Many readers were probably fans of watching Myth Busters, that television show that used scientific recreation to test urban and historical legends, each one more bizarre than the last. Well, in episode 29, aired in March 2005, they “busted” one of those out-of-place artifacts often cited by conspiracy theorists and lovers of the esoteric to support the existence of extraterrestrial civilizations or human societies predating our current one: what is known as the Baghdad battery.

This artifact is often presented as “evidence” of the alleged use of electricity in antiquity, alongside the famous light bulb of the Egyptian temple of Dendera and the Coso artifact. In the first one pareidolia makes people see a lamp where there is nothing more than a lotus flower with a snake inside, resting on a Djed (a pillar symbolizing Osiris’s backbone). Meanwhile, the second is simply a spark plug encased in hardened clay, which some claim to be half a million years old despite proof that it was manufactured in the 1920s.

The Baghdad batteries—plural because three were found—are somewhat different from such crude interpretations, although archaeologists reject the proposal that they functioned as voltaic cells used in electroplating.

bagdad batteries antiquity
One of the reliefs in the crypt of the Dendera temple, with the supposed “light bulb”. Credit: Olaf Tausch / Wikimedia Commons

To clarify, a voltaic or galvanic cell is a device designed to generate electricity from chemical reactions, essentially consisting of two metals separated by a porous membrane but connected through a saline bridge.

In the specific case of the Baghdad batteries, we are talking about terracotta jars measuring 14 centimeters in height with an opening of nearly four centimeters. Inside, attached to the mouth with a layer of bitumen, is a copper sheet rolled around an iron rod measuring nine centimeters in length and two and a half in diameter. The upper part of this rod protrudes by a centimeter and shows traces of having been insulated from the copper with a lead wrapping. Internal corrosion suggests that the jar may have contained some type of unidentified acidic organic substance.

The discovery took place in 1936, by workers from the Iraqi State Railways Department, on a hill in Kujut Rabua, a village southeast of Baghdad, in an old tomb they had just unearthed. The site is located not far from the ancient city of Ctesiphon, on the banks of the Tigris River, which, although abandoned after Baghdad was founded nearby, had once been the capital of the Parthian and Sassanian empires. This is why the jars have been dated to one of those periods, though no exact date has been determined.

bagdad batteries antiquity
Diagram of the Baghdad battery. Credit: Chatsam / Wikimedia Commons

It was the Austrian Wilhelm König, then director of the Laboratory of the Baghdad State Museum, who proposed the hypothesis that these objects were batteries probably used for therapeutic purposes, specifically electrotherapy.

König, who was actually a painter rather than an archaeologist, believed they were from the Parthian period, which spanned from 250 BCE to 224 CE (although stylistically, they would align more closely with the Sassanian period, from 224 to 651 CE). In 1940, he returned to Europe due to illness and published Im verlorenen Paradies. Neun Jahre Irak (“In the Lost Paradise: Nine Years in Iraq”).

In that work, he described how he experimented by introducing an electrolyte into the jar and connecting the assembly to a lamp, which faintly lit up. Encouraged by this, he linked the recovered pieces to similar artifacts found in other Mesopotamian regions. Three of them appeared in 1930 during an excavation campaign led by American archaeologist Leroy Waterman in Seleucia. They dated to the Sassanian period (5th and 6th centuries CE) and consisted of clay jars containing bronze cylinders wrapped in pressed papyrus, inside which there were iron and bronze rods affixed to the bottom.

bagdad batteries antiquity
Modern reconstruction of the Baghdad batteries. Credit: Boynton / Flickr

The following year, a German-American expedition led by Ernst Kühnel discovered six more such containers in Ctesiphon, some with bronze cylinders and two with lead plates, all corroded due to a decomposed organic coating. In König’s opinion, if all these jars were connected, it would be possible to generate a practical voltage. In fact, he attributed the Baghdad batteries to a galvanization process that produced the thin layer of gold coating on silver instruments preserved in the Iraqi museum, thus providing another possible practical application of the invention in its time.

That line of speculation was continued after World War II by Willard Gray, an engineer at the American company General Electric, who created a replica of a vessel and filled it with what experts claimed was missing from the original, having evaporated over time: an electrolyte that would generate current due to the potential difference between the metallic electrodes.

