Historic artifacts

The third category of metallic artifacts includes collections of a most different provenance—such as scientific instruments, fine arts, historic pieces, ethnographic specimens, etc., which are usually kept in museums. Contrary to the belief that an object is safe once it enters a museum, certain storage or display conditions may lead to corrosive reactions that are different from those found in the natural environment [264, 265]. Some of these dangers come from off-gassing from materials used to build display cases and rooms, as well as air pollution introduced by visitors. 

The most common gaseous pollutants released by construction materials, are NOx, SO2, H2S, O3, HCOOH, CH3COOH and HCHO, which potentially interact with metal alloys, either directly or as catalytic reagents [266]. The presence of 

Silver and silver-copper alloys are often even more sensitive to sulfur compounds—the effect is catalyzed in the presence of oxidizing species and high relative humidity [268]. The resulting surface layer—dark, thin and adherent when developed on a polished surface—usually acts as a good physical barrier that slows down the tarnishing reactions. However, since silver objects are expected to be shiny. 

The few reported cases concerning other metals, like zinc, aluminum, and magnesium, attest their susceptibility to corrosion due to volatile compounds in the museum environment [271]. Iron is naturally vulnerable to atmospheric corrosion whatever the pollutants, and the conservation of ferrous artifacts implicates a precise control of relative humidity, often requiring a surface protection like varnish, wax, or oil [272]. 

For all the above reasons, the concern about environment characterization and monitoring is expanding and a new discipline— preventive conservation has emerged. Its goal is to adapt the environment to materials constituting artefacts, thus minimizing further deterioration. 

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The titles we use, such as microwave or X-ray are just historical artifacts, and merely describe the way scientists first encountered them. 

Synthetic polymers, often possessing uniquely desirable working proper- ties and physical appearance, are finding ever wider use by artists and conservators. For example, poly (vinyl acetate) emulsions have been used for collages (4,5), the production and conservation of books (6,7), and the conservation of textiles and paintings (8,9). It has become essential to study the behavior of new materials and to evaluate their long-term behavior as individual materials and as components in the complex systems which make up artistic and historic artifacts. Our experience with a wide range of natural and synthetic polymers—e.g.,... 

Those who document historic artifacts to establish provenance and date or who examine components to assess condition use investigation methods that are as nearly nondestructive as possible. Nondestructive... 

More than a century later, the auto industry is at a similar crossroads, with competing technologies. Just as in 1900, there will be turns in the road, technical breakthroughs and factors that no one has thought of. New propulsion systems will emerge and the internal-combustion engine may become a historical artifact, after what may turn out to be, in history s long sweep, a relatively brief hundred year run. 

Radiocarbon dating was used in the authentication study of the Shroud of Turin. It is an essentially nondestructive technique and is valuable in estimating the age of historical artifacts. 

It is not obvious why (13.1.31) is called an electrocapillary equation. The name is a historic artifact derived from the early application of this equation to the interpretation of measurements of surface tension at mercury-electrolyte interfaces (1-4, 6-8). The earliest measurements of this sort were carried out by Lippmann, who invented a device called a capillary electrometer for the purpose (9). Its principle involves null balance. The downward pressure created by a mercury column is controlled so that the mercury-solution interface, which is confined to a capillary, does not move. In this balanced condition, the upward force exerted by the surface tension exactly equals the downward mechanical force. Because the method relies on null detection, it is capable of great precision. Elaborated approaches are still used. These instruments yield electrocapillary curves, which are simply plots of surface tension versus potential. 

Ethics of Consolidation. An ethical dilemma is inherent to the process of consolidation. Extrinsic material (consolidant) becomes bound to the original material and, for practical purposes, becomes inextricable from that fabric. Any extrinsic substance incorporated into a historic artifact adulterates the original fabric. Factual interpretation becomes more diflScult as the fabric is obscured or altered. 

Museum and archive specimens demand and warrant a level of protection from pests (primarily Insects, occasionally fungi) that approaches absolute. Historical artifacts and preserved members of extinct species are not, unlike commercial products, renewable commodities. Consequently, a damage threshold or allowable loss level Is not possible If valuable collections are to be maintained. Most collections are, however, dynamic, with the addition of new Itons, and the removal of others for loan or study, constantly taking place. Both the storage and the flux of a viable collection have the potential for Infestation and Irreparable damage. Therefore, pest protection Is an Important and constant responsibility of a museum s staff. 

Along the same lines, try to anticipate words that your audience may be unfamiliar with, whether they re spoken by the narrator (and a more familiar word can t be substituted) or spoken by an interviewee or someone on camera. If the word s meaning is not clear in the context, you may need to set it up. For example, suppose the historic artifacts you re presenting on screen include a bill of sale for a frigate. You might set it up as, That day, the general placed an order for a new sailing ship, one outfitted for war. 

Note The sign convention used for EA is in contradiction to that usually found in thermodynamics, an unfortunate historical artifact. 

There are increasing applications for Raman spectroscopy. One application is its use in the identification of different pigments in the characterization of historical artifacts. Table 10.5 lists blue pigments used on or before about 1850 that have been identified by Raman spectroscopy. 

Radioactivity is also used to help determine the mechanisms of chemical reactions, to trace the movement of atoms in biological systems and the environment, and to date historical artifacts. 

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