While no significant variations in strength were found, sulphur and porosity were found to be of prime importance in causing embrittlement of cast high-purity copper. More than 1·8% porosity (density <8·80g cm−3) limited the ductility to no more than about 25% reduction in area (RA). More than 4ppm sulphur limited the ductility to no more than about 25%RA, which declined further as sulphur increased. With increasing oxygen content, while maintaining low sulphur content and high density, 100%RA was obtained up to an oxygen content of 280ppm. Above that oxygen level the ductility dropped to an average of about 35%RA.
