My colleague, mentor and friend Heidy Mader, who has died aged 61 of cancer, was an outstanding experimental scientist. She applied lessons learned in developing the Wispa chocolate bar as a research physicist at Cadbury to lead a revolution in understanding the flow of lava and magma as a professor at Bristol University.
Heidy was born in Cosford, Shropshire, to Renate (nee Pitz) and Eric Mader. Eric was an officer in the RAF, and Renate, who came from Germany, went on to become a teacher. The family moved frequently within the UK, following Eric’s postings.
For Heidy’s secondary schooling they settled in Germany, where she became fluent in German and passionate about physics. Ignoring the clear message from her teachers that “girls can’t do physics”, she took the subject at Abitur level – the only girl in her year to do so. This was the first of many times in her life that Heidy encountered and dismantled a lazy stereotype of female limitation.
After a first-class degree in physics at the University of York, Heidy joined the technical development department at Cadbury, where she investigated the rheology of bubbly molten chocolate as part of the Wispa development team. Rheology, which describes how materials flow and deform when subject to a force, is little known to the wider public, but cuts across all aspects of our lives, dictating how blood flows around our bodies, how all manner of products – foods, medicines, plastics – are manufactured, and how materials such as ice and magma flow through the natural environment.
Following a PhD at Bristol University on the physical properties of ice, a postdoctoral position researching explosive processes in volcanic eruptions, and a lectureship at the University of Lancaster, in 1996 Heidy returned to Bristol. There, she founded a rheology lab that conducted painstaking experiments on bubble- and particle-laden fluids – proxies for lava and magma.
Like the chocolate destined to become Wispa bars, magma is composed of a crystallising liquid containing bubbles; Heidy’s great insight was that the same rheological techniques she had used at Cadbury could be applied to understanding the flow of magma during volcanic eruptions. The results transformed understanding of magma flows and yielded mathematical models that enabled more accurate prediction of volcanic eruption behaviour.
Heidy was a generous mentor to dozens of younger scientists, sharing her skills and knowledge, and always giving wise counsel, even when this involved speaking uncomfortable truths. She was viewed as a role model for women in science, in part because she demonstrated how “family first” need not mean “career second”, at a time when many in academia still expected women to make that choice.
She and her long-term partner, the mathematician Jon Keating, had three children – the first, Alex, sadly died soon after he was born. In her spare time, Heidy played the bassoon enthusiastically, swam, knitted, made stained glass, baked wonderful cakes, and walked her beloved dog, Tess.
Heidy is survived by Jon, whom she married in 2009, and their children, Rob and Miranda, and by her mother.
