Conservation and restoration of silver objects

Last updated
A 1919 painting by Fritz Stotz depicting women polishing and cleaning household silver Fritz Stotz Madchen beim Silberputzen 1919.jpg
A 1919 painting by Fritz Stotz depicting women polishing and cleaning household silver

The conservation and restoration of silver objects is an activity dedicated to the preservation and protection of objects of historical and personal value made from silver. When applied to cultural heritage this activity is generally undertaken by a conservator-restorer.

Contents

Historically, objects made from silver were created for religious, artistic, technical, and domestic uses. The act of conservation and restoration strives to prevent and slow the deterioration of the object as well as protecting the object for future use. The prevention and removal of surface tarnish is the primary concern of conservator-restorers when dealing with silver objects.

Use of silver

Silver is a precious metal that has been mined for use as early as 4000 BC in Anatolia (Modern Turkey). [1] Because silver is malleable and durable it has been used for many purposes which include jewelry, tableware, ornaments, coins, musical instruments and movie film. It is often used as a plating on other metals.

Tarnish

All metals, apart from pure gold, will corrode naturally when exposed to certain chemicals which can be present in air. [2] High relative humidity, moisture, and air pollutants are common causes of corrosion in metals, including silver. [3] Silver is known in the chemistry world as a noble metal, which means it is resistant to corrosion, but not completely immune. Whether silver plating or pure silver, the composite of the metal will tarnish when exposed to air and sulfur.

Tarnish is a chemical reaction on the surface of metal (copper, brass, silver, etc.) and causes a layer of corrosion. In the case of silver tarnish, the silver combines with sulfur and forms silver sulfide (Ag2S), which is black. The original silver surface can be restored if the layer of silver sulfide is removed. [4] On some metals, tarnish serves as a protective layer known as a patina and is typically found on copper and bronze roofing, architectural elements, statues and bells.

Collections care

Storage and handling

Proper handling, storage, and treatment can help prevent deterioration of silver objects. [3] Metals are best conserved when stored in an even and low humidity atmosphere, ideally at 40% relative humidity or lower. [5] Silver tends to corrode easily when stored in damp, moist locations such as a basement because it will accelerate tarnishing. Some storage boxes contain materials, such as wood, acidic paper, rubber, and adhesives, that can off-gas corrosive materials. Conservators wear nitrile gloves when handling silver to prevent oils, ammonia, and salts from the skin from corroding the surface. [6]

Preventing interaction with sulfur gases

Sulfur-containing gases and particulates can tarnish the surface of silver. These corrosive agents can come from air pollution, paints, textiles, bacterial by-products, and other chemically treated objects or building materials. When storing silver, museum conservators wrap silver in sulfur-free tissue paper and store in a tight sealed polyethylene bag. Activated charcoal is sometimes used to absorb sulfur by placing it in the bag but not in direct contact with the object. Likewise, Pacific Silver Cloth has also been used by museums to prevent tarnishing. [7]

Lacquering

Lacquering is the process of creating a hard durable finish on the surface of an object such as wood or metal. Polished silver is sometimes lacquered to protect against tarnish and to prevent over-polishing. There are different types of resins that are used such as Acryloid B-72 and Incralac. If silver pieces are being displayed in the open, such as in a house or museum exhibit case, it is difficult to prevent corrosion from air exposure. A surface coating will prevent or slow tarnishing and is a service done by professionals or conservator. [8] One of the most used coatings is Agateen. [9]

Lacquer is applied to a surface that has been cleaned with ethanol, acetone, or methyl ethyl ketone. Oils from human hands prevent the lacquer from adhering to the silver. Agateen No. 27 (cellulose nitrate) and Paraloid B-72 are the most commonly used lacquers however there is a debate which lacquer, cellulose nitrate or acrylic, is best. [10]

Historic methods of treating silver

The art of crafting objects out of silver, also known as silversmithing, has been around for centuries. With the creation of hand-made silver objects, the issue of cleaning and caring for these items was a concern. Silversmiths would give advice to clients on how to properly care for their silver. Here are examples of instructions given by silversmiths in the 17th and 18th centuries.

