The conservation of complex machinery, clocks and technical or scientific equipment requires specialist knowledge in the history and usage of such objects. Owners or custodians of these objects must find a balance between demonstrating how these objects were originally used (for example, by replacing their worn parts with replicas) or keeping them as display objects only.
Video: The Gilt-Brass and Silver Table Clock with Astronomical and Calendrical Dials by David Weber (1623/24−1704) was featured in an exhibition Precision and Splendor: Clocks and Watches at The Frick Collection 2014.
Caring for historic farm machinery is a requirement for museums and historical societies with farm collections, museum advisors and private collectors. The conservation of clocks and watches (horological conservation) is a specialisation that combines science, art, history and preservation. Preservation of these objects is important so significant historical value and knowledge can be retained.
Types of deterioration
Usually, deterioration in equipment that is functional is a product of wear through usage. Particularly, wear of the bearings, pivots, components that rotate or slide, on surfaces of gear teeth that are in contact with one another, and more generally, when any surface is in contact with another surface, whether it be sliding or rotating.
Dust, dirt and other airborne abrasives cause problems when particles interfere with the machinery components, such as between a pivot and a bearing. Slow abrasion of a surface over time can cause deterioration and while lubrication is a common treatment for machinery and clocks, without the pivots being polished or replaced, deterioration will only continue to occur.
The combination of cleaning agents and lubricants used over time also present problems as without properly removing one lubricant from the surface of an object or its components, a chemical reaction may occur between the two products and increase degradation. Furthermore, many older lubricants were made from organic sources such as sperm whales or porpoises and contain various acids. Such lubricants accelerate corrosion in metals.
Some scientific equipment and machinery may be composed of composite materials including painted surfaces, metals, leather, felt, wood and paper. Combinations of materials can increase the risk of deterioration, for instance, when a corroding metal buckle is in contact with leather.
As with many objects made from a combination of metals and other materials, corrosion is a common problem. Machinery in particular is often exposed to the elements, with water, salt and fluctuations in temperature and relative humidity accelerating the chemical process of corrosion.
Lubrication of clocks and other machinery is a key component of conservation and preservation. However, the sliding surfaces within clocks and other technical equipment are impossible to separate at the atomic or crystalline level. Therefore, wear can be reduced, but not completely halted, by using appropriately chosen lubricants with long polar chains.
Cleaning of a clock or other complex technical equipment requires specialist knowledge. Correct servicing, examination and re-lubrication by dismantling each component and then re-assembling of an object is important. Clocks can consist of up to five hundred individual components!
Cleaning using ammonia-based solutions is not recommended, and instead alcohols or hydrocarbons in combination with manual labour using fine brass and steel brushes, as well as non-metallic brushes is required.
Corrosion can be reduced in the mechanisms of machinery that have both brass and steel components by reserving brushes for each material. Cleaning with metallic brushes should be kept to a minimum in order to reduce damage to oxide layers.
Storing machinery and farm equipment away in stable environments away from moisture can reduce deterioration through preventive conservation measures. In historic farm equipment, remnants of grains and vegetable matter might attract pests and can be removed and stored separately for documentation purposes.
Engines and mechanical internals of farm equipment should be checked for remaining substances such as water, oils and fuels. Historic scientific and other technical equipment may contain hazardous materials – chemical or biochemical – and should be handled with caution.
AICCM has a Special Interest Group for those interested in the conservation of objects, which includes machinery, clocks and scientific equipment. Join this group, contribute to its activities, or speak to a specialist conservator.