Artifact Image 2_Iron ballast_Iziko Published May 29, 2015 at 2804 × 2019 in Artifact Image 2_Iron ballast_Iziko Iron ballast recovered from the São José slave ship wreck undergoing treatment. The ballast was used to weigh down the slave ship and its human cargo. Photo courtesy Iziko Museums Iron ballast recovered from the São José slave ship wreck undergoing treatment. The ballast was used to weigh down the slave ship and its human cargo. Photo courtesy Iziko Museums