Conservation materials, useful life

Process material conservation is practiced by the recovery, reuse, or purification of the materials used in the processes. In the nickel deposition process the nickel solution is filtered to reduce its iron content, giving a longer life to the solution. Because the bath is dumped less often, the pollutant load is reduced. 

At the Library of Congress current estimates indicate that for materials presently identified as rare, with permanent research value, complete conservation will require about twelve thousand five hundred man years of work. Other parts of the collections are in equally serious condition (1). However, archival conservation in a library setting diminishes the role of restoration of individual artifacts in favor of carefully selected actions more immediately directed toward the greatest possible prolongation of useful life—hence our philosophy and practice of phased preservation. In practice, useful life may be projected as a thousand years or more for some items, or as little as fifty years for others. Thus, in the broadest sense, conservation comprises methods of buying time, of putting off that inevitable day when organic materials are reduced to dust. 

The last thing that many consumers likely consider when selecting a product from store shelves may be that the chemical substances in that product will ultimately enter the environment, perhaps by volatilizing to air or washing down the drain even after any solid waste is tossed in the trash for landfilling or incineration, chemicals may yet enter air, water, or soil. But matter is neither created nor destroyed. Short of nuclear reaction, fhe chemicals we use follow this principle of conservation of mass. Life cycle analyses consider the fate and transport of chemicals from the source of raw maferials through use of the product to ultimate disposal. Such assessments fundamentally begin with a mass or material balance. 

The useful life of a polymer has to be defined for conservation. Feller developed a rule of thumb for classifying materials by their photochemical stability, a useful tool that should inform aU stages in the conservation process, from planning to use (Table 2.4). In most fields, it is expected that a conservation treatment will have to be reversed in the future. For instance, picture varnishes have traditionally been replaced every 80-120 years and stained glass window installations every 2-300 years. It is likely that a material used for temporary fixing may never be entirely removed (Section 1.3). It is therefore necessary that even these have long-term stabihty. 

BLE2.4 Classification of Useful Life for Conservation Materials and ... 

A prerequisite to a corrodable material being used is that it is known to have a useful and reasonably predictable life. Planned, or unplanned downtime costs money and the intervals between planned replacements must be of reasonable duration. In practice, the replacement interval is usually conservative at first and then as experience accumulates, the intervals between planned replacements will usually extend. The main reason for choosing a planned maintenance policy is that on a discounted cash flow (DCF) calculation over the life of the plant, the cost of regular replacements including maintenance labour and downtime is less than the extra initial capital cost of a more durable material. 

NEDCC is located in Abbot Hall on the campus of Phillips Academy in Andover, Massachusetts. It is the only regional center in the country specifically oriented to conservation of library and archival materials as opposed to museum collections. Having begun life in the basement of the Merrimack Valley Textile Museum, we are pleased that we now have windows on all four sides. We have a large, spacious paper conservation laboratory, and specialized equipment such as our Israeli-made leaf caster. This is used to fill losses in book pages or documents and to reinforce crumbled edges. 

These figures are more conservative than those often quoted, and the residual values are higher. Experience indicates that used-up machinery ordinarily finds a market at second-hand prices considerably above those prevailing for junk material. Negative residual values are possible. The hfe of items like foundations is limited by that of the associated equipment. If A = amount to be realized to offset depreciation = initial cost—residual value, n = estimated life, r = rate of interest, S = annual depreciation charge, then... 

These current developments place an emphasis on the perfection of filler technology. This has resulted in the creation of many very high quality materials which are too expensive to use in most applications. There is a need to develop materials which arc substantially more cost-effective but still allow the conservation of matrix materials. This will be driven by environmental concerns. Product life cycle evaluation, an emerging development, will have a strong impact on the choice of fixture technologies and fillers associated with these technologies. REFERENCES... 

Sometimes a user pursues a more conservative course and demands a more expensive material or material processing that exceeds the minimum requirements, for example, PWHT when it is not otherwise required by the construction code and is not justified by the process. Once the user understands the reasons for the recommended material or material processing, the issue becomes a management decision. Occasionally, a user will demand the use of a material that will not meet the minimum requirements. In this simation, safety and design life requirements as well as potential consequences should be reviewed and the results documented to the user. 

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