SOME OBSERVATIONS ON THE USE OF ENZYMES IN PAPER CONSERVATION
Pia C. DeSantis
Experiments were designed to test the long term effects of a strong solution of the protease derived from A.saitoi on a degraded paper.82 Samples of newsprint83 and of a buffered Rives paper84 were aged for three days at 100°C. Five specimen groups were then devised:
It should be noted that these experiments are not meant to simulate conservation treatments but are intended to expose any adverse effects that an enzyme might have on an aged paper. To this end, the enzyme was not rinsed from group 3; and in group 4, specimens were rinsed in baths that elicit the enzyme's inactivation. In a conservation treatment, a rinse in deionized water would follow the use of Aspergillopeptidase A and would precede rinse baths such as those described in group 4.
- untreated control
- deionized water, 37°C, one hour immersion (pH 5)
- deionized water + enzyme, 0.5%, 37°C, one hour immersion (pH 6); samples not rinsed after enzyme treatment
- same as 3, but rinsed in three twenty minute baths of deionized water buffered with calcium and magnesium (pH 7.8)
- deionized water + acetic acid, 2% (pH 2.5), one hour immersion, rinsed in three twenty minute baths of deionized water buffered with calcium and magnesium (pH 7.8).
Specimen group 2 serves as a wash control, since these specimens received a one hour soak in pure deionized water from the same column as that used to make up the solutions in groups 3, 4, and 5.85 Moreover, the bath water temperature was maintained at 37°C so that this bath would be comparable to the enzyme baths. The rinse baths used for specimen groups 3, 4, and 5 came from the same column,86 and the acetic acid bath was kept covered so that it would not decrease in strength. Acetic acid and enzyme treated specimens are compared in this study because some conservators still prefer to use acetic acid rather than enzymes for the removal of old glue accretions.
The temperture optimum of 37°C was maintained during the experiments by the use of hot water and metal containers. Hot tapwater was run into the lab's stainless steel sink, a smaller stainless steel container was placed within it, and this smaller container was filled with boiling water. The heated solutions were poured into enamel trays that had been placed in the smaller container and equipped with thermometers and plate glass covers. The temperature of the heated solutions was checked and the samples were agitated periodically. Additional boiling water was added to the smaller stainless steel container as necessary to maintain the temperature of the heated solutions at 37°C.
Samples were kept in blocks during treatment to facilitate handling, and cut to TAPPI specifications just prior to being placed in the enviornmental chamber.
Each specimen group comprised twenty specimens. After treatment, ten specimens were oven aged to provide post-aged data. Post-aged specimens of Rives were aged for three days at 100°C; newsprint was aged separately for four days at 100°C. (A dry oven was used since a humid aging oven was not available.) Specimens treated with acetic acid were also separated from the other four specimen groups during aging.
Brightness tests were run at 457 nanometers on the Photovolt model 670 Reflection Meter at the Preservation Office of the Library of Congress.
Fold endurance testing followed the specifications for conditioning and the procedures that are presented in TAPPI methods T402 os-70 and T511 su-69. The testing was performed in the controlled environment chamber at the National Gallery of Art on their MIT foldendurance tester model #1, set at 500 grams and sixty double folds per minute. Measurements of pH followed TAPPI method T509 os77 for cold extraction.87