1737 – "Clean it now and then with only warm water and soap, with a Spunge, and then wash it with clean water, and dry it very well with a soft Linnen cloth, and keep it in a dry place, for the damp will spoyle it". [11]
1679 – "...rubb the flagons and chalices from topp to the Bottome, not crosswise, but the Bason and patnes are to be rubb’d roundwise, not acrosse, and by noe means use either chalk, sand, or salt" [11]

Although dated, these instructions are very similar to current methods of cleaning and polishing of silver.

Current practices

The following sections discuss the different methods in which silver objects can be cleaned and polished. Some of the methods described below can cause damage to the surface of the silver, such as scratching or accelerated tarnishing. A conservator should be consulted if there are any questions about the methods below especially when dealing with archaeological, antique or sensitive objects. [12]

Museum conservation practices – historical objects

Water sensitive objects are masked in plastic wrap to avoid getting wet. A slurry of precipitated (pharmaceutical grade) calcium carbonate and deionized water is created and rubbed onto the silver piece with a cotton rag or cotton ball. It is recommended that the slurry be tested on the bottom or in a non-visible area of the silver for abrasiveness. If the slurry is too abrasive it will scratch the surface and increase the potential for future tarnishing. The polish is applied with a soft cloth and polished in a circular motion. [13]

Parts of a silver object from Indianapolis Museum of Art collection, in the process of being polished with calcium carbonate. An unpolished piece is on the left and a finished piece on the right. Unpolished and polished silver artwork pieces.jpg
Parts of a silver object from Indianapolis Museum of Art collection, in the process of being polished with calcium carbonate. An unpolished piece is on the left and a finished piece on the right.

Ethyl alcohol is sometimes added to the slurry mixture to help dry out excess water. The slurry mixture is applied throughout the piece until completely polished. Dark tarnish spots are sometimes located on the surface and may need to be polished more than once to remove. Over polishing is an issue with silver and can cause harm to the surface of the metal. After polishing, the silver object is rinsed in deionized water and dried with a cotton cloth. [12]

Once cleaned and dried the silver is wrapped in acid-free tissue paper and placed in a sealed plastic bag. A 3M anti-tarnish strip is also placed in the bag to absorb any sulfur that may be in the air. The tissue paper is used as a buffer to prevent the silver surface coming into contact with the anti-tarnish strip. [13]

Waddings

Waddings are cloths that have been infused with an organic solvent. Because they contain solvents instead of water, they can be used for polishing metal objects that cannot be exposed to water. Polishing waddings will leave abrasive particles behind and the residue can be removed using a soft brush or by rubbing the surface with a soft linen cloth. [14]

Home / DIY methods

The following sections include home methods that use commonly available household items such as water and salt to clean the surface of silver. Some of the methods use heat which may be dangerous to silver tableware such as candlesticks or knife handles. Water trapped in crevices of silver objects can accelerate tarnishing. [15]

Single Ingredient – Toothpaste is applied with a clean cloth as a gentle abrasive with a soft bristle toothbrush and rinsed in water. [16]

Boiling Water Bath – The silver object or pieces are placed into an aluminum pot and covered with water. One tablespoon of salt and baking soda is added and boiled for three minutes. After cooling, the silver is placed into a warm soapy water mixture and cleaned with a cotton cloth and then dried with a separate cotton cloth. [16]

Soaking bath – A glass roasting pan is lined with aluminum foil with the dull side facing downwards. The silver is placed atop of the foil and a quart of boiling water is poured over the pieces with two tablespoons of baking soda. The silver soaks for five minutes and is dried with a clean cloth. [16]

Chemical dips

A popular and quick method for polishing silver is the use of chemical dips. Dips work by dissolving the tarnished surface of the silver at a highly accelerated rate. Many dips are made of acids and other agents. Acids are very corrosive and pose a danger to the silver surface as well as to the user. Dips can be harmful to objects with sealed surfaces such as candlesticks, trophies and teapots with hollow components because the chemical could leak into the hollow area and can never be removed. [17] Unlike museum quality polishing, employing a slurry of calcium carbonate and deionized water, dips are quicker and less expensive. However, dips are more abrasive to the surfaces of silver, gold, and other metals. Jeffrey Herman confirms this method damages silver. [18]

Laser cleaning

Can be used. [19] The above process wil naturally lead to the cleaning of silver, which is passed through lasers to remove any dirt and pollutants.

