 During the Age of Sail, ships' hulls were under frequent attack by shipworm (which affected the structural strength of timbers), and barnacles and various marine weeds (which affected ship speed).Since before the common era, a variety of coatings had been applied to hulls to counter this effect, including pitch, wax, tar, oil, sulfur and arsenic.In the mid 18th century copper sheathing was developed as a defense against such bottom fouling.