Barbed wire fencing is now manufactured in various patterns. The general process may be outlined briefly as follows: - The wire is made of soft Bessemer or Siemens-Martin steel, and is drawn in the wire mill in the usual way. Galvanizing is done by a continuous process. The coil of wire to be galvanized is placed on a reel. The first end of the wire is led longitudinally through an annealing medium - either red-hot lead or heated fire-brick tubes - of sufficient length to soften the wire. From the annealing furnace, the wire is fed longitudinally through a bath of muriatic acid, which removes the scale, and from the acid, after a thorough washing in water, the wire passes through a bath of spelter, heated slightly above the melting point. After coming from the spelter and being cooled by water, the wire is wound on suitable take-up blocks into finished coils. From 30 to 60 wires are passing simultaneously in parallel lines through this continuous galvanizing apparatus, thus insuring a large output. The galvanizing gives the wire a bright finish and serves to protect it from the corrosive action of the atmosphere.
There is a considerable demand for painted fencing, in the manufacture of which the galvanizing is dispensed with, and the spools of finished barbed wire, as they come from the barbing machine, are submerged in paint and dried. The barbing and twisting together of the two longitudinal strand wires is done by automatic machinery. A brief description of the manufacture of 2 and 4 point Glidden wire is as follows: - Two coils of wire on reels are placed behind the machine, designed to form the main or strand wires of the fence. One of the main wires passes through the machine longitudinally. One or two coils of wire are placed on reels at either side of the machine for making 2 or 4 point wire respectively. These wires are fed into the machine at right angles to the strand wire. At each movement of the feeding mechanism, when fabricating 2 point wire, one cross wire is fed forward. A diagonal cut forms a sharp point on the first end. The wire is again fed forward and instantly wrapped firmly around one strand wire and cut off so as to leave a sharp point on the incoming wire as before, while the bit of pointed wire cut off remains as a double-pointed steel barb attached firmly to the strand wire.
This wire armed with barbs at regular intervals passes on through a guide, where it is met by a second strand wire - a plain wire without barbs. The duplex strand wires are attached to a take-up reel, which is caused to revolve and take up the finished barbed wire simultaneously and in unison with the barbing machine. In this way the strand wires are loosely twisted into a 2-ply strand, armed with barbs projecting at right angles in every direction.
When once started, the operation of barbed wire making is continuous and rapid. The advantage of two strands is the automatic adjustment to changes of temperature. When heat expands the strands, the twist simply loosens without causing a sag, and when cold contracts them, the twist tightens, all without materially altering the relative lengths of the combined wires. A barbed wire machine produces from 2000 to 3000 lb of wire per day of ten hours.
In some American states, the use of barbed wire is regulated by law, but as a rule these laws apply to placing barbed wire on highways. Others prohibit the use of barbed wire fencing to indicate the property line between different owners, unless both agree to its use. In some states the use of barbed wire is prohibited unless it has a top rail of lumber.
Barbed wire is also employed in connexion with "obstacles" in field fortifications, especially in what are known as "high wire entanglements." Pointed stakes or "pickets," 4 ft. high, are planted in rows and secured by ordinary wire to holdfasts or pegs in the ground. Each picket is connected to all around it, top and bottom, by lengths of barbed wire.
In England, where the use of barbed wire has also become common, the Barbed Wire Act 1893 enacted that, where there is on any land adjoining a highway within the county or district of a local authority, a fence which is made with barbed wire (i.e. any wire with spikes or jagged projections), or in which barbed wire has been placed, and where such barbed wire may probably be injurious to persons or animals lawfully using the highway, the local authority may require the occupier of the land to abate the nuisance by serving notice in writing upon him. If the occupier fails to do so within the specified time, the local authority may apply to a court of summary jurisdiction, and such court, if satisfied that the barbed wire is a nuisance, may by summary order direct the occupier to abate it, and on his failure to comply with the order within a reasonable time, the local authority may execute it and recover in a summary manner from the occupier the expenses incurred.