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Thursday, May 16 • 2:00pm - 2:30pm
(New Tools and Techniques: Let’s Talk about Gels!) High Acyl Gellan Gum in Parchment Conservation

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The novel application of high acyl gellan gum to parchment for the water-based reduction of aged adhesive is described. Parchment is extremely sensitive to moisture, and water-based treatment strategies can cause planar deformation, transparency, or brittleness, usually only dry treatment options are attempted. Since gels provide the conservator with controllable water delivery, the application of gels to parchment conservation is especially appealing in instances such as removing adhesive residues, local humidification and flattening, and removing surface grime. The high acyl gellan gum (HAGG) gels described below were developed in the context of the full treatment of a 12th-century Italian illuminated manuscript. The HAGG gels were successfully applied during two instances: the humidification and lifting of a parchment manuscript waste pastedown adhered to wood and the softening of adhesive residues for mechanical reduction.

Gels commonly used in paper conservation, such as agarose and low acyl gellan gum, have the disadvantage of being too wet and/or too rigid to use on the moisture-sensitive and often distorted surface of parchment. HAGG is a water-soluble polysaccharide similar to low acyl gellan gum, but HAGG is much more flexible than the low acyl variety. Therefore, HAGG can easily conform to and make contact with the uneven topography of cockled parchment or spine folds. Also, HAGG gels can achieve gelation after the addition of ethanol during cooking, unlike low-acyl gellan gum which must be soaked in solvent after gelation. Soaking a gel in solvent increases the rigidity of the gel. Adding the solvent before gelation has the added advantage of more control over the amount of solvent incorporated into the gel. Finally, HAGG can also be made with a buffered solution to accommodate enzymes and chelators.

The two most successful HAGG gel recipes were 1) .5 g HAGG and 50 mL deionized water with magnesium hydroxide added to elevate the pH and 2) 25 mL water, 25 mL ethanol, and .5 g HAGG. Initial tests of the incorporation of ⍺-amylase to 1% HAGG made with a buffer of sodium citrate indicate that the gel can be a successful vehicle for the delivery of enzymes to break down starch components in adhesives. In addition to practical applications in treatment, the efficacy of HAGG in the reduction of surface grime and surface coatings will be further tested on antique parchment samples. Long-term effects of introducing ethanol and elevated pH levels to antique parchment will be explored with artificial ageing tests on sacrificial antique parchment.

Thursday May 16, 2019 2:00pm - 2:30pm EDT
Nehantic/Pequot/Paugussett Rooms Sky Convention Center, Mohegan Sun
  General Session, New Tools and Techniques: Let’s Talk about Gels!