The Philistines of Gath were thought to be outliers in the Levant in building with Mesopotamia-style fired bricks. But what baked the bricks at Tell es-Safi wasn’t a kiln
“‘Thou shalt be for fuel to the fire ... thou shalt be no more remembered; for I the Lord have spoken it’” Ezekiel 21:37 Phosphate Bonded Refractory
Tales of divine wrath expressed in fire, or kings burning cities down, are not rare in the Bible. Indeed, evidence suggesting conflagration has been found at several sites, including in ancient Jerusalem, Gezer – and the Philistine city of Gath (aka Tell es-Safi).
However, techniques commonly used in archaeology are limited in their ability to distinguish mud bricks fired in kilns as opposed to mud bricks baked by enemies burning the city down, let alone fired bricks that subsequently experienced secondary heating by arson. Nor are the usual techniques helpful in studying mud bricks heated to low temperatures less than about 500 degrees Celsius (932 degrees Fahrenheit), or in identifying the temperature they experienced.
Now a collaboration of Israeli archaeologists presents archaeomagnetism as a method not only to date ancient ruins but as a way to distinguish mud bricks fired in kilns as opposed to ones burned by mishap or in war.
The archaeologists Yoav Vaknin, Oded Lipschits and Erez Ben-Yosef of Tel Aviv University with geophysicist Ron Shaar of the Hebrew University, Adi Eliyahu Behar of Ariel University and Aren Maeir of Bar-Ilan University demonstrate the method works in an article in PLOS One. And when the technique was applied to a specific building in the Philistine city of Gath (located halfway between Jerusalem and Ashkelon), it changed the narrative of the city’s fate at the hands of Hazael, king of Aram Damascus (II Kings 12:18).
O give me a home
In the beginning, as we abandoned the cave for the external dwelling, there were huts built from reeds, branches, bones – even mammoth tusks. Construction with mud bricks may have only emerged in the Late Neolithic.
Mud bricks were (and still are) made by kneading straw or grasses into mud. Pine needles will do. The thoroughly massaged mélange is put into molds to set. Once set, the raw brick is unmolded and left to dry for days or even weeks, ideally in the shade rather than in direct sunlight because drying too fast causes them to crack.
The snag is that unfired mud bricks are vulnerable to the elements, such as rain. Which explains the latter-day mania for painting the house every Passover, Prof. Maeir jokes – the only way to keep a mud-brick edifice standing for any time is to plaster the walls and if you don’t do that regularly, the bricks revert into a mud bath. Sun-dried brick structures from antiquity have only survived under extraordinary conditions: archaeologists have found a mud -brick village in Israel’s Jordan Valley from 7,200 years ago.
More robust kiln-fired bricks seem to have emerged perhaps around 7,000 years ago, in Mesopotamia and the Far East (later than the advent of kiln-fired pottery). The biblical story about the Tower of Babel even specifically mentions the technique: “And the whole earth was of one language and of one speech. And it came to pass, as they journeyed east, that they found a plain in the land of Shinar; and they dwelt there. And they said one to another: ‘Come, let us make brick, and burn them thoroughly.’ And they had brick for stone” – Genesis, 11:1-3.
The 11th-century sage Rashi interpreted that to mean that the bricks for the Tower of Babel had been fired in kilns.
“Some claim that mud bricks were being fired in the Levant too, including here, as early as the Iron Age or earlier,” Vaknin says. “But most people think brick firing here only began in the Roman period.”
Why might the Mesopotamians have been firing bricks but not we so near by? Because they lived on a low-lying plain watered by the Euphrates and Tigris and had plenty of water and mud, less stone. So they had to fire their bricks to be like stone.
In the rocky Levant, on the other hand, people built using mud brick for ordinary construction and if a harder material was required – for instance, for foundations – they used stone. In most parts of the country, mud brick was the main building material until the Roman period.
In 2011, the claim was made in the Journal of Archaeological Science that a specific wall in Gath, predating the Roman period by centuries, was apparently constructed using fired bricks: “a most unusual occurrence for this time period in the Levant,” the authors (including Maeir) observed. It was part of a structure that collapsed over years following King Hazael’s attack in about 811 B.C.E., they surmised.
The new technique indicates that this wall was not made of fired bricks, and the building it was in did not gently crumble over years following that Aramean assault. The wall was made of sun-dried mud bricks and the building it was in burned down in a single spasm of violence.
“Throughout the Bronze and Iron Ages, the main building material in most parts of the Land of Israel was mud bricks,” stated Lipschits. “This cheap and readily available material was used to build walls in most buildings, sometimes on top of stone foundations. That’s why it’s so important to understand the technology used in making these bricks.”
