Fig. 4

Calcium phytate main treatment steps: (1) humidification, gradual transition from a dry to a wet state to minimize dimensional tensions in the object; (2) washing in water, for removal of acids and soluble transition metal ions such as Fe²⁺ or Cu⁺; (3) immersion in calcium phytate solution, complexation of Fe²⁺ and Fe³⁺ by phytate; (4) deacidification with calcium bicarbonate, neutralization of remaining acids and deposition of an alkaline reserve in the paper; (5) sizing with gelatine, increasing the mechanical strength of paper and adding a protective layer between the atmosphere and the surface of the ink; and (6) local mending to support areas with mechanical damages and prevent further losses