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sabre') between the two types ofmortar is still visible where thc ccntral ١ower uscd

to be bound to the islamic cnceinte. Four samplcs have bccn aalyscd giving thie
following results‫ ﺩ‬:

Wter soluble salts N. W. S.w. Ccntral s.E.
Silica sand Bastion Bastion 'owcr
Carbonate sand + lime Bastion
Gypsunm ٦.2 6.9 2.1
15.6 ١5.9 32.6 7.4
60.8 55.1 5.28 38.2
13.9 15.8 40.1
.91 11.2

Once again, clearly, we are dealing with a gypsumllime mix. In this case,
however, microscopic examination has revealed the presence of gypsun fibers
which indicates that Calcium sulphate re-crystalized in the mortar. his phe­
nomenon would suggest that gypsum was not introduced in the mix as an inert
charge, but as an active binder. Yet, a Calcium Sulphate content ranging from 9 to
.15 per cent is far too little for gypsum to be the only binder material: the utilisation
of a predominant quantity of lime, therefore, has to be assumed. As a matter of
fact, the lime proportion cannot be accurately estimated, the carbonate sand being
chemically identical to aged limel'; nevertheless, it seems highly probable that
gypsum and lime were intentionally mixed.

As for the greyish colpur of this mortar, an ancient technique, widely spread in
the Middle East, may be explanatory: in his study on traditional crafts, Wulff
states that "a specially water-proofed mortar is prepared by mixing sand, lime, and
wood ashes?5, his can be easily achieved if the lumps of quick lime are extracted
from the kiln with the remaining coals and ashes and subsequently soaked together
inwater. he presence of large carbon fragments in the samples examined accounts
for this hypothesis.

A‫ﻡ‬AD FOR
he masons who, in the ifrst half of XVII century, mied the mortars for the

building of Arad fort were apparently less meticulous than their earlier colleagues:
in the eight samples analysed, in fact, the gypsum content varies from 7% to
47%٦.

Most probably, the gypsiferous soils that provided the raw material were very
impure and the mineral, not homogeneously fired, yielded an imprecise mixture of
gypsum, lime and even a sort of cement if significant clay was presentl٩, his mix

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