Genesis says Noah coated the Ark with pitch inside and outside. The instruction appears in Genesis 6:14, immediately after the command to build the vessel from gopher wood.
Pitch is a tar-like waterproofing substance produced from petroleum, wood, or other organic materials, depending on the ancient process. In the biblical story it seals the Ark’s wooden surfaces against water during the Flood.
The Hebrew term translated “pitch” is related to the word for atonement or covering in some interpretations, creating a possible literary wordplay. Translators nevertheless differ in the exact English wording, using terms such as bitumen or resin.
The coating is distinct from the Ark’s timber. Genesis therefore gives both a construction material and a sealing treatment, a detail often omitted in simplified retellings.