6. Discussion of Results
The amount of DEAE per unit area of surface of the acrylic glazing on “Salon Rose Roix” was determined to be 1.7 ng per square meter. Fannick, et al (1983) reported that they found 30 mg of DEAE per square meter of exposed surface from their analysis of “bulk samples” of plastic film that had been exposed to the atmosphere of the Johnson Museum, Cornell University “for years”. 30 mg of DEAE per square meter is 30 mg/rn2 x 106 ng/mg 10-6 m2/mm2 = 30 ng(deae)/mm2 or an amount roughly 18 times greater than that observed on the glazing of “Salon Rose Roix”.
Very little free, unreacted DEAE was found on any surface. This is not surprising. DEAE is a volatile liquid. A drop on a microscope slide evaporates to dryness in about 1 minute. Only if it reacts with compounds in the painting will it be present, and then, only as a “fixed”, involatile reaction product.
There does appear to have been some reaction of DEAE with varnish and paint media.
There appear to be two mechanisms operating. In one, the alcohol group of the DEAE reacts with acid groups in the media to produce esters (DEAE esters). In the other, the nitrogen of the amine group in DEAE reacts with the acid groups in the media to produce substituted ammonium carboxylate salts (DEAE carboxylates).
There is a complex interaction between DEAE, acids, esters, and carboxylate salts in the medium, and acidic or basic reagents added to the medium during trealment. This interaction is not yet clear, but the following is probably true. The DEAE esters are not likely to be water soluble, whereas the DEAE carboxylate salts probably are. Any medium that has a significant concentration of DEAE carboxylate salt may be affected abnormally by water.
Although the small amounts of DEAE reaction products detected may be responsible for some of the subtle effects attributed to DEAE contamination, no sample analyzed has chemically reacted very much with DEAE, and in those samples where DEAE reaction products were found, only relatively small amounts of these were present.
Samples from some paintings contain water soluble or water sensitive components such as carbohydrates and proteins, which are unrelated to DEAE contamination. In these paintings, the effects attributed to DEAE contamination might be due to the presence of the water sensitive components.
No SEM examination was carried out during this work. Upon reflection, SEM examination did not seem to be an appropriate technique to determine damage caused by DEAE contamination. While it may be possible to characterize the current structure of surfaces or cross-sections of paintings, this will only give a snap-shot of the current state of the paintings. This will not permit any assessment of changes caused by exposure to DEAE because we have no data on the structure of the paintings before DEAE exposure for comparison. SEM or other microscopical analysis may be of some use in determining how treatments change the structure, but in the absence of data on how the painting would respond if it had not been exposed to DEAE, changes observed cannot be directly related to the effects of DEAE.