Digital Print History - The Siphon Recorder: The 145-year-old Inkjet Printer

Lord KelvinThe siphon recorder was invented by William Thomson and patented in 1867, long before the 1980’s when inkjets were first used to create digital prints from a desktop computer.

The siphon recorder was developed specifically as a way to capture the very weak signals that were being received through the extremely long trans-ocean telegraph cables. These signals were not strong enough to pull down the standard metal sounders that were used with landlines (and made the famous tap, tap, tap sound we are so familiar with from western movies). The trans-ocean signal sending units were also different than traditional telegraph senders. These did not have a single handle to tap out the dots and dashes of Morse code but double handles. One sent a positive charge and the other a negative charge.

In the receiving unit, the siphon recorder, a glass tube (the siphon) oscillated back and forth on a pivot. It swung in one direction when the signal was positively charged (representing the “dot”) and the other direction with the negative charge signal (representing the “dash”). The upper end of the tube was immersed in an ink reservoir; the lower end held just above (but not in contact with) the recording paper. The ink was charged and was pulled in a spray from the tip of the tube by an oppositely charged plate behind the recording paper. As the paper moved forward and the tube swung back and forth, it created a continuous “wobbly” line. The fluctuation of the line, therefore, corresponded with the source’s transmitted signal and could be read back from Morse code into the originating language.

Example of Syphon Recorder Printout

So there is a good argument for the claim that this device was indeed the first inkjet printer. It actually functioned more like the early continuous inkjet printers (such as from Iris Graphics) as opposed to the more common drop-on-demand printers we now find in homes and offices around the world. In modern, drop-on-demand printers the ink is only ejected from the nozzle when the computer data calls for it. The siphon recorder, on the other hand had a constant stream of ink flowing from the glass tube. In continuous inkjet printers the ink flows constantly as well, however, the ink can be diverted to a “trap” when areas of the image require no or low ink levels. The siphon recorder did not have this ability; its ink was always being jetted onto the paper. However, because the siphon recorder only needed to draw a single uninterrupted line, this was not a problem.

The first demonstration of the power of the siphon recorder was in London on June 23, 1870 when it was used to capture the weak signals that came to London from Bombay, India. In the July 9, 1870 issue of the British magazine Punch a poem satirizing the event included the lines:

  • What have they met to accomplish, these leaders of fashion and science?
  • What is it brings them together, before the small syphon that, waving,
  • Scatters its fine jet of ink in accord with the pulses electric,
  • So making plain to the eye what the spark through the wire is conveying;

In the 1950’s the Siemens-Elema Company used a similar design to create an inkjet printer for recording signals from medical devices such as an electro-cardiogram (ECG). It is important to note that while both of these devices were inkjet printers, they were not digital. They recorded analog signals. It would be several more decades before digital inkjet printing would make its way onto the desktop.

William Thomson was knighted in 1866 at Windsor castle by Queen Victoria and named Baron Kelvin of Largs in 1892. Lord Kelvin passed away on December 17th, 1907 and was buried in Westminster Abbey next to Sir Isaac Newton.



  • Thompson, Silvanus P. The Life of Lord Kelvin, Chelsea Publishing Company, New York, NY, 1976
  • Pond, Stephan F. Inkjet Technology and Product Development Strategies, Torrey Pines Research, Carlsbad, CA, 2000