Farmers tend to have steady nerves, but Richard Buckley of Taranaki, New Zealand, stands out. When his trousers exploded one day in August 1933, he calmly threw them out of the window onto the lawn. It probably helped that he wasn’t wearing them at the time. A few months later, another Taranaki farmer was on horseback when his pants started smouldering. Around the same time, a Southland family watched, horrified, as their drying laundry started to scorch on the line.
The exploding trousers of 1930s New Zealand were the result of an equation that started with expensive sheep, and took in deforestation, alien invaders, labour shortages and bad chemistry along the way.
New Zealand is famous for having more sheep than people (the current ratio is six to one). But sheep are tricky: you need a lot of them, and they need space. In the 1920s and 1930s, many farmers ran small dairy herds instead. This was the case in Taranaki and Southland, where farms were small operations with grazing land hacked out of dense, wet forest. Sheep hated it, but cows thrived.
But newly-cleared pastureland is attractive to weeds. In 1930s New Zealand, this meant ragwort. Ragwort is poisonous — sheep tolerate it, but cows are vulnerable. New Zealand’s dairy farmers, finding the bright yellow weed fringing their farms, had to get rid of it. Theproblem was, their farms–usually one or two-man operations–were too cash-strapped to hire extra workers, making clearing ragwort by hand impossible.
The solution was to spray it with sodium chlorate, a cheap and effective weedkiller. One drawback, which farmers didn’t know about in advance, was that it reacted with organic fibres like cotton and wool. Another disadvantage: it was very, very flammable.
After spraying, farmers’ clothing would be covered in dried sodium chlorate, which didn’t wash out easily. It would stick, reacting gently with the cotton or wool until friction, heat or open flame kicked off combustion and sent them up in smoke. The best you could hope for, it seemed, was that you weren’t in your pants when this happened.
Once farmers put two and two together, they stopped using sodium chlorate. Ragwort won this one: while cinnabar moth caterpillars are now used as a biological control method, ragwort is still so widespread in New Zealand that farmers occasionally resort to spraying it by helicopter.
For this article I drew on James Watson’s IgNobel Prize-winning article “The Significance of Richard Buckley’s Exploding Trousers: Reflections on an Aspect of Technological Change in New Zealand Dairy Farming between the World Wars,” published in Agricultural History, 78, 3, 2004.