Here’s what you’ll learn when you read this story:

• For decades, researchers have been perplexed by the ceramic jars built into recesses in the stone counters of Pompeii’s 150-plus taverns.
• Because studying the jars in detail would require breaking them, questions have lingered about what the jars contained and even how they were made.
• New techniques have allowed researchers to finally shed light on the usage and manufacturing of the embedded jars.

Your local tavern may seem like a very modern part of our contemporary world, but it’s probably not that different from its predecessors from 2,000 years ago. There are roughly 150 taberna establishments—one-room shops typically considered the precursor to the modern tavern—preserved in frozen-in-time Pompeii, and if you walked into one today, you might think it looked pretty familiar. But those ancient taverns still contain plenty of mysteries. In particular, archaeologists have long been puzzled by what ancient Pompeiians put in the ceramic jars embedded in the taverns’ stone counters, where they’ve remained since the eruption of Mount Vesuvius in 79 C.E.

In a new study published in the journal Archaeological Method and Theory, a team of Japanese researchers examined 40 of the jars, many measuring up to three feet tall, from 14 different taverns to better understand just what these ceramic vessels were all about in relation to the daily life of Pompeii nearly 2,000 years ago.

The architectural makeup of the Roman-style taverns or shops makes it physically tricky to investigate the jars, since they’re built directly into the taverns’ stone and concrete counters. There’s no way to remove the jars without breaking them and destroying their archaeological context.

To get around that obstacle, the team employed handheld light scanners to record the interior surfaces of the jars and then created an equation that helped them calculate the axis point of the vessel to form a 3D model. From there, the team could “infer aspects of forming techniques and the use-related behaviors they may encode.”

The researchers found that Pompeii’s manufacturing sector was well-versed in a distinct style of pottery, using a level of standardization during production that took the vessels beyond bespoke creation, but that fell short of mass production.

The authors wrote that the central axis deviation patterns of each vessel are “consistent with slow, continuous, and relatively stable rotation assisted by a wheel.” The slow-turning wheel allowed the potter to keep the jars straight and precise while forming the clay, making it possible to use a wheel and work the clay by hand at the same time to craft the relatively tall ceramic pieces.

Because the jars were made on a potter’s wheel, the team knew their central axis was critical to analyzing them. The team created a mathematical process that simulated slicing the jar into pieces and orienting those pieces around the axis to understand how the jar formed. The team found evidence that the jars were built in sections, with the potter stopping and adding more clay at steady intervals, with each section of the jar showing a slightly different tilt. But the result was still uniform enough for a relatively straight finished product.

Three of the city’s taverns contain jars with the same morphology, dimensions, and axis deviation patterns. “This suggests that even in the production of large, technically demanding jars, artisans with prolonged and systematic training could, under certain conditions, achieve almost standardized technological results,” the authors wrote.

But that’s where much of the standardization stops. Overall, other jars from across Pompeii differ greatly in shape and size, not to mention the wobble patterns in relation to the axis deviation, leading the authors to conclude that the city didn’t have a fully unified production method. They found that throughout the 40 examples in 14 taverns, there was a diversity of vessel types, with cylindrical, globular, and strawberry-shaped forms. One tavern featured two jars near each other with similar shapes, but with differing axis patterns, revealing separate production origins.

Understanding just how the vessels were made—and the diversity of manufacturing styles across Pompeii—answers only one lingering question related to the taverns. Understanding the jars’ function remains a mystery. The city’s taverns were known for selling food and drink, but technically, a taberna is a one-room shop that could have sold any kind of goods. Understanding the jars’ contents from 2,000 years ago is still a difficult prospect.

The jars’ contents probably weren’t liquids, since their location embedded in the counter would have made cleaning tricky, and past studies have suggested the jars contained prepared foods and weren’t simply for storage. While questions remain, the authors believe the new method for identifying the history of the jars may open fresh avenues of discovery. “The method,” they wrote, “moves away from reliance on surface traces and provides a new perspective on ceramic production, craftsmanship, and consumption practices in Roman society.”