Ironically, as Virginia fired more of its onboard ordnance, the ship became more vulnerable to attack

Virginia has only equipped the explosive shell because it was anticipated that she would only encounter wooden ships. Double plates, each 2 in (51 mm) thick, were used in place of the armor plating, which was initially intended to be 1 in (25 mm) thick and be supported by 24 in (61 cm) of iron and pine. 14 gunports—four on each broadside, three front, and three aft—were punched through the armor.

When fully loaded, Virginia's iron plate barely reached its waterline, in contrast to the Monitor, whose belt of armor extended well below its waterline. Virginia would use 350lbs of ordnance each broadside. Virginia also reduced its cargo by 5 tons after two hours of shooting on the Monitor and other adjacent ships. Ironically, the ship's vulnerability increased as it got lighter. The ship's unprotected sides below the iron casemate could have been more easily pierced because they were more visible above the water as it became lighter.