Factors affecting ceramic composition:

Cultural factors:

Paste recipes for different wares and vessel functions.

Paste preparation (sorting, sifting, refining, mixing clays, adding temper).

Firing temperature.


Post-depositional factors:

Contamination from ground water and pollutants.

Weathering (hydration) of exposed surfaces.

Natural factors:

Parent material mineralogy for both clay and aplastic (mineral) inclusions.

Clay formation processes: erosion, redeposition; sorting of size fractions.

Weathering of clay horizons and loss of mobile cations.


Clays are widely distributed across the landscape, and often display clinal or continuous variation in composition, making it difficult to distinguish closely spaced clay sources.

Clays are naturally variable, creating greater element diversity within ceramics from same clay source.

Cultural manipulation may obscure or enhance signature of natural clays.

Post-depositional contamination may generate noise in data.

Several of these factors potentially confound the Provenance Principle.

Oregon State University Archaeometry Lab