What substance was use to caulk the Ark and Moses' basket?

Answer 1

A combination of tar and pitch were used the caulk the papyrus basket he lay in. He was then set afloat among the reeds and was found by the Pharaoh's daughter. When his sister sees the Pharaoh's daughter taking the basket, she inquires if she needs a wet nurse. Upon her agreement, she takes Moses to his birth mother and she becomes his wet nurse.

Answer 2

During the first millennium BCE, when the stories of the Ark and of Moses were being developed, the Dead Sea was a rich source of bitumin. From time to time, large patches of it would rise to the surface and float, to be collected by those who wished. By the middle of the millennium, the Nabateans had established a monopoly on the collection of bitumin from the Dead Sea, fighting off all challengers. Even Alexander the great, who sought to control this prized resource, came to realise that it was better to trade with the Nabateans than to attempt to defeat them. The biblical authors no doubt had this pitch in mind when they wrote of caulking the Ark and the basket.