For the first half of the 20th Century, bulk goods were usually bagged and carried in boxcars. After the late 1940’s, covered hoppers greatly simplified the process by allowing the bulk material to be poured in through the roof hatches and dumped out the hopper bays. However, flour, starch, sugar, and plastics do not “flow” easily from a standard hopper bay. To solve this problem, the Fuller Company of Catasauqua, PA, patented the Airslide concept. In an Airslide covered hopper, the bays are formed into two narrow, steep-sided troughs with a layer of air-permeable material at the bottom. Air is pumped through the material causing the lading to fluidize and flow easily through the hopper outlets. General American Transportation, starting in 1953, built the Airslide covered hoppers. One of the two original configurations was a 2,600 cubic foot, single bay car with a 70-ton capacity. In addition to railroad-owned cars, there were a number of Airslide covered hoppers leased by GATC to sugar and bakery companies.
The Canadian Doughnut Company was one of those companies that started out as one thing, producing doughnuts, and ended up doing another, milling flour and supplying it to the bakery industry.