Figure 24.—Patent model, Reinhold and Schreiber, 1880.
(NMHT 89797 [M-4327]; SI photo 73-4210.)
X-ray fluorescence analysis, response to a magnet, reaction to nitric acid, and the Vickers pyramid hardness test were among the methods of analysis used that involved no damage to the objects.
The instrument for X-ray fluorescence analysis has been modified to permit analysis of selected areas on the objects. This instrument produces, detects, and records the object’s X-ray fluorescence spectrum, which is characteristic of its composition. X-rays produced by a target in the instrument strike the object and cause it, in turn, to fluoresce, or emit, X-rays. This fluorescence is detected by a silicon crystal in the detector and dispersed into a spectrum, which is displayed on an oscilloscope screen. The entire spectrum—from 0 to 40 Ke V—can be displayed or portions of it can be expanded and displayed at an apparently higher resolution that permits differentiation between closely spaced fluorescent peaks, such as those from iron and manganese. The spectrum may be transferred from the oscilloscope to a computer for calculation of the percentage of composition and for comparison with spectra of other samples. During analysis the objects can be supported and masked by sheets of plexiglas or metal foils to limit the radiation to a certain area of the object. Masks also prevent scattering of radiation off other parts of the object and off the instrument itself, which otherwise might be detected and interpreted as less concentrated components in the object.
Brass was the most common metal used in the fabrication of eighteenth- and nineteenth-century lancets and scarificators. Upon analysis the brass was found to contain 70%-75% copper, 20%-30% zinc, and other trace elements. The blades, cocking levers, and button releases of lancets and scarificators were found to be made of ferrous metal (iron or steel). In addition to the typical brass pieces, a number of “white metal” pieces were analyzed. (The term “white metal” is used to designate any undetermined silver-colored metal alloy.) Those white metal pieces dating from the eighteenth century (a Swiss or Tyrolean fleam and an English veterinary spring lancet) were found to be composed entirely of ferrous metal. The hardness of the fleam metal indicated that it was carburized sufficiently to be made of steel. Two of the spring lancets, dating from the late nineteenth century, were found to be made of a silver-copper composition that was not rich enough in silver to be sterling silver. These lancets were probably typical of the lancets advertised as silver in the late nineteenth-century trade catalogs. About 1850 an alloy imitating silver began to be widely used in the making of surgical instruments. This was German silver or nickel-silver, an alloy containing no silver at all, but rather copper, zinc, and nickel. A patent model scarificator dating from 1851 was found to contain about 63% copper, 24% zinc, and 13% nickel. This alloy is presently called “nickel-silver 65-12” alloy. The French made scarificators out of their own version of nickel-silver that was called “maillechort.” The French circular scarificator was found to contain copper (55%-70%), nickel (10%-20%), zinc (20%-30%), and tin (less than 10%). The cases in which the lancets and scarificators were carried were covered with leather, despite the fact that several appeared to be covered with paper. X-ray analysis revealed that several cases contained tin, leading to the possibility that a tin salt was used in the dye-mordant for leather. The clasps on the cases were made of brass. One case was trimmed in gold leaf.
The most difficult item to analyze was the pen and ink drawing in black and red of a bloodletting man purported to be a fifteenth-century specimen (1480) from South Germany. The text is in German (Figure [25]).
The watermark of the paper—a horned bull (ox) with crown—is believed to have appeared in 1310 and was used widely for two hundred years. The paper was heavily sized and no feathering of the black ink or red paint appears.
The paper fluoresced only faintly under ultraviolet light and much less brightly than new paper, leading to the conclusion that the paper is not modern. Various stains on the paper fluoresce yellow, which also indicates a considerable history for the document.
The guard strip is vellum. Red stains on this strip may have been made by blood.
The inks (brown and red) may have come from different sources or been applied at different times because of their various compositions and densities. Iron and lead were found in an area of writing on the left foot. Iron is typical of an iron gall ink. Some of the lighter lines contain graphite. The red lines contain mercury and lead suggesting a mixture of vermilion and red lead.