Developments in Ceramic Materials Research

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Dimitris Skarlatos, Tilemachos Zakinthinos and Ioanis Koumanoudis
Table 1. Dimensions of spherical or tubular Vessels (cm)
δ1 1-24 Dmax 30-90 H 10-55
δ΄ 1-20 Δ 6-14 H1 14.5-50
δ 2-11 d 0.4-2 λ 1-10
Δ1 3-16 d’ 0.8-1.5
Figure 6. Vases with rare hole arrangement on its base (a) up, Stone with decorative opening placed on
the vase opening (a) down, Cross sectionsof typical spherical & tubular Greek vases (b) [4].
Spherical vases are either with or without a neck, or they are shaped as a jar, a jug, a pot
or an urn, i.e. they are the ordinary clay vessels of the era. The tubular vases are sometimes
clay pipes (known also as quarter wavelength resonators) and sometimes cylindrical vessels.
It must be noted that in contrast with the Helmholtz resonator whose feature is its resonant
frequency for which the wavelength is considerably greater than its dimensions, the length of
quarter- wavelength resonator assembly has a size that is comparable to the wavelengths on
its resonance [2]. In some churches instead of vases, cavities in the wall were found (see
figure 7b). The cavities in the buildings were either formed during construction, or came from
the combination of a structural cavity and a vase, or a cavity formed and then blanked off
using a perforated slab, for the reduction of the cross section and for decoration.
a b
Figure 7. Resonators in Agios Stefanos, Meteora Greece (a) and Uncovered cavities in the church of St
Nicolas of Platani, Patras, Greece (11 th Century Church). The cavities were partially filled afterwards
(b).