Conservation of Instruments - Part 3

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  Article taken from "Backsights" Magazine published by Surveyors Historical Society


by David St. John




Generally speaking, contaminants can be regarded as any material or energy that affects the function of an artifact or the anticipated results of a restoration process.

When thinking about long term preservation of an artifact, contamination in the form of particulates, chemicals, biological matter and electrostatic charges can have a significant affect on the anticipated results of a restoration project.  Regardless of the type of contamination, the environment and the handling present many opportunities for unwanted materials to enter the conservation process.  At first one might consider gross contamination like oil, grease, dirt and fingerprints, etc.; contamination is much more subtle!  Thought has to impact simple condensation from hands covered with "white gloves", a cough, a sneeze, dandruff, atmospheric contamination from city pollutants or sodium nuclei near to an ocean.  These contaminants, their source and control should be considered an important element of a restoration task.

Fortunately, much of the technique for the identification and control of contamination exists in science and industry, especially in the field of photolithography related to micro-circuits and fine line engraving.  A conservator must gain practical knowledge about the effects of contamination, identification of the sources and necessary controls which would be of advantage to the conservation facility or museum.


Equally important as the control of contamination is the removal of unwanted materials through advanced cleaning techniques.  This can be a complex subject and knowledge is necessary about the characteristics of contamination, mechanisms of retention, substrates and techniques of removal.  This will provide a significant inventory of effective tools to the conservator and enhance the objective of long term preservation.  Modern technology has provided an insight to the nature of contamination and industry has responded with an assortment of powerful cleaning agents.  These surface active agents must be carefully selected and used with appropriate procedure.  Many agents will not only clean substrates but assist in the removal of corrosion products and prepare surfaces for subsequent operations.

Selection of cleaning materials and methods relate to the identification of the contaminant and the compatibility of the substrate.  The object of this study is related to contamination and its control.  There is the added difficulty of determining substrate compatibility and possible effects on subsequent operations.  The subject of cleaning is further complicated with proprietary information held by manufacturers of cleaning materials.  One must know what he is working with in order to provide appropriate controls.  Many cleaning substances are toxic or at the least, harmful to the practitioner as well as the artifact.  There is also the subject of waste disposal according to State and Federal regulations for a small generator.

Such considerations make the selection of an effective cleaning procedure more complex.  The methods in use by industry have been successful and several have been applied to the restoration process.  Still, cleaning and contamination are subjects to be carefully studied.


The destructive attack on a metal by chemical or electrochemical reaction with the environment is a problem that a conservator may deal with on a regular basis.  More often than not, the conservator has little knowledge of the history of use or storage of an artifact.  Whatever the form of corrosion, the conservator must neutralize the reaction, remove the corrosion products and take measures to seal off the surface from the environment to maintain the artifact in a stabilized state.

The type and rate of corrosion are affected by many factors which relate to the history of use and storage.  The metal properties and impurities must also be considered.  The subject of corrosion is complex.  Fortunately there exists active research in this area and extensive literature is available to guide the researcher and conservator.

There are several forms of corrosion but the main interest at this time is related to intergranular, galvanic and stress corrosion.  There are many contributors to corrosion:  substrate porosity, surface finish, fungi, bacteria, moisture, galvanic couple, atmospheric pollutants, and even a process designed to stabilize one form of corrosion may cause another.

The restorer must gain an understanding of the forms of corrosion, develop appropriate examination procedures and treatments if they do not already exist, keeping long term conservation in mind.  Such an open ended study is fascinating.  Collecting data which is specifically related to problems associated with early surveying instruments is only one aspect of the task.  Any definitive procedure must be verified against time.  Short term accelerated testing does not supply absolute information to predict the effectiveness of a method.  Such data may support probable success but intrusive testing will be required for many years to substantiate the validity of a method.


One would not commonly associate electrostatic charges with the conservation of utilitarian artifacts such as surveying instruments, octants or sextants.  There are several elements to a restoration process which would not seem to be affected by short term environmental conditions.  When long term preservation is the goal, certain areas of practice deserve review.  In fact the whole process of conservation is under review as what was the paradigm of technique even ten years ago has changed with the influx of new materials and scientific equipment in this present age.  Surely things will continue to change in the coming years.  This is why the "Principle of Reversibility" exists within the conservation community.  What was done several years ago may well be reversed and done again with newer materials and methods in order to better preserve a valuable artifact.

The typical conservation facility is something less than a laboratory.  The work areas are reasonably well ordered with the use of good equipment and modern, if not advanced materials being commonly applied during treatments.  Many of these materials and substrates being treated can carry an electron charge.   Without attention to the performance of work, static charges can easily exceed 10,000 volts.  This can be demonstrated simply by moving from one place to another.  The situation is aggravated with the reduction of humidity.  The author has concern for the reliability of long term conservation technique.  The generation of excess electron charges is seen as an immediate deterrent to the success of an otherwise sound technique.

The initial concern relates to contamination free surfaces, appropriate cleaning technique, surface preparation and hand lacquering operations.  Electrostatic discharge may frequently be at a level below the threshold of feeling, yet cause serious difficulty.  Highly charged surfaces and lacquers attract airborne particulates which become entrapped.  These particulates disrupt the permeability of coatings.  Much of this contamination is hygroscopic and in combination with the environment and humidity can cause corrosion within a short period of time.

Conservators should review existing practice and gain an understanding of basic methods to control static electricity during the performance of work.  The achievement of uniform contamination free coating is very important to long term conservation.  There is reason to suspect that static electricity has an impact on surfaces of artifacts during display and storage.  This is a subject for future study.


One of the objectives of establishing a Standard of Practice is to secure detailed technical and physical information from each artifact for future reference.  Aside from routine written and photographic documentation, detailed drawings are made of components and assemblies of each instrument.  This fund of knowledge provides for component replacement as a service to institutions and collectors.

In this case, the term "Replication" is specifically used to differentiate from the common term "fabricate".  It takes a little effort for good mechanic to machine a component to a drawing.  In terms of replication, attention to additional detail is required.

Given appropriate material, the first consideration is to fabricate the component with the intrinsic errors and features imparted by the original maker, time and wear from field use and damage common to the part are important.  There are also the natural effects of the environment, corrosion and patina.  Colors of metals and original protective finishes must also be considered as a separate problem.  In the final analysis, the new component is a faithful reproduction of the original.

The second consideration is the inclusion of this type of effort in the documentation report in detail so that provenance not be confused.  Enough puzzles already exist!  Full disclosure of replication is mandated by the Standard of Practice.  The restorer's mark should be placed in an inconspicuous manner on each component replicated.

The practice of replication by any party should perhaps be published within the conservation community to the end that ethical constraints are enforced at the highest level.

In principle, a dedicated conservator can supply important services to collectors, institutions and the conservation community at large through legitimate replication.  This service should be done openly to assure confidence within the profession and become thoroughly documented within the reports that accompany the artifact.




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