In the Genesis Flood story, Noah was instructed to cover the Ark with pitch inside and outside.
Genesis 6:14 tells Noah to make the ark from gopher wood and cover it with pitch, both inside and outside. The coating is presented as part of the vessel’s construction instructions and would serve a practical waterproofing function in the narrative.
The Hebrew word translated as pitch is related to a substance used for sealing or coating. English translations vary in small details, but the central material is consistently rendered as pitch, bitumen, or a closely related waterproofing substance. “Pitch” is the conventional concise answer.
This instruction is sometimes confused with the ark’s wood because both appear in the same verse. Wood supplies the structure; pitch seals it. Genesis gives no recipe, thickness, application method, or archaeological evidence for a surviving coating.