Ceramic Soluble Salts

This problem is common in many terra cotta materials but can also surface in others.

Ceramic soluble salts.

Barium carbonate can be used to precipitate the salts inside the clay matrix so they do not come to the surface on drying. This terra cotta clay vitrifies here at 1957f cone 03. In high humidity salts become soluble and in low humidity they crystallize. Soluble salt compounds may be introduced into the ceramic pores from ground water agricultural run off seawater or other sources.

When soluble salts are present within the ceramic structure at a percentage considered threatening the conservator must remove them. Soluble salts respond to changes in humidity both high and low. If the ceramic is subjected to cycles of drying and wetting the salt compounds will crystallize and mobilize alternatively producing severe pressures on the ceramic body from within the pores ultimately. Mark goudy and liza riddle are a couple from berkeley california who are blazing a new frontier in ceramic arts with their explorations into the applications of soluble metal salts.

How bad can efflorescence of soluble salts of fired ceramic surfaces be. The water dissolves the salt and draws it out of the ceramic. The most common method of removal is by soaking the ceramic in deionized water for extended periods of time. The changing from soluble to crystallization and back damages the surface of the ceramic because salt crystals are larger than liquid salt and therefore will shrink and expand the ceramic body.