Standards for barbed wire
Standards for barbed wire have been established by the American Society for Testing and Materials. Manufacturers of barbed wire use the tests described in these standards to ensure their customers that they are purchasing a quality product.
One spool of barbed wire out of every 50 is selected for testing and inspection. First the dimensions are measured for accuracy. The diameter of the cable wires and the barbs must not vary more than 0.5 inch (0.13 mm). The barbs must extend at least 0.37 inch (9.5 mm) from the center of the cable. At least 93.5% of the spaces between the barbs must be within 0.74 inch (19 mm) of the desired length. (100% accuracy in barb spacing is impossible due to small movements of the barbs during handling.) A 25-foot (7.6 m) sample of the barbed wire must contain at least 69 barbs if they are spaced 4 inches (10 cm) apart and at least 55 barbs if they are spaced 5 inches (13 cm) apart. The wire on the spool must be at least 1,319 feet (402 m) long.
A strength test is performed on a 4-foot (1.2 m) sample of the barbed wire. The sample is pulled by a measured force until it breaks. It must be able to withstand a force of at least 4,230 newtons.
For galvanized barbed wire, another 4-foot (1.2 m) sample is tested for its zinc coating. The sample is weighed, then the zinc is removed with hydrochloric acid. By weighing the sample again and noting the difference in the two weights, the amount of zinc coating can be determined. A similar procedure is used to measure the zinc coating on the barbs. The minimum weight required varies with the diameter of the cable wires. For the most common diameter (0.097 inch or 2.5 mm), each line wire and each barb must be coated with at least 3.2 ounces (90 g) of zinc per square meter (11 sq ft) for a Class 1 coating or at least 8.6 ounces (245 g) per square meter (11 sq ft) for a Class 3 coating. Standard Grade barbed wire has a Class 1 or a Class 3 coating on the line wires and a Class 1 coating on the barbs. Chain Link Fence Grade barbed wire must have a Class 3 coating on the line wires and the barbs.