A QUANTITATIVE METHOD TO DESCRIBE THE SHAPE OF CONTAINER WALLS GEDIMINAS VAITKEVIČIUS (Institute of Lithuanian history) (g.pontifinas@gmail.com)
Ø220
Ø89
67°
Lip 52°
Shoulders
12°
Neck
20° 9
Ø3
57°
58°
Ø25
3
RΘ 47°
A method for describing the morphology of ceramic vessels using quantitative parameters. A description using quantitative parameters is more accurate, detailed, and less subjective than a qualitative description. This method was used to compile a typology of 13th–17th-century ceramic vessels from Vilnius: first the shape was recorded in 3D format, then the profiles were quantitatively measured and defined using an AutoCad and the Desmos programmes. ● The description is based on the premise that these vessels were tools used for cooking, transport, storage, etc. Their shape would have been adapted to their function and so each vessel was investigated as a functional system. According to this premise, a vessel was seen as a construct; its shape being thus divided into modules that were measured separately (Fig. 1): Rθ (part below the Ømax); the shoulder; the neck; and the lip. ● Each module’s profile consists of an aggregate of straight, regular arc, and irregular arc segments, the former two being described by their geometric dimensions: length + angle; diameter + arc length (in degrees) + angle (Fig. 1), the latter by trigonometric equations: tangentoids (Fig. 2: a, b, c, d) and parabolas (Fig. 2: e, f). Up until now, the description of an irregular arc has posed a technical problem, which prevented the use of quantitative parameters in the description and typology of ceramics. It was solved with the advent of the Desmos programme which made it possible to describe irregular arc segments by equating them with trigonometric graphs. ● Each point on a vessel profile described in this manner has its own unique coordinates and the profiles of diverse vessels become quantitatively comparable. The descriptive measurements achieved using this method are more precise than the variances in the profile at different cross-section locations on the same vessel. ● Conclusions: The use of quantitative parameters in describing a shape minimizes the subjective factor (descriptions made by different archaeologists who perceive and evaluate the same artefact differently now even coinciding); This method unifies the system for describing diverse vessels; Vessel typology becomes based on quantitative parameters instead of weakly defined qualitative concepts or even impression-based associations. Mathematical modelling techniques can be used to evaluate the practical properties of vessel shapes, as is done in engineering and technical design, which opens up a wide field of research in investigating aspects of instrumental evolution.
°
119
Δ1,45
Fig. 1 regular arc segments Δ – the deviation between vessel’s profile and the descriptive arc
Fig. 2 irregular arc segments: tangentoids a, b, c, d, parabolas e, f. Δ – the deviation between vessel’s profile and the tangentoids.