A brief history of degaussing

Here at Varese, we’ve talked about degaussers rather a lot. (Anyone would think we sell the things!) But it occurs to me that many people are unfamiliar with what degaussing actually is. There’s a lot more to it besides removing data from hard drives. This week, I’d like to take a brief look at the history of degaussing, from a child prodigy of the 1700s to an electromagnetic arms race to the many present-day applications of a big magnet.

Gauss in the house

Our story starts in 1777 with the birth of Carl Friedrich Gauss (“gauss” rhymes with “mouse”, in case you were wondering). You may not have heard of him, but Gauss is sometimes known as the “Princeps mathematicorum”, or “the greatest mathematician since antiquity”. Gauss demonstrated a keen mathematical ability from the age of three, and throughout his teenage years he made numerous groundbreaking discoveries in modular arithmetic. After completing “Disquisitiones Arithmeticae” in 1798 (a number theory textbook written in Latin – a bit of light reading for you there), Gauss turned his attention to other fields such as astronomy, geometry, and of course, magnetism. In 1831, he devised a unit to neatly represent magnetism by mass, charge and time – creatively named the gauss unit.

Wartime woes

Fast-forward to World War II. The crafty Germans developed magnetised naval mines, which could detect the magnetic field of ships passing overhead. These mines played havoc with the British fleet, until Commander Charles F. Goodeve and his crack team of scientists devised a novel solution. By installing electromagnetic coils in the ships, the magnetic field could be counteracted to avoid triggering the mines. Carl Gauss was German, so the Germans used the gauss unit to measure magnetism. Commander Goodeve’s process of electromagnetic reversal thus came to be known as “de-gaussing”! Installing these coils proved to be quite expensive, so the Brits took to dragging a big electromagnetic cable over their ships to wipe out any residual magnetism instead. The US Navy also commissioned their own fleet of specialised degaussing ships. Eventually, the Germans improved their magnetic mines, leading to a cat-and-mouse game of increasingly sophisticated electromagnetics.

Modern applications

In modern times, degaussing is used for two primary purposes – clearing up cloudy CRT screens, and erasing magnetically stored data. Do you recall when switching on a CRT television or computer monitor, you’d hear a thump or a humming sound? A key component of CRT screens, the sinisterly-named “shadow mask”, is responsible for directing electrons onto the grille to create fancy pictures. This shadow mask can be affected by external magnetic fields, throwing off its aim and causing discolouration on the screen. The sound you’d hear turning on a CRT is actually a built-in degaussing coil, trying to fix these magnetism issues. Unfortunately the built-in coils would weaken over time, requiring a more powerful external degausser to clear up cloudy screens.

The other modern purpose of degaussing, as we never tire of talking about, is erasing data from hard drives and tapes. Since this data is stored magnetically, a strong degaussing coil can scramble the “magnetic domains” – the tiny magnetised areas on a hard disk platter – rendering data unreadable. A 21st-century drive degausser is little more than a box with a powerful coil in it. Simply insert a hard drive, wait for the thump (much like with those CRT monitors) and voila, no more data. Take a look around our website if you’d like to know more about how this process works and why it’s so useful.

So there you have it! From its humble mathematical origins, to its contribution to the war effort, to unscrambling the latest episode of Eastenders – degaussing has come a long way, and it’s no less useful now than it’s ever been.