To be precise, he used copper sulfate, while clarifying that in antiquity, they might have used grape juice, for example (in Myth Busters, they used lemon juice). This allowed him to generate two volts of electricity and, within a couple of hours, give a golden patina to a silver figurine he had placed inside.

bagdad batteries antiquity
Reconstruction of the rods and the copper cylinder. Credit: Tympanus / Wikimedia Commons

In 1978, the German Egyptologist Arne Eggebrecht, former director of the Roemer-und Pelizaeus-Museum in Hildesheim, Germany, claimed that he had also reproduced this electroplating process using vinegar as an electrolyte, successfully gilding another figurine. However, he neither documented it in writing nor took photographic evidence.

Meanwhile, W. Jansen experimented with different and unconventional electrolytes, such as vinegar and benzoquinone (an organic compound derived from benzene that some beetle species can produce), asserting that he had achieved satisfactory results.

However, archaeologists and scientists almost unanimously criticize all these experiments because they tend to suffer from the same flaw: insufficient, nonexistent, or inadequate documentation of the process. Gray’s case, for instance, is now considered fraudulent because, as he described it, he could not have generated more than ten amperes—far too little to gild a figurine in two hours. At a minimum, he would have needed ten days of uninterrupted work to accumulate just a few grams of silver.

bagdad batteries antiquity
Another modern recreation of the vessels. Credit: libby rosof / Daniel Petraitis / Flickr

The Baghdad batteries would have needed to contain an electrolyte and be connected in series with wire to achieve the necessary power, but these additional components have never been found. Likewise, despite claims to the contrary, no one has ever seen an ancient gilded figurine produced by this method. Archaeologists clarify that the ones in the Iraqi museum were fire-gilded with mercury, a technique used in antiquity alongside conventional gold plating. In Myth Busters, each of the ten replicas they made of the vessel generated half a volt; all of them had to be connected together to surpass four volts.

The list of objections to the galvanic hypothesis continues with the case of Eggebrecht, whose reliability has already been questioned. Beyond the lack of documentation, there is suspicion that he used a modern electrolyte rather than vinegar, for two reasons: first, vinegar would not have provided sufficient power; second, after just over a year of such intense use, the iron rods would have been nearly disintegrated or severely degraded (yet, as seen in the original pieces, they have survived intact to this day).

Furthermore, other factors challenge the idea of electrical use. The rod protrudes from the vessel’s opening, but the cylinder does not, and it was also covered with bitumen, making it impossible to connect a wire to complete a circuit. Additionally, bitumen is thermoplastic and therefore unsuitable, as a battery of this nature would require frequent refilling with electrolyte fluid for prolonged use—something necessary for it to be practical.

bagdad batteries antiquity
Facade of the National Museum of Iraq, now restored after the war. Credit: Hussein A. Al-mukhtar / Wikimedia Commons

Other critiques extend to a broader field, questioning the documentary contextualization of the original excavation, which was flawed and debatable since it was not carried out by archaeologists but by railway workers. However, the most significant issue today is that we no longer have the vessels, meaning that modern reconstructions are based on dubious written descriptions rather than actual models. And why have they not been preserved? Because of the looting of the National Museum of Baghdad in 2003, at the end of the U.S. invasion of Iraq. Only old black-and-white photographs remain.

In conclusion, it is not impossible that the Baghdad batteries, assuming they had the missing elements (electrolyte, wire), could have generated a small electric current that would have likely been astonishing in its time. However, it would have been so weak that finding a practical application is difficult—except for the unprovable speculation of a medical use, possibly for treating arthritic pain in a manner similar to electroacupuncture (regardless of its therapeutic effectiveness).

Nevertheless, most archaeologists do not support this theory and instead lean toward a more mundane purpose: simple containers, perhaps for scrolls or some cosmetic product—both of which could have caused the corrosive acidity detected inside the vessel.

This article was first published on our Spanish Edition on September 1, 2023: Las controvertidas vasijas de Bagdad, que algunos consideran baterías voltaicas creadas durante la Antigüedad

SOURCES

Kenneth L. Feder, Frauds, myths, and mysteries. Science and pseudoscience in archaeology

Alberto Granados, ¿Es eso cierto? Fraudes, errores, experimentos inauditos… todas las respuestas sobre el mundo científico

Carlos Javier Taranilla de la Varga, Enigmas y misterios de la Historia

Wikipedia, Batería de Bagdad

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