EMBEDDING PAINT CROSS-SECTION SAMPLES IN POLYESTER RESINS: PROBLEMS AND SOLUTIONS
MICHELE DERRICK, LUIZ SOUZA, TANYA KIESLICH, HENRY FLORSHEIM, & DUSAN STULIK
Preventing infiltration of the embedding resin into a sample will allow it to maintain its original physical and optical characteristics. This may or may not be desirable depending on the type of sample and the type of analyses to be done.
In the case of a porous, powdery sample the advantages of resin impregnation during embedding are that it will produce a solid, consolidated sample that may be highly polished to a flat, smooth surface. These qualities are useful for photomicrography, pigment identification, and SEM/EDS analysis. If needed, the sample should microtome well into intact thin sections. However, interpretation of any staining or infrared analysis would be difficult due to the presence of the resin within the sample. One viable option would be to perform infrared analysis on particles from a corresponding nonembedded portion of the sample.
Conversely, if this sample were not infiltrated with resin, the resultant embedment would contain a fragile and poorly cohesive sample. Some particles may fall out of the sample during polishing, and microtoming the sample will be difficult and time consuming. The advantage of an unadulterated sample is that any analysis method used for examining the sample is doing just that, examining the sample and not any added component. Resin infiltration may particularly affect the results of photomicrography, fluorescence, staining, colorimetry, or infrared microspectroscopy. The examination and detection of glazes and other thin, organic layers may be very susceptible to resin infiltration.
In our experience, the porous, crumbling sample is a rare, worst-case situation. Many cohesive samples that were not expected to be infiltrated were found to contain polyester resin after embedding. Thus, it is important to recognize that infiltration can occur and make a determination whether it is necessary to prevent the infiltration.