark’s timber.