Why the Roman stonemasons changed the order of the slabs in the marble bookmatch in a villa in Ephesus

A bookmatching is when, in a sequence of slabs (usually from the same block), those with even numbers are flipped. Then the structures in the stone suddenly bump into each other.

In our main article about the villa in Terrace House 2 in the ancient city of Ephesos, we described the marble bookmatch. There is an irregularity in the laying of the stone slabs there – we show here what probably was the problem and how the stonemasons solved it at that time.

A bookmatch as shown results when slabs are cut from a block and placed so that those with even numbers are rotated.

The order of the slabs in the whole bookmatch is then 1-2 / 3-4 / 5-6.

This is how almost the entire base in Terrace House 2 is designed. But on the south side of the wall the order of the plates is changed: it starts here with 1-2 and then continues with 5-4 and 7-6.

The reason, according to the findings of the research group led by Professor Cees Passchier, is that apparently plate 3 was broken during polishing and had to be replaced.

Now, when polishing, if one of the slabs breaks (in this case, the number 3), you can turn back the following slabs and insert an additional slab from the right. However, this did not happen with Terrace House 2 in Ephesos.

However, the problem thus created could have been solved more simply, namely by simply turning the following plates 4-5 and 6 backwards again and then adding plate 7 from the outside. Thus: 1-2 / 4-5 / 6-7.

But why did the Romans not do this, but chose the – more complicated – sequence 1-2 / 5-4 / 7-6?

The Roman stonemasons preferred to change the order of the pairs of slabs. The reason was probably to avoid polishing the slabs on 2 sides, which would make them dangerously thin.

The reason becomes obvious when one considers the (presumed) working method of the polishers:
* before they began their work, they first laid the slabs side by side as they would appear in the base. Then the polishing began, probably on all the plates at the same time due to time constraints.
* but if then an already completely or only partially polished plate broke (in this case: number 3), they could not simply take out the broken plate and turn the following ones backwards and add an additional plate from the right. Because: if you started polishing the plates on both sides, the risk became high that you would fall below a critical thickness and some plate would break. After all, even with polishing only on one side, they are only about 15 mm thick – and this with this marble, which is known to crack readily.
* the Romans found a better way by interchanging the following pairs of slabs.

This did lose a little of the perfect symmetry they were aiming for. But this minor loss of aesthetic impact was acceptable given the fact that the risk of breakage, and therefore cost, was significantly reduced.

Graphic: Cees Passchier

Part of the reconstructed plinth in the Roman villa in Ephesos.

(30.07.2021, USA: 07.30.2021)