- Poster Session
POTTERY MANUFACTURING TECHNIQUES: ULTRASONIC TESTING OF THE WHEEL-MADE POTTERY (ROMAN PERIOD)
Halina Dobrzanska and Jan Piekarczyk
The results of studies
of pottery production techniques are the main sources of information
enabling the determination of the technological level of ceramic production
and contribute toward discussions about tradition and innovation in
pottery making.
This poster presents an attempt to use ultrasonic testing in studies
involving the manufacturing techniques of Roman wheel-made pottery from
southern Poland. Ultrasonic testing of materials and objects is based
on measuring the velocity of wave propagation in elastic bodies. Velocity
is a function of microstructure, elastic constants, density and geometric
dimensions of an examined material. The microstructure of a material
(i.e. the phase composition, arrangement of phases, grains and pores,
heterogeneous density) determines the heterogeneity as well as anisotropic
mechanical properties of material. Heterogeneity in an object is a result
of an uneven distribution (different density) of material, while anisotropy
is caused by a privileged arrangement of phases, elongated grains and
pores. These values are affected by the phase composition, method of
paste preparation, forming techniques and firing process. The areas
of heterogeneity in an object, their size and anisotropy can be easily
determined with ultrasonic methods, which is regarded as non-destructive
but time consuming testing.
Ultrasonic waves were sent through the thickness of the vessel wall
at points distributed on a line running along the height and the base
of the vessel. When the ultrasonic wave is sent through the adjoining
areas of the sample characterised by a different material density (different
porosity), different velocities of the ultrasonic wave are measured.
The distribution of density in a sample can be determined in a non-destructive
way by examing the distribution of velocities on its surface. On this
premise rests ultrasonic testing of ceramic objects.
The distribution of cracks in the examined vessels and the asymmetrical
distribution of velocity along with macroscopic observations of the
walls inside and outside the vessels enable determination of their production
techniques. The vessels were produced using the coiling technique combined
with the wheel.
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