Bernard Cracroft Aston was born on 9 August 1871 at Beckenham, Kent, England, the son of Mary Griffin and her husband, Murray Aston, a stockbroker. Bernard came to Christchurch, New Zealand, with his parents as a boy. He received his secondary education at Christchurch Boys' High School and undertook further studies with the Dunedin Technical Classes Association, qualifying in chemistry and botany. He then attended the University of Otago, although he did not formally enrol and did not take a degree. He was encouraged by James Gow Black, professor of chemistry, who helped him obtain work as a chemist at the Milburn Lime and Cement Company and as a government consulting analyst based at Otago University.
Aston's scientific career began in earnest in 1899 when he was appointed chemist to the Department of Agriculture in Wellington. His primary task was to establish analytical chemical services for the department. In the first few years he travelled abroad on study trips and was responsible, particularly from 1906 to 1909, for recruiting staff and developing the Wellington laboratory facilities. In 1908 Aston established the first district testing laboratory for export butter at New Plymouth. His work during this early period set the pattern for the application of analytical chemistry to the New Zealand agricultural industry.
On top of his organisational tasks, Aston carried out practical investigations ranging from the isolation of tutin and other poisons from native plants, to the analysis of wheats, dairy products, animal feeds, grasses, soils, fertilisers and limestones. Much of this work was reported in the New Zealand Journal of Agriculture and its extent is indicated by the large number of entries in the cumulative indexes under his name.
Aston's interests focused on plant and animal nutrition in relation to soil conditions. A major concern in the early twentieth century in the volcanic central North Island was 'bush sickness', whereby animals grazing the newly established pasture on pumice land gradually wasted away and died. From about 1905, in conjunction with animal scientists J. A. Gilruth and (later) C. J. Reakes, Aston worked to uncover the cause of this problem. Once it was proved that bush sickness was not a contagious disease he deduced that it was probably traceable to a mineral deficiency in the animal's feed. From studies on the chemical composition of pumice Aston concluded in 1916 that an iron deficiency in the pasture was a likely explanation. He found that heavy dosing of animals with iron salts frequently, but not always, gave relief. In 1931 he advocated the use of limonite salt-licks as a better means of control. The puzzle was completely solved in 1935 when two Australian workers, John Filmer and E. J. Underwood, investigating Aston's use of limonite reported that there was a lack of cobalt, not iron, in the pasture. Limonite contained larger traces of cobalt than did iron salts, hence its greater effectiveness as a remedy.
Although Aston did not discover the ultimate cause of bush sickness, his work led to the solution of the problem. With the development of cobalt licks and cobaltised superphosphate much of the central North Island pumice country was developed, particularly after the Second World War. Aston's greatest achievement was his recognition that a livestock ailment was due to a deficiency of a minor mineral element not in itself required at such levels for pasture growth. In 1927, after Aston's research on bush sickness had received overseas publicity, the Empire Marketing Board initiated an annual grant to the New Zealand government for research on problems of animal nutrition. Aston was appointed to administer the funds and for the next five years an extensive and fruitful programme of research into pasture composition was carried out by the Department of Agriculture.
In addition to his professional interests, Aston was a keen botanist. He made studies of the distributions of native plants, particularly in the mountain ranges of the central North Island, and reported on the flora of the Tararua and Ruahine ranges and Mt Tarawera. He also undertook ecological investigations of Campbell Island and the Auckland Islands, Turakirae Head and various parts of the South Island. Aston helped popularise bush tramping as a recreation. His crossings of the southern Tararuas in association with W. H.Field during 1909–10 were among the earliest by trampers. In 1911 Aston assisted in survey work on Tararua tracks, and when the Tararua Tramping Club was founded in 1919 Field became president and Aston vice president. Aston was also a council member and president of the Forest and Bird Protection Society of New Zealand from 1946 to 1948, and was a member of the Tongariro National Park Board from 1926 to 1937.
As a scientist of high repute, Aston was one of 20 original fellows elected to the New Zealand Institute in 1919. He served on the Board of Governors of the New Zealand Institute and then the Council of the Royal Society of New Zealand from 1915 to 1951 and was president of the institute from 1926 to 1928. In 1925 he was awarded the Hector Memorial Medal and Prize for 'the investigation of New Zealand chemical problems'. He was also a fellow of the Royal Institute of Chemistry and a council member for the New Zealand Institute of Horticulture.
In 1936 Aston retired from the Department of Agriculture. His contribution to New Zealand science was recognised in 1948 when he was made a CBE. Photographs show a short, rather chubby man with a relaxed open face. He was genial and direct, and always had the capacity to inspire his colleagues with enthusiasm. Bernard Aston never married and died in Wellington on 31 May 1951. He was buried at Karori cemetery.