A breakthrough achieved by researchers from 4 Israeli universities — Tel Aviv College, The Hebrew College of Jerusalem, Bar-Ilan College and Ariel College- will allow archaeologists to establish burnt supplies found in excavations and estimate their firing temperatures. Making use of their technique to findings from historical Gath (Inform es-Safi in central Israel), the researchers validated the Biblical account: “About this time Hazael King of Aram went up and attacked Gath and captured it. Then he turned to assault Jerusalem” (2 Kings 12, 18). They clarify that in contrast to earlier strategies, the brand new approach can decide whether or not a sure merchandise (corresponding to a mud brick) underwent a firing occasion even at comparatively low temperatures, from 200°C and up. This info might be essential for accurately deciphering the findings.
The multidisciplinary examine was led by Dr. Yoav Vaknin from the Sonia & Marco Nadler Institute of Archaeology, Entin College of Humanities, at Tel Aviv College, and the Palaeomagnetic Laboratory at The Hebrew College. Different contributors included: Prof. Ron Shaar from the Institute of Earth Sciences at The Hebrew College, Prof. Erez Ben-Yosef and Prof. Oded Lipschits from the Sonia & Marco Nadler Institute of Archaeology at Tel Aviv College, Prof. Aren Maeir from the Martin (Szusz) Division of Land of Israel Research and Archaeology at Bar-Ilan College and Dr. Adi Eliyahu Beharfrom the Division of Land of Israel Research and Archaeology and the Division of Chemical Sciences at Ariel College. The paper has been printed within the scientific journal PLOS ONE.
Prof. Lipschits: “All through the Bronze and Iron Ages the primary constructing materials in most elements of the Land of Israel was mud bricks. This low cost and available materials was used to construct partitions in most buildings, typically on high of stone foundations. That is why it is so vital to know the expertise utilized in making these bricks.”
Dr. Vaknin provides: “Throughout the identical period dwellers of different lands, corresponding to Mesopotamia the place stone was exhausting to return by, would fireplace mud bricks in kilns to extend their energy and sturdiness. This method is talked about within the story of the Tower of Babel within the Guide of Genesis: “They stated one to a different, Come, allow us to make bricks and fireplace them totally. In order that they used brick for stone”(Genesis 11, 3). Most researchers, nevertheless, imagine that this expertise didn’t attain the Land of Israel till a lot later, with the Roman conquest. Till that point the inhabitants used sun-dried mud bricks. Thus, when bricks are present in an archaeological excavation, a number of questions should be requested: First, have the bricks been fired, and if that’s the case, had been they fired in a kiln previous to development or in situ, in a harmful conflagration occasion? Our technique can present conclusive solutions.”
The brand new technique depends on measuring the magnetic subject recorded and ‘locked’ within the brick because it burned and cooled down. Dr. Vaknin: “The clay from which the bricks had been made comprises thousands and thousands of ferromagnetic particles — minerals with magnetic properties that behave like so many tiny ‘compasses’ or magnets. In a sun-dried mud brick the orientation of those magnets is sort of random, in order that they cancel out each other. Due to this fact, the general magnetic sign of the brick is weak and never uniform. Heating to 200°C or extra, as occurs in a hearth, releases the magnetic alerts of those magnetic particles and, statistically, they have a tendency to align with the earth’s magnetic subject at that particular time and place. When the brick cools down, these magnetic alerts stay locked of their new place and the brick attains a robust and uniformly oriented magnetic subject, which might be measured with a magnetometer. It is a clear indication that the brick has, in actual fact, been fired.
Within the second stage of the process, the researchers regularly ‘erase’ the brick’s magnetic subject, utilizing a course of referred to as thermal demagnetization. This entails heating the brick in a particular oven in a palaeomagnetic laboratory that neutralizes the earth’s magnetic subject. The warmth releases the magnetic alerts, which as soon as once more prepare themselves randomly, canceling one another out, and the entire magnetic sign turns into weak and loses its orientation.
Dr. Vaknin: “We conduct the method regularly. At first, we warmth the pattern to a temperature of 100°C, which releases the alerts of solely a small proportion of the magnetic minerals. We then cool it down and measure the remaining magnetic sign. We then repeat the process at temperatures of 150°C, 200°C, and so forth, continuing in small steps, as much as 700°C. On this approach the brick’s magnetic subject is regularly erased. The temperature at which the sign of every mineral is ‘unlocked’ is roughly the identical because the temperature at which it was initially ‘locked’, and finally, the temperature at which the magnetic subject is absolutely erased was reached through the unique fireplace.”
