Tesoro was named assistant director at Onyx Oil and Chemical Company in 1957, cementing her leadership in industrial chemistry.
In 1957, Giuliana Tesoro was named assistant director at Onyx Oil and Chemical Company, further consolidating her position as one of the most senior women in American industrial chemistry at the time. This role placed her among the top research leadership of the company, overseeing multiple research programs related to synthetic fiber and textile chemical treatments.
Throughout this period, Tesoro continued to file patents covering innovations in flame retardancy, antistatic finishes, and dye-fiber interactions — work that would prove foundational to the modern textile chemical industry. Her ability to combine deep scientific expertise with effective research management distinguished her among her peers.
Her appointment as assistant director reflected not only her scientific accomplishments but also the trust placed in her by corporate leadership to guide strategic research decisions. In an era when women scientists rarely reached upper management in industrial research settings, Tesoro's career at Onyx stood as a powerful exception, paving the way for her eventual transition into academia, where she would continue to influence the next generation of chemists and engineers at MIT and the Polytechnic Institute of New York University.