The technique of painted enamels is described in great detail, based on observation under the microscope of the complex layers of translucent colors and on examination of cross-sections of samples in areas of loss. Semi-quantitative spectrographic analysis of minute samples of enamel indicated the metallic oxides or carbonates used to produce certain colors, while a nondestructive test of a blue enamel area by X-ray fluorescence provided further information about the colorant components of the material. Characteristic techniques include: delineation of facial features and other details by scraping away a line through the enamel before firing; application of decorative elements such as flowers and jewels with a tiny piece of silver foil underneath, and the use of thin washes on flesh tones as a final step. Technical distinctions in the methods of different enamellers of the period are pointed out. In the period 1470-1530 the transparent flux was either a soft lead glass or a softer leadless-alkaline glass, with a melting point of around 1300°F. Excessive amounts of soda ash (Na₂ CO₃) were necessary to produce this low melting point. During subsequent centuries the sodium tended to be dissolved out of the glass by exposure to moisture. Alkaline solutions would then accumulate on the surface and penetrate through minute cracks, leaving crystalline deposits which occupied more space than the liquids, eventually exerting sufficient force to dislodge flakes of enamel. Analysis of samples of this white crystalline efflorescence by emission spectrography and X-ray diffraction confirmed the presence of large percentages of sodium and calcium. Treatment involved removal of the soluble alkaline efflorescence by repeated washing in water, concluding with baths in ethyl alcohol and finally in acetone. Coating the surface with a clear synthetic resin, displaying or storing the enamel plaques in an upright position, and maintaining a humidity range between 50% and 60% R. H. are vital factors in preventing a recurrence of deterioration. -- AATA