Characterization of the Aniline Dyes in the Colored Papers of Jose Posada’s Prints Using Time of Flight-Secondary Ion Mass Spectroscopy (ToF-SIMS) to Aid in Developing a Treatment Protocol for the Removal of Pressure-Sensitive Tapes

Jose Guadalupe Posada (1852-1913) was a prolific and influential Mexican printmaker; he produced thousands of images printed on a variety of poor-quality papers, often colored with vibrant but fugitive aniline dyes. The Amon Carter Museum of American Art has a large collection of approximately 400 prints attributed to Posada, many of which retain their bright color. A number of these are unstable due to oxidized pressure-sensitive tape residue, penetrating and weakening the short-fibered paper. In addition, aniline dyes are sensitive to solvents, complicating treatment.

Because aniline dyes have varying sensitives to different solvents it is necessary to characterize them before an appropriate treatment protocol can be developed. A previous study of Posada’s prints identified several aniline dyes using Fourier Transform (FT)-Raman spectroscopy. Of these, the yellow dyes could not be fully characterized. In this study, ToF-SIMS was used to discern the dyes present in the colored papers with particular focus on the yellow dyes.

ToF-SIMS is emerging as a valuable analytical technique for the identification of organic and inorganic components. Its high sensitivity and small sample size requirements make it potentially useful for the analysis of dyes and works on paper. For this study a selection of Posada’s prints in various colors from the Amon Carter’s collection were examined using ToF-SIMS. In addition, two paper pulp dye manuals containing naturally aged, dyed-paper samples contemporary to the Posada prints were also analyzed as known references. Preliminary analysis has produced significant data for all the dyes analyzed.

As part of developing a treatment protocol for the Posada prints, an experiment was set up using artificially aged paper and tapes to simulate the removal of oxidized tape from fragile dyed papers. A variety of methods were employed. Samples were created by applying Scotch MagicTM tape (acetate backing; acrylic adhesive), 3M 2214 paper tape (crepe paper backing; rubber adhesive), gummed brown paper tape (kraft paper backing; starch adhesive), and Slime rubber cement to several c.1900s dyed and undyed broadsides, mimicking the Posada prints. The samples were then ‘treated’ with solvent and suction, solvent vapor via plasma, and rigid Gellan gum impregnated with solvent. The samples were imaged using visible light and Ultra-Violet (UV) before and after treatment, along with spectrophotometer readings to monitor and record any changes in the samples.

Because aniline dyes are prevalent in many turn of the century objects, as are oxidized tapes, developing an effective treatment protocol has tremendous potential benefit.

Stacey Kelly, Paper Conservation Fellow
Amon Carter Museum of American Art


Tape samples on various dyed and undyed papers before artificial aging