This enlightenment is based on the ability of the archaeomagnetic technique to discern when mud bricks have been exposed to fairly low heat, below the temperature at which bricks are typically fired.
A word on temperatures. The kiddies’ Lag Ba’omer bonfire can reach 900 degrees Celsius, and big ones even more; ceramics are fired at least at 800 degrees Celsius (and usually higher, though beyond 1,200-1,300 degrees, the clay melts into a puddle). Even early Neolithic kilns are believed to have reached temperatures as high as 900 Celsius degrees or beyond. Wouldn’t a city set ablaze reach even higher temperatures?
Not necessarily. “When a city burns down, the temperature depends on a lot of factors, including the burnable elements,” Vaknin explains. Some archaeologists even suspect that biblical adversaries might have brought their own fuel to the foul city they wished to eradicate, he adds.
Maeir points out that British forces in Afghanistan in the 19th century encountered difficulty in punitively burning down the traditional mud-brick architecture, and learned that the best way to destroy a mud-brick village was to throw explosives into each house. “What we learn is that this image we have – that invaders would capture a city and rampage with torches and whole place would burn down – is a misconception,” Maeir says. “You have to make an effort.” Though a burning town could theoretically have had hot spots, he adds – for example, stores of flammables like olive, oil and grains.
Either way, the temperatures that develop in a burning building are not uniform and are not necessarily that high, Vaknin says. “For instance, a roof made of mud plaster can reach 500-600 degrees or more, while the floor can be less than 200,” he says, pointing out that heat rises.
Other techniques to analyze ancient bricks rely on changes in the mineral composition: some disappear, some are destroyed, others change, all of which happens at specific temperatures. The color of the brick changes, but all this only happens above about 500 degrees Celsius. The archaeomagnetism method isn’t based on changes in mineral composition but on changes in magnetization.
The Earth’s magnetosphere constantly fluctuates in intensity and direction. Mud and clay contain ferromagnetic particles that lie in random directions in mud slurry. The ferromagnetic particles in a sun-dried brick will lie in random directions, their signals canceling each other out, and the brick will have only a weak magnetic signal, if any.
But if the mud is heated, as it cools the iron particles line up like tiny compass needles, all pointing in the direction of the magnetosphere at the moment, and they remain in that orientation forever more.
So if bricks have no magnetic signal to speak of, they were sun-dried. If each brick in an ancient wall has a different magnetic orientation, then evidently they were fired in kilns, each brick fired in whichever orientation vis-à-vis the magnetosphere.
And if the bricks in a wall have the same orientation, they were likely heated together and we may surmise that somebody had an epic accident, or the enemy burned the building down.
Crucially, the new technique enables the archaeologists to detect heating below 500 degrees Celsius, which hadn’t been possible using the spectrometric techniques, Maeir adds.
In Gath, for instance, previous work hadn’t detected fire inside the building to which the wall was associated, but it was there. The lower course of mud bricks was shown to have been heated to less than 400 degrees Celsius and higher bricks (again, heat rises) to 500-600 degrees or so, the archaeologists say.
The new technique was also applied to the rubble by said wall, which had been thought to result from decades of decay following the Aramean conquest. The rubble shared that same magnetic orientation as the bricks in the wall, the team found. And thus they could demonstrate that the collapse happened in one dramatic event.
What about fired bricks in a building that then gets burned by the enemy? Double-firing, as it were – can the technology be helpful there too? “If the fire is hot enough, indeed the original magnetization will be erased and the bricks will gain the orientation of the newest conflagration,” Vaknin explains. That is why reconstruction of temperature is key. If a brick demonstrated to have been fired is then found to have been heated to, say, 400 degrees,which is too low for a kiln – we have separate burning events.
And yes, a brick could have been sun-dried, then placed in a structure that was burned down by an invader, and then that could have happened again.
Anyway, all this depends on knowing the magnetic field. How much does the ambient planetary magnetic field change over time? How often? What resolution can be achieved?
Well, we don’t know any of that exactly; research is ongoing, but for now it can be said that if the magnetic signal is statistically different at two sites, then evidently they were not destroyed in the same military campaign. If they have the same signal, they may have been destroyed in the same military campaign, Vaknin says.
So what have we? A technique that can help not only date ancient sites using the magnetic properties of clay pots and bricks, and that can detect the temperature of the heat they experienced, but which ended up changing the narrative of the ferocity of Hazael’s attack on Gath, based on the story of one house. A house that had been thought not to have burned inside, only on the roof, but it did. That house had been thought to have been, strangely, made of fired bricks, but wasn’t; and it didn't collapse over time but abruptly, in one terrible event that left scars in the collective memory:
Concrete Refractory “Then Hazael king of Aram went up, and fought against Gath” – 2 Kings 12:18.