Plasma cleaning

Can be used. [20] [21]

Polishing wheels

Polishing wheels, also known as buffing wheels or polishing mops, use a specific electric tool to physically remove tarnish from the surface rather than chemically as with the calcium carbonate slurry or commercial dips. [22]

Because silver is soft, the surface can be easily cut or scratched. The main buffing type used for silver, gold, and plated objects is Canton flannel. This flannel is made of very soft material and will not scratch the plated, lacquered, or other soft surfaces. [22]

Along with buffing wheels, particular compounds are used to help polish the material. Two main types of compounds used for silver and gold surfaces are red and blue compounds. Red, also known as jeweler's rouge, polishes without any cutting action. The blue compound is a dryer compound and is used with a grease-less wheel that also does not cut or scratch the surface. [22]

Museum conservation practices – Archaeology objects

Hellenistic silver medallion, partly gilt, Miletopoli, 2nd-1st centuries BC, after conservation, Antikensammlung Berlin Miletopoli (oggi mysia in turchia), medaglioni ellenistici in argento, II-I sec ac. 02.JPG
Hellenistic silver medallion, partly gilt, Miletopoli, 2nd–1st centuries BC, after conservation, Antikensammlung Berlin

Archaeological silver objects are particularly sensitive to mistakes in planning or carrying out conservation restoration. The essential problem connected with archaeological silver objects is brittleness. [23] Certain objects, such as those that are completely mineralized, nielloed, or gilt, are particularly problematic. When dealing with archaeological objects, reversible processes, such as the use of Paraloid B-72 glue, are preferred to permanent treatments.

Benzotriazole can be used as corrosion inhibitor for archaeological importance. Suitable protective coatings include Paraloid B-72 (or Paraloid B 67 – soluble in white spirit) and Renaissance Wax.

See also

Further reading

Books

Related Research Articles

<span class="mw-page-title-main">Tarnish</span> Corrosion on outer layer of some metals

Tarnish is a thin layer of corrosion that forms over copper, brass, aluminum, magnesium, neodymium and other similar metals as their outermost layer undergoes a chemical reaction. Tarnish does not always result from the sole effects of oxygen in the air. For example, silver needs hydrogen sulfide to tarnish, although it may tarnish with oxygen over time. It often appears as a dull, gray or black film or coating over metal. Tarnish is a surface phenomenon that is self-limiting, unlike rust. Only the top few layers of the metal react. The layer of tarnish seals and protects the underlying layers from reacting.

<span class="mw-page-title-main">Polishing (metalworking)</span> Abrasive process for creating smooth finished surfaces

Buffing are finishing processes for smoothing a workpiece's surface using an abrasive and a work wheel or a leather strop. Technically, polishing refers to processes that uses an abrasive that is glued to the work wheel, while buffing uses a loose abrasive applied to the work wheel. Polishing is a more aggressive process, while buffing is less harsh, which leads to a smoother, brighter finish. A common misconception is that a polished surface has a mirror-bright finish, however, most mirror-bright finishes are actually buffed.

<span class="mw-page-title-main">Cleaning agent</span> Substance used to remove dirt or other contaminants

Cleaning agents or hard-surface cleaners are substances used to remove dirt, including dust, stains, foul odors, and clutter on surfaces. Purposes of cleaning agents include health, beauty, removing offensive odors, and avoiding the spread of dirt and contaminants to oneself and others. Some cleaning agents can kill bacteria and clean at the same time. Others, called degreasers, contain organic solvents to help dissolve oils and fats.

