In 1871 Johnston married Elizabeth Lawson, daughter of George Lawson, a confectioner and baker based in Newington; together they had thirteen children. Johnston worked in and managed his Canongate shop until around 1874 when a major business opportunity arose with the French Government. Following the disastrous defeat of the French forces by the Germans during the Franco-Prussian War of 1870-71, the French military authorities were convinced that greater, sustained nutrition for their troops would have led to a better outcome and so commissioned Johnston to investigate the possibilities of concentrated beef provisions. He set off for Canada, with his wife, and two sons, in late 1873 or early 1874.
The Johnston family settled in Sherbrooke in the Province of Quebec where John established a large factory and set about fulfilling his business obligation to the French. In order to maximise profits, Johnston also used the factory to can other foods, such as tomatoes, as well as exploring the potential of developing ‘Johnston’s Fluid Beef’ for the public at large.
In what Johnston himself called “…one of those fortunate coincidences,” the ‘Scott Act’ was introduced in Canada in 1878 -temperance legislation greatly limiting the sale of alcohol – which Johnston realised left the people of Canada in search of an “innocuous stimulant” and which they eventually found in his ‘Fluid Beef’ drink. Johnston seized the opportunity and concentrated his efforts on promotion, which perhaps marked the rise of his invention from the obscurity of his early experiments in the Canongate butcher’s shop to worldwide prominence as a household commodity
A further phase in the product’s growth in popularity occurred within a year or two of this good fortune for Johnston. After a fire in his Sherbrooke factory in 1879, John relocated to a larger factory in Montreal. Here, he discovered the great Montreal winter carnivals where he was one of a number of enterprising individuals erecting huge ice palaces; he secured the monopoly of the interior of one such ice building. He installed a colossal urn, “ten feet high and 12 feet in circumference, placed over a great stove, which, strange to say, produced no effect whatever on the ice walls of the palace”. This huge vessel was able to serve over 75,000 people with his hot beverage over the 10-day festival, an event which Johnston saw as the real beginnings of commercial success for his ‘Fluid Beef’ drink- soon to be renamed Bovril.