86521 S5006698

3000

VL

500

10

d

[mm]

5    10    15 Nr 20    25    30    35    ⁴⁰

Fig. 10. Modem fired fine grey jog from Haarhausen Uttrasound wave vetodty (VL). standard deviatk>n of vetodty (»)^and vesse* tadcneoe (c) (after Dobrzańska and Piekarczyk 1999-2000 fig. 6)

tire ultrasonic wave drops to 1550 m/s onJy to flucluate In the further sections. where minor increases and de-creases ot the wave velocity were recorded. The veto-city fluctuations In the adjolning yessefs base areas com-blned with slight changes ot thickness prove the use of the spiral coiling technique.

In the section where the rim of the yessefs base was thickened (pointa 5 and 14) no serlous velocity drop was observed contr a ry to other tested yessels wrth a ring base where a significant drop of the wave vełocrty in the same section was apparent. Gńren the ooiour of the yessefs cross-section, flaking of its surface, as weil as Iow ve-lodties of the ultrasonic wave indicating the artefacfs Iow density, we can assume that the firing temperaturę was relatńrely Iow.

Fine grey ware pot from Kraków Pleszów (Figs. 4. 9).

A fragment of base with a central concavrty (point 13) and a flaked surface was examined. At this point the maximum velocrty of the longitudinal wave propagation was measured (v_Ł = 3900 m/s) representing the point of maximum density (Fig. 9: VL). Velocities of the adjoining areas are lower (c. 3600 m/s) and the yessefs base is the thickest (Fig. 9 d). In the further section (points 7-0 and 17) the greatest drop in the ultrasonic wave vetoaty was obsenred (up to 3250 m/s) and as a resułt this shows the lower density of the vessel's basal thickness. In points 4-6 and 18-21 we can again observe the increase of the ultrasonic wave propagation velocrty with a simufta-neous minor decrease of the yessels basal thickness. A significant yetodty decrease. however. was measured at the point of the highest thickness of the base rim (point 1).

Gńren the characteristic fluctuations of the ultrasonic wave velocities recorded for the adjoining points of dif-ferent thickness, rt can again be assumed that the vessel was fonmed by the spiral coiling technique. In the middle sections of each coil we can obsenre the maximum thickness and the maximum density of the materiał and in con-sequence the increase of the ultrasonic wave vełocity.

Fine grey vessel from Haarhausen (Figs. 5.10).

The maximum vełocrty (v_Ł >2800 m/s) was measured at the vessel's neck (points 2-6 and 32-36) and the minimum at the base (points 13-16 and 22-26) where the yetodty of the ultrasonic wave drops by almost 1000 m/s.

In the centro of the base (points 18-21) the yetodty increases to 2200 m/s (Fig. 10: VL). We can obsenre a sym-metrical distribution of yetodties with reapect to the pofs axis. which is due to the method by which the jug was

formed, having been thrown on a wheel. This is also in-dicated by the symmetrical distribution of wali thickness again with respect to the pofs axis (Fig. 1ty. d).

The maximum density of the materiał was obsenred at the neck. and the minimum yalues were detected in the areas around the base. In the middle of the yessefs base the density of the materia! is higher. the pctoer having appked morę pressure to the day. but sbfl considerabły lower than at the nack. The highest yetodty (density) fluctuations. exceeding 300 m/s, were obsenred in points 2-7 and 32-36 (Dobrzańska. Piekarczyk 1999-2000:97. 98. 102 fig. 2:1; 6).

Condusions

Based on resutts of the anafyses rt can be assumed that Celtic grey podery was produced by a combinabon of the use of the cottng technique combined wrth use of the wheel building. Initially the vessel was buflt up by hand cofls of day in a spiral from the base to the bełły. Then a wheel was used to draw the imtial form upwards in a marne* contrary to the true throwing technique where a whoie vessel • formed from a single lump of day on the wheeł-head.

The abcve condusion can be supported as foHows. First is the ultrasonic tesbng resułt indicating changes in the density of the materiał in the areas adjacent in the yessefs wali Bustrated by changes in the ułlrasonic wave yetocrty. The dńrersrty n wave propagation intensify can be recognised by the high yetodty recorded for the body of the coisof day contrasbng wrth Iow yetodties charac-teristic of the points where the cois bonded Conse quentfy. this drfference is reflected in the thickness of the wal of the pot It is thicker at the coil and thinner at the point of bonding (Figs. 6-9). In contrast to the exami-ned yessels. the modem copy from Haarhausen was thrown on a potter s wheel, which is mdicated by the symmetrical and even wali thickness as wełl as symmetrical disbibubon of yetodties with resped to the yessels ans (Fig. 10).

Pottery techruques can also be successłuDy identi-fied by yarious forms of cracfcs which are dearfy exposed when an intact yessel e sectioned. The cracks oocur most frequentły when the temperaturę of the yessel firing • too high. in such case the pastę of the yessel • less cohesrve. cracks occur at points where the cois bond at particular sections o1 the strudure. Such stres* points are morę dearfy yisibłe on coarse pottery rather than on fine wares and resułt from yariabie pastę composition or the days used. These obcervabons have led to the Identification of coil building combined with use of the wheel