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CONSERVATION OF INSTRUMENTS PART 2 by David St. John The author came to the field of conservation by coincidence. As a designer of optical instruments, standards became a lifeline to the success of any technical assignment. With regard to the conservation of scientific instruments, the lack of a standard of practice was quickly recognized. Research of related standards within the industry helped from guidelines for preserving instruments of our surveying history. The details of a practical standard began to accumulate over a period of years. As interest in surveying history continues to grow, so will the need for appropriate conservation. There is an awareness that any standard must be an enabling tool for a conservator to implement methods in an easily understood, economical and convenient manner. Any standard should relate to a number of professionals within the conservation field. The document must facilitate communication. The initial thought was to develop a document specifically for the restorer, to be prescriptive and satisfy the technical aspects of conservation at a practical level. With time, a concern developed about individuals who might have important requirements other than the restorer and there would be difficulties relating to an isolated standard. THE INSTRUMENTS The document is presently related to experience with limited types of instruments used in the surveying profession. While other types have been accepted for restoration, the standard is centered on the following: Surveyor's Compass Octants Microscopes Spirit Levels Plane Table Alidades Refracting Telescopes Transits Goniometers Planimeters Theodolites Tilting Levels Sextants Dumpy Levels Inclinometers Wye Levels THE MATERIALS Consider the following list of materials found in a limited group of instruments from a single profession. Add the hundreds of instruments from all scientific endeavors and the list becomes extensive. Preservation is a long term concept. Conservators tend to specialize in a narrow field but gain intimate knowledge about materials and treatments. A standard of practice could be a focal point for dissemination of important information on conservation techniques and current practice. Bell Metals Cloth Brass Paper Bronze Spider Web Copper Leather Pewter Varnish Lead Optical Cements Zinc Lacquer Gold Animal Glue Silver Lubricants Nickel Silver Ash Aluminum Lignum vitae Invar Maple Iron Oak Solder Ebony Tool Steel Mahogany Optical Glass Ivory Float Glass Cherry Diamond DATA COLLECTION Characteristics that differentiate one make from another are important from an historical perspective. For the most part these details are easily captured for reference. The collection of more intimate detail provides historical advantage and a sensitive exposure to the work of the maker throughout his life. Studies which provide historical advantage essentially are never complete. The details take years to accumulate but eventually a substantial fund of knowledge will exist for others to study. The present characteristics being collected are: Spindle tapers used between 1800 and 1900 Thread classification of different makers Spirit Vial configurations, glass type and condition Materials and alloys used Construction techniques of the various makers Lacquers and colors, condition and physical parameters Lubricants and related galvanic couple Knurls and chamfers related to each maker Compass needle configurations Optical properties of systems and elements Casting quality and designs of each maker Machined surfaces, finish, tool marks, feedlines, tell-tales Divided circle characteristics and distribution of errors Hand engravings and embellishments Innovative features for the period SPECIFIC STUDIES Permeability of brushed lacquers Surface preparation and adhesion of lacquers Color reproduction and bleaching effects of solar radiation Color fastness with the chemical bleaching in micro-climates of display cases Fungus treatments on early glasses Sterilization techniques and substrate compatibility Artificial aging of new lacquers Corrosion treatments and vacuum impregnation of dielectric materials Lubricants for use in long term preservation Atmospheric pollution effects on artifacts Microbiological contribution to corrosion Resolving questions related to the principle of reversibility PHOTOGRAPHIC DOCUMENTATION The use of appropriate camera equipment and lighting provides an important record of the artifact, its details and condition before, during and after treatment. The use of color and orthochromatic film captures intimate characteristics which define, in part, the intentions of the maker and his execution of thought. Such information provides sensitive historical advantage. Photography also serves the needs of training other conservators and provides for presentations both general and professional. There is a story to tell about instrument conservation, its problems and solutions. Photographic records have other benefits. Aside from being part of a documentation report of an assignment, photographs provide a means for communicating to a broader audience through articles and technical papers for the general public and within the profession. WRITTEN DOCUMENTATION The author, having been trained as an instrument maker, has personal insight into the type of details which should be collected to fully characterize an instrument and provide data to gain understanding of the thoughts and abilities of the maker. A systematic approach enables the conservator to retrieve sensitive information which often proves valuable in the determination of provenance. Selected features help greatly to identify a maker and the period in which the instrument was fabricated. In addition to securing information of historical advantage, an appropriate examination provides the necessary information on the stage of condition of the artifact. Each restoration is in a sense a design task in reverse. The author is interested in "functional restoration". It is necessary to gather a significant fund of knowledge from a an artifact in order to plan an approach for bringing back an instrument to its original function and appearance without an improvement on the work of the maker. The examination report provides a tool for communication with other professionals and enables the task of restoration to be defined in terms of difficulty and cost. This helps in third party evaluations and estimates based on the contents of the report. Once it is agreed to proceed, further documentation is required to explain the materials and methods used. The end result is a document that provides explicit information about the instrument, its maker, and the actual restoration. This fund of knowledge is then available for use by other interested parties in future generations. Ultimately such information can be supplied through a networking system within the conservation community, with convenient access by everyone. COPYRIGHTED, ALL RIGHTS RESERVED, BENCHMARK INSTRUMENTS
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Article taken from "Backsights"
Magazine published by Surveyors Historical Society