Room-Temperature Study of Iron Gall Ink Impregnated Paper Degradation under Various Oxygen and Humidity Conditions: Time-Dependent Monitoring by Viscosity and X-ray Absorption Near-Edge Spectrometry Measurements

Abstract

Many western manuscripts were written using iron gall inks. These inks can damage the paper via two major mechanisms: (a) acid hydrolysis, enhanced by humidity, and (b) oxidative depolymerization provoked by the presence of oxygen and free iron(II) ions. The degradation of unsized Whatman paper impregnated with different combinations of iron sulfate, gallic acid, and gum arabic was studied at room temperature in order to assess the relative importance of each mechanism. The samples were stored in various environments including a dry and/or an oxygen-free atmosphere. The cellulose depolymerization was monitored by viscometry and related to changes in the oxidation state of iron, determined by X-ray absorption near-edge spectrometry. The results indicate that residual amounts of oxygen (less than 0.1%) promote cellulose depolymerization, whereas the level of relative humidity has no impact. The cellulose depolymerization also appears closely correlated to oxidative mechanisms. Regarding the oxidation of iron, it only occurs in the simultaneous presence of oxygen and moisture, suggesting the occurrence of rustlike oxidative mechanisms. Finally, the presence of gallic acid has a strong influence, which is only partially explained by its capacity to reduce iron(III) to iron(II).

Application of Arrhenius law to DP and zero-span tensile strength measurements taken on iron gall ink impregnated papers: relevance of artificial ageing protocols

“…Anyway, whatever the cause of acidity, the low pH values of our samples give substantial reasons to suspect acid-catalysed hydrolysis as the main cause of chain scission. This first interpretation does not stand when examining paper behaviour in further details: in previous work [26], ink impregnated papers were conditioned in anoxia and their degradation was delayed. Moreover, papers impregnated with pure gallic acid did not show significant depolymerization at ambient temperature despite showing a low pH value (3.6).…”

“…In a previous work, using anoxic and aerated ageing conditions, we showed that the combination of oxygen and iron was a key factor for cellulose chain breaking occurring in acidic conditions (pH 3-4) [26]. Therefore, paper degradation induced by IGI would be predominantly driven by oxidative mechanisms involving iron or cellulose.…”

“…Three model ink solutions were prepared with different concentrations of these products, chosen according to criteria already largely described in a previous work [26]. All solutions were stirred for 3 days in closed vessels, and then, paper sheets (Whatman No 1, 10 cm large square) were immersed for 10 min.…”

“…Another relevant information gained from our abovementioned work [26] lies in the fact that cellulose depolymerization was sufficiently fast to be measured at room temperature. This point is quite unusual as most kinetic studies on paper degradation involve artificial ageing protocols using relatively high temperatures [10].…”

Light and anoxia fading of Prussian blue dyed textiles

“…For instance, they participate to the oxidative degradation of cellulose [20,21] and increase the concentration of hydroxyl radical generated upon light exposure [18]. As well, iron influences the degradation of cellulose in iron gall-ink manuscripts [22]. Therefore, the participation of Prussian blue to the degradation process of the fibers cannot be ruled out, to the contrary, and would be interesting to investigate.…”