Juha Kallas

Juha Kallas was born in Tallinn on 18 January 1941. His father, Johannes Kallas, was a lifelong confectioner and his mother, Hilja Kallas, a bookkeeper. He later suggested that his Finnish-sounding first name, perhaps shortened from those of his grandfather Johan and his father Johannes, had foretold the two decades he would spend at Finnish universities. A brother, Rein, was born in 1949 and a sister, Meeli, in 1952. He grew up in Nõmme, and his earliest memory was of sheltering in a cellar during the Soviet bombing of Tallinn in March 1944.

He attended Tallinn School No. 27 (now Rahumäe Basic School) from 1948 to 1955 and Tallinn Secondary School No. 7 (now the French Lyceum) from 1955 to 1959. As a teenager he played competitive tennis at the Nõmme sports school, reaching good placings in the Estonian youth class. He enrolled at Tallinn Polytechnic Institute almost by chance, after a school friend suggested they both apply to study chemistry, and graduated in 1964 in the chemical technology of silicates. Under Soviet rules of the time, he spent his first 16 months of study working days as a repair fitter at the Männiku building materials plant while attending lectures in the evenings.

After graduating he was assigned to the Tallinn jewellery factory, where he worked as a foreman and technologist from 1965 to 1968, and then spent a year as a senior engineer at the Estonian SSR ministry of the building materials industry. In 1968 he became a postgraduate student under Professor Enno Siirde at Tallinn Polytechnic Institute, testing a German paper on steam distillation over three years of experiments and theory. He defended his candidate of technical sciences degree in 1972.

In the 1970s he worked in the institute's department of automation, where a research group led by Olav Aarna applied mathematical models to oil shale processing at Kohtla-Järve and Kiviõli. The two men shared the Estonian Komsomol science prize in 1974. In 1976 and 1977 he spent ten months in Professor Harri Norden's chemical engineering laboratory at Helsinki University of Technology. He returned to the chemical faculty in 1979 as a docent, and in 1985 defended his doctor of technical sciences dissertation on the theory and calculation of steam distillation at the USSR Academy of Sciences Institute of General and Inorganic Chemistry in Moscow. From 1986 to 1992 he was professor and head of the department of chemical industry processes and apparatus.

From 1991 he worked at Lappeenranta University of Technology in Finland as a senior assistant, researcher, docent and acting professor, and in 2003 he was appointed professor of separation technology, a post he held until the end of 2008. He was also a professor at Helsinki University of Technology in 1998 and 1999 and taught courses there for more than a decade. He returned to Tallinn as professor of chemical engineering from 1995 to 2000 and later as a senior researcher in the laboratory of inorganic materials from 2004 to 2018.

His research covered the theoretical foundations of chemical and environmental engineering, process modelling, heat and mass transfer, the properties of multicomponent systems, distillation, crystallisation, adsorption, membrane processes and water and air purification technologies. In later years he worked on extracting value from oil shale ash. He supervised many master's and doctoral theses in Estonia and Finland and sat on the editorial board of the Proceedings of the Estonian Academy of Sciences.

Kallas met his wife, Hilja, while working at the Tallinn jewellery factory; they married in February 1967. They had two daughters, Ilona and Kaire. By the time of his 70th birthday in 2011 he had several grandchildren and was already a great grandfather. He lived in Saku, near Tallinn, and remained a keen tennis player throughout his life, including in the Tallinn Technical University staff team and as a partner of colleagues in Lappeenranta. He estimated that he made several hundred journeys between Tallinn and Lappeenranta, using them to read articles and mark theses.

Juha Kallas died on 20 October 2026, aged 85. His death was announced the same day by his family in a notice in Postimees describing him as a beloved father, grandfather and great grandfather. Former classmates from his student years at Tallinn Polytechnic Institute also published a notice of condolence. The cause of death was not made public. A farewell service was arranged for 23 October 2026 at the Memoris funeral home on Valdeku Street in Tallinn.

Kallas was one of the Estonian engineers who kept scientific links with Finland alive across the end of the Soviet era and helped bring modern computational methods into chemical engineering research in Tallinn. His colleague Rein Kuusik credited his arrival in TalTech's inorganic materials laboratory with giving a decisive push to the use of modern software for simulating chemical processes there. His contributions were recognised with the Mente et Manu medal of Tallinn Technical University in 1991, the university's gold badge in 1994 and a share of the Estonian national science prize in 2001. A full bibliography of his publications was issued by the TalTech library for his 70th birthday in 2011.