Until 1880 the best and only way to print a stamp was to use a hand-roller printing press like the spider press. While the exact styles and designs have changed over the years, at heart the spider press is a very simple machine that has stood the test of time. Even after more advanced printing methods were invented, like steam and electric powered presses, the spider press was still occasionally called upon to make stamps. It plays a valuable role in the testing process for certain stamps even today.
The spider press uses intaglio printing, which is printing using an engraved plate. While the mechanics of the press and printing like this are simple it takes a lot of skill to get everything exactly right. The teams working the press rarely made errors and printed around three hundred and fifty sheets of one hundred stamps every day.
The spider press is called a spider press because the wheel which pushes the plate and paper through the press consists of extremely long spokes. These spokes remind people of the many legs of a spider.
The first step in intaglio printing is to coat an engraved metal plate in ink. The ink is then wiped off of the plate everywhere but inside the lines of the engraving. The press works by exerting enormous pressure on both the engraved plate and a piece of paper resting on top of it. The pressure is so great that the ink is pushed from the lines of the engraving onto the paper, creating a printed image. The pressure is created when the wheel turns two cylinders, one above the plate and one below, so that the engraved plate and paper are squeezed between them. The long spokes of the wheel create enough leverage that it is relatively easy for a person to create the necessary amount of pressure.
The direct replacement of the spider press was a four-plate steam power-assisted press that could print four plates at a time, four hundred stamps instead of one hundred. It was also automated. It was able to ink plates and even to partially wipe off the ink. It still needed a lot of human supervision though, and had a team of three people working on it at all times. A press team traditionally consisted of a “pressman” who inked the plate and turned the wheel of the press and an assistant, generally a woman, who was in charge of laying and then removing the paper. The person touching the paper had to have clean hands, not ink covered hands from inking the plate, so an assistant was very necessary. The steam powered press had two assistants, one to put paper on and one to take it off.
The spider press was still used to print stamps as late as 1920. In 1918, during World War I, the Bureau of Engraving and Printing was printing so many things that they were using every single press they had, even retired ones like the spider press. That is why the first airmail stamp, the Curtiss Jenny, was printed on a press like this. The stamp featured a blue airplane inside a red frame. This was printed by running the paper through the press twice on two different plates, one for each color. A single sheet of stamps was sold which accidentally featured the blue airplane flying upside down in the red frame. The team working the press had either put the plate on backwards or loaded the paper backwards. This became known as the Inverted Jenny, and the stamps are some of the most famous American stamps in existence.