The Challenge of Preservation

Hohokam pot deteriorating in the storeroom
Surface insecurity on the Hohokam vessels was noted for the first time in 1984. Note the large areas of surface powdering, design loss, visible salt crystals, and powder deposits on the metal shelving below the pots. It is suspected that very high humidity during the monsoon seasons of 1983 and 1984 alternating with dry low humidity in the winters, first activated the deterioration process.

Human effigy vessels deteriorating in the storeroom
Soluble salt damage can begin as a bloom (efflorescence) on the surface of a ceramic. As the salt crystals accumulate they obliterate and erase the decorative surface around the pot’s entire circumference, and rings of clay dust accumulate on the shelves below. Soluble salts may result from the clays and technology used in manufacturing a pot, the uses or depositional history of the piece, and/or the conditions under which it is stored or displayed. Thus, not all pots have a soluble salt problem.

Thousands of priceless ceramic vessels are deteriorating on the shelves of the Arizona State Museum due to inadequate environmental controls and storage conditions. Crowded rooms and wild fluctuations in the relative humidity inside the buildings are to blame for the ongoing deterioration of the ancient and historic ceramic vessel collection.

Display of pots damaged by environmental conditions Soluble salts naturally occur in many of the clays used to make vessels, as well as in the soils in which archaeologists excavate them. When soluble salt efflorescence occurs in a ceramic vessel, tiny salt crystals form. With moisture, they grow larger and push apart the ceramic structure while they move to the surface. There they slowly obliterate the decoration while leaving rings of clay dust on the shelves.

The Museum's climate-control problems have been extensively studied and temporary solutions have been attempted. For example, portable dehumidifiers are used each summer to minimize humidity fluctuations in storage areas. Unfortunately these measures are inadequate and the deterioration process continues.

Saving Southwest Traditions: The Pottery Project is a multi-year proposal to stabilize the ceramic vessels and bring the entire collection together in a publicly visible climate controlled room, and to provide custom archival supports in state-of-the-art museum furniture.

View selected pots from this section in 3-D

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Image credits:
Human effigy vessels deteriorating in the storeroom (2000) - Ken Matesich
Display of pots damaged by environmental conditions (2002) - Gary Mackender
Hohokam pot deteriorating in the storeroom (2000) - Ken Matesich