With chemist W Doolan, Kirkpatrick developed 'Kirk's Ginger Ale', which would go on to become the company's flagship product. During the 1930s, Kirkpatrick left Owen Gardener & Sons to work for main competitor, Brisbane bottler 'Tristram's', selling 'Kirk's Ginger Beer' under their brand.
In the 1930s, Kirkpatrick and chemist W Doolan created 'Kirk's Ginger Ale', which became the company's main product. He then left Owen Gardener & Sons to work for a competitor in Brisbane, selling 'Kirk's Ginger Beer' under their brand.