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"A" Mill Explosion

Title: Article Describing Dust Explosions
Type: Newspaper
Date: 1878
Source: Minnesota Historical Society

Description: Many people had theories about the cause of the Washburn "A" Mill explosion. The writer of this magazine article is demonstrating experiments that he had done to prove that flour dust was the cause of the explosion.


I have performed a few experiments, which I will now repeat, which will illustrate to you the immense power that these materials exert when burned in a confined space.

This box (Fig. 2) has a capacity of two cubic feet; the cover has a strip three inches deep nailed around it, so that it telescopes into the box; there is in this lower corner an opening for the nozzle of the bellows, Device for pumping air. in this an opening for the tube to the lamp. I place now a little flour in the corner, light the lamp, and my assistant places the cover upon the box and steps upon it. Take notice that upon blowing through the hole, and filling the box with a cloud of flour, the cover comes up suddenly, man and all, until the hot gas gets a vent, and a stream of fire shoots out in all directions.

Here is a box (Fig. 3) of three cubic feet capacity, including this spout, nine inches square and fifteen inches long, coming form the top of it; at the ends doors are arranged closed like steam-boiler manholes; Openings in mill boilers that allowed for the repair and maintenance. openings for light and bellows are arranged as in the previous box.

Here is a box, weighing six pounds, that will just slip over the spout; it has a rope lest is should strike the wall after the explosion. Placing now the lamp in the box, some dust in the corner, and the box over the spout, we are ready for another explosion. You observe, after blowing vigorously for a second or two, the dust in the box take fire; the box over the spout is shot off, and rises until the rope (about twelve feet long) jerks it back; it strikes the stage with great force, rebounds and clears the foot-lights, and would strike the floor below were it not for the rope.

I have thrown a box similar to this in the open air twenty feet high, while, as we shall see presently, less than an ounce of flour is being consumed.

I have fastened over the top of the spout five thicknesses of news- paper; upon igniting a boxful of dust as before, the paper is thrown violently into the air, accompanied by a loud report as it busts. For the last experiment I have a box of four cubic feet capacity (Fig. 4); five sides are one and a half inch thick, the remaining side one-quarter inch. Upon igniting the dust in this box, filled as in the other cases, the quarter-inch side bursts, and a stream of fire shoots out half-way across the stage.