In the 1990s there was a pioneering study on the use of parylene to strengthen brittle book paper performed by Don Etherington, David Grattan, and Bruce Humphrey. Ultimately their research did demonstrate that parylene strengthened weak, brittle paper, but several concerns regarding the material’s long term effects were raised; such as reversibility and the uncertainty of its aging properties. John Baty and his colleagues at the Heritage Science for Conservation Research Center at Johns Hopkins University, sought to reexamine the potential for using parylene to strengthen brittle paper, given the improved scientific instruments and analysis methods available today. Their research sought to answer five primary research questions: does parylene strengthen paper, what is the permanence of its effect, what are the side effects, how can parylene treatment be scaled up, and how can it be reversed. Currently they have answered the first two and are conducting ongoing research.
Parylene is applied to brittle books by using a chamber that draws a vacuum and essentially pulls sublimated parylene through the system. The amount of parylene dimer that is added to the chamber directly correlates to the thickness of the deposited film. Previous research had not optimized the amount of parylene needed to achieve a desirable film layer, so this was a primary goal for Baty and his colleagues. The success of the treatment was evaluated using three mechanical paper strength tests: tensile testing, the MIT fold endurance test, and the Elmendorf tear test.
Baty and his team found that using 3 grams of parylene was sufficient to strengthen brittle paper to the point that it behaved similarly to modern wood pulp paper and only imparted a smoother appearance to its surface. 5 grams of the dimer was too much and conservators inspecting the pages concluded that the paper had a more “plasticky” and stiff feel to it. The three mechanical tests did indicate that the brittle paper samples were strengthened with the addition of a parylene coating, but there are still questions regarding this treatment’s reversibility and side effects that remain to be answered by Baty and his team in subsequent research.
Author: Kathy Lechuga
43rd Annual Meeting – Research and Technical Studies, May 15, “The Deacidification of Contemporary Drawings: A Safe Method Based on Nanotechnology” by Giovanna Poggi
The degradation of cellulose-based materials, such as paper and canvas, is exacerbated by the presence of acidity caused by the natural aging process, various sizings, surface coatings, inks, or other papermaking products. Conservators attempt to mitigate this problem by the use of alkaline compounds to deacidify the substrate and impart an alkaline reserve within the fibers to counteract future acidity. In the case of paper-based objects, deacidification is most commonly accomplished by either washing in an alkaline bath or spraying on a solvent-based dispersion solution of micro-particles of magnesium or calcium.
Dr. Poggi’s talk presented research into a new method that can be used to deacidify paper-based objects using an apolar solvent dispersion of alkaline nanoparticles applied topically (an airbrush was used in these experiments), without the need for full immersion. The benefit of using nanoparticles for deacidification is that these particles have a higher surface area which react more readily with acidic compounds, creating a faster neutralization reaction; they are more homogenous in structure; and nanoparticles are able to penetrate further through the paper fibers, surface coatings, and sizing than micron sized particles. This research was conducted as part of the broader Nano for Art project, which seeks to devise new methods for the conservation and preservation of art using nanotechnology. More information can be found at their website: http://www.nanoforart.eu/.
Through the use of solvothermal reactions, Dr. Poggi and her colleagues were able to procure nano-sized particles of a crystallized form of CaOH in ethanol. They discovered that an alcohol based system created a stable, highly concentrated dispersion without the need for further purification and was very effective at deacidification. However, this solution could not be applied to more modern papers containing inks which were sensitive to alcohol. Apolar solvents were explored due to the fact that they would not adversely impact the topography of cellulose substrates. A variety of problematic inks were tested, such as ballpoint pen and felt tip marker, until it was determined that cyclohexane was the most appropriate solvent to use. During experimentation on both mockups and actual works of art, it was found that the cyclohexane dispersion did not adversely affect modern inks nor the topography of the paper substrates. Aging tests were performed on samples and indicated that papers treated with the nanoparticle dispersion discolored less and had an improved degree of polymerization when compared to aged, untreated samples.
Dr. Poggi’s presentation was very interesting and I’m looking forward to learning more about the use of these nanoparticle solutions to achieve a more effective and hopefully long lasting form of deacidification.