Elsa Beatrice Kidson was born on 18 March 1905 in Christchurch. Her mother, Kitty Esther Hounsell, had some training as a teacher; her father, Charles Kidson, was an accomplished artist and sculptor who taught at the Canterbury College School of Art. Both parents came from hard-working and intelligent families who prized learning. The Kidsons in particular were strongly involved in science, music and art.
In 1908, when Elsa was three, Charles Kidson died. Kitty, left with no continuing income, gave up the family's comfortable Cashmere Hills home and moved with Elsa and her three young brothers to Nelson, where they lived with Charles's father. There she supported the children by schoolteaching. Elsa seems never to have forgotten her mother's industrious and cheerful example, and she and her brothers all worked hard and were determined to succeed.
Elsa Kidson attended Nelson Girls' Central School and in 1918 entered Nelson College for Girls. She did well at high school, gaining a Junior Scholarship which enabled her to begin studies at Canterbury College in 1923. Kidson flourished at university. She became an expert swordswoman and was awarded the Sir George Grey Scholarship and the Haydon Prize in chemistry. She graduated MSc with honours in organic chemistry in 1927.
After working for two years as a demonstrator in chemistry at Canterbury College, Kidson worked for a time for the New Zealand Refrigerating Company at Islington, near Christchurch. In 1931 she joined the Department of Scientific and Industrial Research and was seconded to the chemical staff of the Soil Survey (at that time part of the Geological Survey Branch). She worked at the Cawthron Institute in Nelson, where soil chemists were involved in a survey of the volcanic soils of the central North Island. Kidson, working in collaboration with H. O. Askew and J. K. Dixon, perfected highly sensitive methods for the determination of trace amounts of cobalt in soils and plants. Her meticulous and skilled chemical testing showed conclusively that lack of cobalt in the soil was the cause of the serious wasting disease in sheep and cattle that occurred in volcanic areas of the North Island and in parts of Nelson and Southland.
Elsa Kidson remained at the Cawthron Institute for 34 years. She became a world leader in the research into magnesium deficiency in apples, and did extensive work on the vitamin C content of fruits, the relationship between calcium deficiency and the disease bitter pit in apples, and the link between mineral constituents and nutritional diseases in tomatoes. Her research was of fundamental significance to horticulture and, especially, to the fruit-growing Nelson region.
Kidson was the sole or part author of over 44 scientific papers and in 1952 was awarded the degree of DSc by the University of New Zealand in acknowledgement of the quality of her work. She spent time in 1937 and 1954 working at research stations in Britain, and in 1952 was awarded a travel grant to make a study tour of the United States. She was the first woman fellow of the New Zealand Institute of Chemistry in 1943, and was elected fellow of the Royal Institute of Chemistry in 1944 – the first New Zealand woman to achieve that honour. In 1963 she was awarded fellowship of the Royal Society of New Zealand.
When she retired in 1965 Elsa Kidson was able to develop her interests in art. She studied sculpture at the Wimbledon School of Art in London and on her return to New Zealand became a proficient and imaginative ceramist and sculptor, displaying special skill at sculpting life-sized heads of children. Her knowledge of art and chemistry combined in her unusually glazed and decorated clay works. Throughout her life she was a keen photographer with a special interest in portraiture. She never married.
Elsa Kidson was friendly and outgoing, and always willing to share her skills with colleagues. She possessed a warm sense of humour, and was widely respected and liked. She was involved in a range of community activities, serving as president of Nelson's film and photographic societies, the Nelson branch of the New Zealand Federation of University Women, and the Nelson branch of the Royal Society of New Zealand. Methodist by upbringing, in later life she attended meetings of the Society of Friends. Elsa Kidson died at her home in Nelson on 25 July 1979.