Grains of Salt: Evaluating Parameters of pH Measurements for Aqueous Treatments in Paper Conservation

This study investigates the difficulty paper conservators often have in obtaining consistent pH measurements of aqueous treatment solutions. The research compares different methods of pH measurement (strips and meters) and the addition of different salt concentrations and types to aqueous treatment solution samples to increase their ion concentration for pH measurement. It also investigates the impact of adding salt to common aqueous treatment solutions (calcium hydroxide and ammonium hydroxide) on pH measurement. While the addition of salt was stabilizing for deionized water measurements, it did not have a consistent stabilizing effect on calcium and ammonium hydroxide adjusted solutions. The unbuffered nature of hydroxide solutions used in paper conservation may be a contributing factor in this inconsistency.