The researchers examined the approach within the laboratory: they fired mud bricks beneath managed circumstances of temperature and magnetic subject, measured every brick’s acquired magnetic subject, then regularly erased it. They discovered that the bricks had been fully demagnetized on the temperature at which that they had been burned — proving that the tactic works.
Dr. Vaknin: “Our method allows figuring out burning which occurred at a lot decrease temperatures than every other technique. Most strategies used for figuring out burnt bricks are primarily based on precise modifications within the minerals, which often happen at temperatures increased than 500°C — when some minerals are transformed into others.”
Dr. Eliyahu Behar: “One of many widespread strategies for figuring out mineralogical modifications in clay (the primary part of mud bricks) resulting from publicity to excessive temperatures relies on modifications within the absorption of infrared radiation by the varied minerals. On this examine we used this technique as a further instrument to confirm the outcomes of the magnetic technique.” Dr. Vaknin: “Our technique is rather more delicate than others as a result of it targets modifications within the depth and orientation of the magnetic sign, which happen at a lot decrease temperatures. We are able to start to detect modifications within the magnetic sign at temperatures as little as 100°C, and from 200°C and up the findings are conclusive.”
As well as, the tactic can decide the orientation by which the bricks cooled down. Dr. Vaknin: “When a brick is fired in a kiln earlier than development, it information the course of the earth’s magnetic subject at that particular time and place. In Israel this implies north and downward. However when builders take bricks from a kiln and construct a wall, they lay them in random orientations, thus randomizing the recorded alerts. Then again, when a wall is burned in-situ, as may occur when it’s destroyed by an enemy, the magnetic fields of all bricks are locked in the identical orientation.”
After proving the tactic’s validity, the researchers utilized it to a selected archaeological dispute: was a selected brick construction found at Inform es-Safi — recognized because the Philistine metropolis of Gath, residence of Goliath — constructed of pre-fired bricks or burned on location? The prevalent speculation, primarily based on the Outdated Testomony, historic sources, and Carbon-14 relationship attributes the destruction of the construction to the devastation of Gath by Hazael, King of Aram Damascus, round 830 BCE. Nevertheless, a earlier paper by researchers together with Prof. Maeir, head of the Inform es-Safi excavations, proposed that the constructing had not burned down, however moderately collapsed over many years, and that the fired bricks discovered within the construction had been fired in a kiln previous to development. If this speculation had been right, this may be the earliest occasion of brick-firing expertise found within the Land of Israel.
To settle the dispute, the present analysis workforce utilized the brand new technique to samples from the wall at Inform es-Safi and the collapsed particles discovered beside it. The findings had been conclusive: the magnetic fields of all bricks and collapsed particles displayed the identical orientation — north and downwards. Dr. Vaknin: “Our findings signify that the bricks burned and cooled down in-situ, proper the place they had been discovered, specifically in a conflagration within the construction itself, which collapsed inside just a few hours. Had the bricks been fired in a kiln after which laid within the wall, their magnetic orientations would have been random. Furthermore, had the construction collapsed over time, not in a single fireplace occasion, the collapsed particles would have displayed random magnetic orientations. We imagine that the primary cause for our colleagues’ mistaken interpretation was their incapability to establish burning at temperatures under 500°C. Since warmth rises, supplies on the backside of the constructing burned at comparatively low temperatures, under 400°C, and consequently the previous examine didn’t establish them as burnt — resulting in the conclusion that the constructing had not been destroyed by fireplace. On the similar time, bricks in higher elements of the wall, the place temperatures had been a lot increased, underwent mineralogical modifications and had been due to this fact recognized as burnt — main the researchers to conclude that that they had been fired in a kiln previous to development. Our technique allowed us to find out that every one bricks in each the wall and particles had burned through the conflagration: these on the backside burned at comparatively low temperatures, and those who had been present in increased layers or had fallen from the highest -at temperatures increased than 600°C.”
Prof. Maeir: “Our findings are crucial for deciphering the depth of the fireplace and scope of destruction at Gath, the biggest and strongest metropolis within the Land of Israel on the time, in addition to understanding the constructing strategies prevailing in that period. It is vital to overview conclusions from earlier research, and typically even refute former interpretations, even when they got here from your individual college.” Prof. Ben-Yosef provides: “Past their historic and archaeological significance, historical constructing strategies additionally had substantial ecological implications. The brick firing expertise requires huge portions of combustive supplies, and in historical occasions this might need led to huge deforestation and even lack of tree species within the space. For instance, sure species of timber and shrubs exploited by the traditional copper trade within the Timna Valley haven’t recovered to today and the trade itself finally collapsed as soon as it had used up its pure fuels. Our findings point out that the brick firing expertise was most likely not practiced within the Land of Israel within the occasions of the Kings of Judah and Israel.”
