PHYTATE - A POTENTIAL CONSERVATION AGENT FOR THE TREATMENT OF INK CORROSION CAUSED BY IRONGALL INKS

Ink corrosion, the degradation of paper by irongall inks, destroys paper manuscripts and pen drawings. The degradation can be attributed to both acid hydrolysis and iron (II)-catalyzed oxidation of cellulose. Phytic acid, a natural antioxidant, blocks the latter process. its action has been investigated by simulating ink corrosion with accelerated aging tests at 90 degrees C and a relative humidity, cycling each 3 hours between 35% and 80%. Mechanical strength was tested with a bursting tester at screen patterns, made with an irongall ink of a composition representative of old ink recipes. When ink corrosion occurred, the aged paper samples burst at the patterns. By deacidification with an aqueous solution of magnesium bicarbonate, the half-life of the bursting strength increased from 6 to 15 days. In combination with a treatment with an aqueous solution of sodium phytate, the half-life increased to 23 days. Surface pH values of both treated sets were similar. Therefore, the increase in stability must be due to the antioxidant function of phytate. Further research should lead to practical phytate-based conservation treatments of manuscripts and pen drawings threatened by ink corrosion.