Furnace Project 2019

Roman shell-shaped vessels

The Borg Furnace Project 2019 was primarily devoted to identifying possible production techniques for Roman shell-shaped vessels.
These vessels appear in the form of bowls or bottles with a base and are characterised by prominent, clearly rounded ribs.
They belong to the category of mould-blown vessels, which means they were produced by blowing a lump of hot glass into a mould.


Experiment 1

In Experiment 1, glass was blown into two mussel shells using a blowpipe (Image 1). This produced a clear but rather angular and flat impression.
Subsequent impressions produced with the same shells became progressively less distinct due to their contours wearing away because of the heat.


Experiment 2

In Experiment 2, glass was blown into a two-part ceramic mould produced from a direct impression of the exterior of a shell (Image 2).
The shell’s uneven surface was reproduced on the glass vessel, which appears considerably rougher than the originals and lacks their smoothness.


Experiment 3

In Experiment 3, glass was blown into a freely shaped ceramic mould, which again consisted of two parts (Image 3).
The vessel produced with this method had clearly rounded ribs on an otherwise smooth surface and thus most closely resembles the Roman originals.


Findings and update

The experiment was able to demonstrate that Roman glassmakers used freely shaped ceramic moulds to produce shell-shaped vessels.
However, a recently found Roman shell-shaped glass bottle was probably produced using Process 2.

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