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I guess it's more of an archaeology question, but this is the closest forum I could find.
So, we stopped at Gardiki Castle, Corfu, Greece, built in the late Byzantine era in the 13th century, and walked along it's perimeter since it was all locked up. Some parts were reconstructed, and between them a tower was restored. Within that tower, and some other reconstructed wall parts, there were what seemed to be lead sheets, or, at any rate, there were sheets of a soft metal (deformable by hand with little effort) embedded between the stones. Why is that there? Why haven't I seen it before?

  • What castle and located where? – Rajib Apr 14 '15 at 16:28
  • Corfu, Greece, said to be Byzantine but possibly early Venetian, 13th century A.D. Not sure the exact name of the area, but it is not one of the two major forts of the town, it's further north. – user3079666 Apr 14 '15 at 16:30
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    You may want to edit the information into your question. – Rajib Apr 14 '15 at 16:33
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    Indeed, I also found if on Google maps for visual reference – user3079666 Apr 14 '15 at 16:42
  • This question has received multiple answers; if one of them answered your question, please consider marking it accepted. If not, it would be useful if you indicate what you find missing. – Semaphore Aug 25 '15 at 8:48
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In many cases, during early stone structures throughout the European region, there would be "I" (Capital) shaped groves used to connect stones together (half the "i" shaped grove in each side-by-side block) particularly during difficult portions of construction. In many cases these would be filled with molten lead and this lead link would help secure the stones together.

This is very well explained in the book: Castles: A Short History of Fortifications from 1600 B.C. to A.D. 1600, William Heinemann, Ltd., London/Toronto, 1939.

  • This link pbs.org/wgbh/nova/lostempires/trebuchet/counterweight.html describes the looting of lead roof sheathing for melting into trebuchet counterweights... – DJohnM Apr 14 '15 at 22:05
  • I understand the concept, it was used in antiquity too (in the Parthenon's columns for example I believe), but these were lead sheets, and they were very deformed, pressed between the stones (not connecting them by any means), thus i doubt that is their role.. Unless they were found on sight and the workers had no idea what they were and just forced them between the stones, but still, they seem to be consistently thin, indicating they were flat before being bashed.. – user3079666 Apr 14 '15 at 22:17
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Many medieval buildings had (and still have) roofs made of lead sheets. This was a very reasonable material for roofs, not vulnerable to corrosion. One disadvantage is that it is very heavy. Also this was a common material for all sorts of pipes and gutters and other metal details. Even in modern times (I mean 50 years ago) lead was commonly used for underground cables protection. You do not explain what exactly were the parts you have seen.

On the question why you have not seen this before, I do not have an answer. It is very common.

  • There are accounts of the burning of St Paul's Cathedral during the Great Fire of London, with molten lead from the roof sheathing pouring down the surrounding streets... – DJohnM Apr 14 '15 at 22:02
  • This could explain the origin of the lead, however it does not explain why it is irregularly placed between the rocks. An idea I heard recently suggests it is between the wall parts that were preserved and those reconstructed. I repeat, it is not straight, it's just between the stones, as if separating layers or something, but not even horizontally. – user3079666 Apr 15 '15 at 12:54
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Without seeing a photograph I cannot say for sure, but by far the most likely possibility is that what you are seeing are the remains of what was once a sheeted masonry wall.

In some cases masonry walls were covered with lead or copper sheets as a form of protection. In these cases a groove, called a "raglet", was made in the stone and the sheet of lead inserted into it, then flattened against the wall, and secured the same way on the other side, hammering it in tightly.

The reason why you see only a fragment left in the wall is because a metal scavenger has ripped off the sheeting and sold it for scrap, leaving behind just the strip in the raglet which he could not easily get out.

  • This sounds plausible enough, certainly the best explanation so far! Do you have any links for pages with more info on this? – user3079666 Apr 16 '15 at 9:55
  • No, we are talking about very old processes that were not done very often. In any case masons are not known for being big writers. You could probably fit every book on masonry published in the 20th century onto a shelf 3 feet wide and none of them will discuss sheeted walls because the use of such things died out long before. In fact, you could probably talk to 100 modern masons and not one of them would know what a sheeted wall is. People die and older methods are forgotten. – Tyler Durden Apr 16 '15 at 13:23
  • True... So it's possible that it was applied to a 13th century Byzantine provincial fortification? – user3079666 Apr 16 '15 at 21:46
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In reference to the lead sheets between the Parthenon stones talked about by user3079666 Apr 15 '15 at 12:54, it was common in medieval and ancient masonry to place lead sheets between load bearing stone blocks. The lead would deform to fill the irregularities and evenly distribute the load, keeping the stones from failing due to the load being concentrated at the high spots rather than the entire surface.

I've personally saw lead sheets between load bearing stone blocks next to the main entrance of the Cathedral of St Louis on Bursa Hill (the site of Carthage) near Tunis, Tunisia. The lead was only visible where the edges of the stones had weathered away exposing the lead so I couldn't tell how widely the lead was used.

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