Sand temper

Heidke, J. M. and E. J. Miksa (2000), Correspondence and discriminant analyses of sand and sand temper compositions, Archaeometry 42, 273-299. 

Samples of the different dry clays were taken, as well as those of the prepared mix, the sand tempers, the salt, and the fired pottery. Samples were also obtained from a neighboring potter who followed the same procedure but obtained his clays from a different location. 

When the results of the yellow limestone clay and the red field clay analyses were processed by the potstat routine (10), an average of data from the two clays yielded a pattern that matched (except for sodium) the analytical pattern of pottery made of a mix of the two clays. In the first case, the two raw clays were simply ground and analyzed separately in the second case, the two clays were mixed in a water bath, sand and Dead Sea salt were added, a vessel was formed, dried, and fired, and this finished product was analyzed. The sand temper did not contribute significantly to the relative test element concentrations, but the salt addition did, of course, raise the sodium concentration. These results are graphed in Figure 2. 

In the trace-element data, the first principal component accounts for over 50% of the variance. Aluminum and most other elements correlate positively with the first principal component, a pattern consistent with simple dilution (22,23) - in this case, by quartz sand temper. In contrast, the second principal component (accounting for an additional 15% of the variance) represents the heavy mineral sand component (Ti, Hf, Zr), which negatively covaries with cobalt, manganese, antimony, and arsenic. The Qo and Qm clays from the lowlands are broadly similar in composition (Figure 5). The Qc deposit differs significantly, i.e., the low PC2 scores indicate high concentrations of the characteristic of heavy mineral sands (Ti, Hf, Zr). The Qk and Tp samples span range of composition, but are represented by only 2 samples each. 

The petrographic microscope examination revealed that the black sand temper in the clay was not volcanic ash, but a glass, possibly obsidian particles. Because obsidian sources are relatively few, geographically restricted to the vicinity of modem... 

Coal, bituminous, fines, sluggish 22 Sand, tempered foundry 24... 

S = sand-cast P = permanent-mold-cast other = temper designations. 

Clearly, aeolian processes were much more important at that time than at present. Large parts of the present temperate zone, from the cover sands of the Netherlands to the sand dunes in north-east Siberia are Ice Age (aeolian) sands. South and east of this cover sand belt lies a belt of loess deposits, extending from France, across Belgium, the southern Netherlands, Germany and large parts of Eastern Europe into the vast steppes of Russia, and further east to Siberia and China. A similar east-west loess belt exists in the USA and less extensive areas occur on the Southern Hemisphere, e.g. in the Argentinean pampas. 

Two substrate materials were used for most of the measurements. They were chosen as representative of two types of environmental material found in actual fallout. The first was a clay loam occurring in the Berkeley Hills, Calif. This is a more-or-less typical example of a silicate soil found in extensive areas in the temperate zones. The second material used was a calcium ferrite. This material has been observed in fallout resulting from nuclear explosions at the Pacific Proving Grounds where large amounts of calcium oxide, derived from the coral sand, and iron oxide, derived from towers, barges, or other structures, have been fused together. 

Temper may affect the Sc/Fe ratios if the material used contains these elements in high concentrations and in a ratio much different from the clay. The three sands tested however showed nearly the same Sc/Fe correlation as the red field clays in the region where they were obtained. 

Figure 16. Marshall stability vs. compaction temper-ature—limestone sand...

In Table 3, susceptibility to weathering increases down the list as fewer silicon-oxygen bonds need to be broken to release silicate. Consequently, quartz and feldspars especially, but also mica in temperate soils, are common inherited minerals in the coarse particle size fractions of soil (the silt and sand fractions, 0.002-2 mm). The amphiboles, pyroxenes, and olivine are much more easily weathered. Thus, soils derived from parent material with rock containing a predominance of framework silicates e.g. granite, sandstone) tend to be more sandy, while those derived from rocks containing the more easily weathered minerals tend to be more clayey. 

Pottery is produced by the conversion of sedimentary clay (produced by the weathering of rocks) into hard rocklike objects. The clay minerals, which were formed by the chemical decomposition of certain rock-forming minerals, contain trace elements. The sediments in which these clays are found, however, also contain fragments of the primary minerals from the parent rock (including grains of silica sand). These detrital components, which result from the physical and chemical breakdown of minerals, are often accompanied by authigenic minerals that are chemically precipitated from aqueous solutions. In some ceramics, additional components were added as temper during production. 

---