It is “Black Friday” after all! These distinctive covered hoppers have roamed the rails since the 1930s. The typically black covered hoppers are anything but boring. And while they can be found all across North America, with their low numbers and specific commodities if you’re not along a route they normally frequent they would be easy to miss altogether.
What Is Carbon Black?
Generally speaking, carbon black is a variety of amorphous carbon. It can be made in several different ways. Most is made by the incomplete combustion of hydrocarbons in a furnace (furnace black). It can also be produced through thermal cracking of natural gas (thermal black) or incomplete combustion of acetylene (acetylene black).
Carbon blacks are used in a variety of products. The majority are used in making tires. When added to rubber, carbon black increases strength and resistance to abrasion. It is also used for inks and paints, wire insulation and other rubber products. Acetylene black is electrically conductive and used in dry cells and explosives.
Produced at about 20 different plants across the United States and Canada by a handful of companies, the product tends to move in small shipments (one or two carloads) to specific customers over routine routes. If you happen to be near, or along the route to one of these producers or consumers then you’ll see these cars regularly. Otherwise, you’ll have to look hard to find one.
Carbon Black Cars
What differenciates a carbon black car from a “standard” covered hopper? Like most commodities, covered hoppers are customized to meet the needs of the carbon black industry. Aside from the obvious black color chosen for most paint schemes (a concession to the weathering effects) carbon black cars usually have several other things in common:
- Cars typically have three relatively small 16″ butterfly outlets on the bottom of the car for unloading.
- Roof hatches are also typically small, 8″ or 16″ and found in greater numbers than typical larger hatches
- Sampling spigots on the car sides
Cars have been built to a variety of capacities and designs but 77 ton capy. cars are most common. ACF, Darby Car, GATX, Magor, National Steel Car, Pressed Steel, Procor, Pullman-Standard and Thrall have each built cars. The cars were generally built in small quantities and there were many subtle differences between runs and not-so-subtle differences between builders.
While these cars may not be frequent sights on the rails, once you’re aware of them it is fun to start taking pictures and comparing notes. You can watch trains for years and not see two exactly the same! Keep your eyes open as you go train watching, you never know when one of these black snowflakes will show up.