Analysis of Agarose, Carbopol, and Laponite Gel Poultices in Paper Conservation

Abstract

Agarose, Carbopol, and Laponite gels were evaluated as alternatives to cellulose ether poultices for the local removal of moisture-sensitive adhesives on paper artifacts. These gels have noticeably different working properties than cellulose ethers, and are useful in a variety of paper conservation applications. The color stability of these materials was analyzed in dry powder form and as gel residues on paper. Analysis was performed by UV-visible spectroscopy, combined with visual examination under normal illumination and long-wave ultraviolet irradiation. Since earlier studies demonstrated that both Carbopol and Laponite contribute to the discoloration of paper after artificial aging, this study tested the effectiveness of a barrier tissue to block the deposition of residues on paper. Paper samples treated with Laponite were analyzed with a scanning electron microscope coupled with energy dispersive x-ray fluorescence spectroscopy to identify residues. Visual and ultraviolet examination techniques demonstrated that Carbopol (pH adjusted with sodium hydroxide) and Laponite caused discoloration on paper when applied directly, and that a barrier tissue was effective at blocking the deposition of residues. Agarose did not show adverse effects.