174 ARCHAEOLOGICALILLUSTRATION
radius scale maintaining the same orientation until the
outer curve coincides exactly with one of the curves of
the radius chart when viewed from above. If the rim
fragment fits the curve of, for example, 10 cm radius, it
can be deduced that the vessel was 20 cm wide at the rim,
despite the fact that only one piece of the rim remains.
The dimensions of the vessel can now be indicated on
the drawing.
Once the dimensions of the rim or base are established,
the outline of the sides of the vessel can be drawn. This
can be done by using a block as described above, but great
care must be taken to make sure that the piece of pottery
is orientated correctly. Position the pot rim or base
against the vertical wooden block, ensuring the rim is in
its correct plane (as when using the radius chart). When
isolated sherds are being drawn, they should be orientated
to provide the maximum complete profile, although the
angle at which this profile is orientated may have to be
estimated to a degree. Plasticine or modelling clay can be
used to stop the pot or sherd from moving. Use an engin-
eer’s set square as described previously.
Figure 18.3 The shape of an object can be recorded by
establishing a vertical datum (here a plastic set-square on
a wooden base) and taking offset measurements. (Photo:
Edward Martin)
Figure 18.4 The diameter of sherds can be determined by
the use of radius templates. (Photo: Edward Martin)Figure 18.5 A chart on which circles of measured radii are
drawn allows rim or base potsherds to be aligned with suc-
cessive curves until an exact fit is found. Segments that show
the percentages of the full circle enable the amount of the
fragment being measured to be assessed. (Photo: Edward
Martin)