Above: Multicolored ABS filament rolls are the plastic "ink" used by most consumer 3D printers.Image Credit: Rick Pollack/FlickrMost consumer 3D printers use “ink” made of colored plastic line. But despite the self-reliant and Earth-friendly bent of many 3D printing hobbyists, it’s surprisingly difficult to find 3D printing line, or filament, that’s made of recycled plastic — despite the fact that the type of plastic used, known as ABS plastic, is easily recyclable from old plastic bottles.