Corso Piazzarolo

The piazzarolo is the worker who lends his work in a salt pan or in an alum quarry. The double sulphate of aluminum and potassium dodecahydrate or potassium-alum better known as potassium alum and rock alum is a mixed salt of aluminum and potassium of sulfuric acid and at room temperature it appears as a colorless and odorless solid. Since ancient times it was used to wash wounds and in numerous productive activities and in various sectors. In the textile industries it was used as a fixative for colors, its use was therefore basic in the dyeing of wool, in the realization of miniatures on parchment and in the tanning of leathers. It was then used for the production of glass and in medicine it was used as a hemostatic. Rock alum is useful in the painting technique of watercolor to soak the paper before working with the colors, the surface treated in this way is more uniform and, by absorbing less color, it intensifies the pictorial stain effect typical of this technique. Alums have been known since ancient times for their astringent properties and were used as a mordant to dye wool, to embalm animals and human bodies, and to make wood fireproof. These substances were actually minerals containing alum and mixtures of alum and green vitriol.