Gunpowder Manufacture

The following illustrated article was in the The Graphic of 24 Oct 1874 and while it does not describe the working of our local gunpowder mills it is a good narrative account of the processes involved in gunpowder manufacture.

THE MANUFACTURE AND TRANSPORT OF GUNPOWDER

As considerable interest has been excited in the manufacture of gunpowder, and its transport, we this week illustrate [as reproduced at the foot of this article] the whole process of manufacturing gunpowder, by sketches which our artist has made by the kind permission of Messrs. Pigou, Wilks, and Laurence at their mills at Dartford.

Gunpowder is composed of three ingredients, charcoal, sulphur, and saltpetre, incorporated with each other in the relative proportion of about 13, 11, and 76, in a powdered state. Great care has to be exercised in obtaining the right kind of charcoal, as also in purifying the sulphur.

“Giving up Matches at the Entrance” explains itself.

Our next illustration shows the grinding of the sulphur and the charcoal, which are reduced to a fine powder. This is carefully sifted into a “dusting reel” to remove any vestiges of grit or impurity which might otherwise find their way into the powder, and cause an accident in the course of the subsequent stages of the manufacture. Saltpetre, also, when not refined on the premises, is subjected to the same process.

Our next sketch shows the “Incorporating Mills,” where the composition, having been roughly mixed in the proper proportions, is incorporated by being ground, in a wet state, under edge runners, each weighing from four to six tons. This grinding is continued for a longer or shorter time, according to the quality of the gunpowder to be produced. This process is somewhat dangerous, and it is this which most frequently causes those minor explosions to the sound of which all persons residing near gunpowder mills are more or less accustomed. The powder thus completely pulverised leaves the mill in small lumps. Being too friable to be conveniently granulated it is therefore taken to the “Hydraulic Press” and pressed between copper sheets by hydraulic power until it is sufficiently hard to bear the granulating process without crumbling to dust.

Next we come to the “Corning” or “Granulating House,” where the cakes of powder from the hydraulic press are broken into grains by being passed between brass rollers, the grains being sorted into different sizes by falling over sieves which are set at a pretty steep incline, and kept shaking in order to free their meshes from the grains.

In our next illustration we are still in the “Corning” House, where “Hand Sifting” is going on. In cases where it is desirable to obtain a very carefully sized powder, the grains are again sifted, this time by hand, in circular sieves placed on a frame fixed to a revolving shaft having a crank at the point where it passes through the frame.

The next process is the “Glazing,” or giving a polish to the grains, by causing them to revolve for some hours in closed barrels containing three or four cwt. each, a small quantity of black lead being added when a very high degree of polish is required, as in the case of blasting powder, which is intended to be used in damp localities. After being polished the powder is dried in a stove, warmed by steam or hot water pipes. The final process before weighing the powder into barrels is the “Dusting,” or removing any fine particles of powder which may still adhere to the surface of the grains. This is accomplished by passing the powder over sloping sieves if ‘‘large,”or through hollow cloth cylinders if “small grain.” In the Packing House the powder is weighed into parcels under five pounds each, and packed into tin canisters for the “sporting” trade.

The “Expense Magazine” is a store-house for gunpowder before it has undergone the final process, if there is any reason to delay the completion of the manufacture. It is built in the water, and is provided with a lightning conductor. The “Charge House” is also surrounded with water, and has a water tank on the roof. Here the finished powder is stored in bags on shelves, about a foot from the ground. So much for the manufacture of gunpowder, but we may add that all people connected with the works, and any one entering them, have to be “shod” with large leather shoes, with nails of copper, lest a spark from an unwary heel might fire the powder charged air. All the bearings of the machinery are also of copper.

As regards the transport of powder, much has been said of late respecting the terrible and culpable negligence of Canal and Railway Companies, who treat it with the same nonchalance they would display towards barrels of pickled pork. At these works, however, the utmost precautions are taken, the whole internal carriage, from the time the powder leaves the incorporating mills until it is ready to be sent away, is conducted by boats or barges, each sufficiently small to be propelled by one man with a punt pole at a speed of about two miles an hour. These boats are, of course, kept entirely for powder work. For the shipping trade the powder has to be carted to a spot in Dartford Creek, not far from its entrance to the Thames. It is there transferred to barges which proceed to the spots in the Thames where the authorities permit powder to be shipped.

For the home trade, the powder is carted direct from Dartford to the railway or canal which will carry it to its destination. We may conclude our remarks by stating that, according to law, it is forbidden to carry more than 25 lbs. by land, or 200 lbs, by water at the same time, and that any one smoking on board a vessel laden with powder is subject to a fine of 5/-. Any person delaying the loading or unloading can be fined 10/-, while no vessel proceeding above Blackwall is allowed to carry more than 25 lbs. weight of gunpowder.

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