Conservation and restoration of movable cultural property is a term used to denote the conservation of movable cultural property items in libraries, archives, museums and private collections. Conservation encompasses all the actions taken toward the long-term preservation of cultural heritage. Activities include examination, documentation, treatment, and preventive care, which is supported by research and education. Object conservation is specifically the actions taken to preserve and restore cultural objects. The objects span a wide range of materials from a variety of cultures, time periods, and functions. Object conservation can be applied to both art objects and artifacts. Conservation practice aims to prevent damage from occurring, a process known as 'preventive conservation'. The purpose of preventive conservation is to maintain, and where possible enhance, the condition of an object, as well as managing deterioration risks, such as handling and environmental conditions. Historically, object conservation was focused on the category of fine arts but now many different types of objects are conserved. Each type of object material, typically denoted by organic or inorganic then the specific medium, requires a specialized professional conservator and often requires collaborative work between museum staff, scientists, and conservators.

<span class="mw-page-title-main">Conservation and restoration of ceramic objects</span> Preservation of heritage collections

Conservation and restoration of ceramic objects is a process dedicated to the preservation and protection of objects of historical and personal value made from ceramic. Typically, this activity of conservation-restoration is undertaken by a conservator-restorer, especially when dealing with an object of cultural heritage. Ceramics are created from a production of coatings of inorganic, nonmetallic materials using heating and cooling to create a glaze. These coatings are often permanent and sustainable for utilitarian and decorative purposes. The cleaning, handling, storage, and in general treatment of ceramics is consistent with that of glass because they are made of similar oxygen-rich components, such as silicates. In conservation ceramics are broken down into three groups: unfired clay, earthenware or terracotta, and stoneware and porcelain.

<span class="mw-page-title-main">Conservation and restoration of copper-based objects</span>

The conservation and restoration of copper and copper-alloy objects is the preservation and protection of objects of historical and personal value made from copper or copper alloy. When applied to items of cultural heritage, this activity is generally undertaken by a conservator-restorer.

<span class="mw-page-title-main">Conservation and restoration of iron and steel objects</span>

Iron, steel, and ferrous metals constitute a large portion of collections in museums. The conservation and restoration of iron and steel objects is an activity dedicated to the preservation and protection of objects of historical and personal value made from iron or steel. When applied to cultural heritage this activity is generally undertaken by a conservator-restorer. Historically, objects made from iron or steel were created for religious, artistic, technical, military and domestic uses. Though it is generally not possible to completely halt deterioration of any object, the act of conservation and restoration strives to prevent and slow the deterioration of the object as well as protecting the object for future use. One of the first steps in caring for iron is to examine them and determine their state, determine if they are corroding, and consider options for treatment.

The conservation and restoration of outdoor bronze artworks is an activity dedicated to the preservation, protection, and maintenance of bronze objects and artworks that are on view outside. When applied to cultural heritage this activity is generally undertaken by a conservator-restorer.

<span class="mw-page-title-main">Collections maintenance</span> Daily care of cultural heritage

Collection maintenance is an area of collections management that consists of the day-to-day hands on care of collections and cultural heritage. The primary goal of collections maintenance or preventive conservation is to prevent further decay of cultural heritage by ensuring proper storage and upkeep including performing regular housekeeping of the spaces and objects and monitoring and controlling storage and gallery environments. Collections maintenance is part of the risk management field of collections management. The professionals most involved with collections maintenance include collection managers, registrars, and archivists, depending on the size and scope of the institution. Collections maintenance takes place in two primary areas of the museum: storage areas and display areas.

<span class="mw-page-title-main">Conservation and restoration of outdoor artworks</span>

The conservation and restoration of outdoor artworks is the activity dedicated to the preservation and protection of artworks that are exhibited or permanently installed outside. These works may be made of wood, stone, ceramic material, plastic, bronze, copper, or any other number of materials and may or may not be painted. When applied to cultural heritage this activity is generally undertaken by a conservator-restorer.

<span class="mw-page-title-main">Conservation and restoration of shipwreck artifacts</span>

The conservation and restoration of shipwreck artifacts is the process of caring for cultural heritage that has been part of a shipwreck. Oftentimes these cultural artifacts have been underwater for a great length of time. Without conservation, most artifacts would perish and important historical data would be lost. In archaeological terms, it is usually the responsibility of an archaeologist and conservator to ensure that material recovered from a shipwreck is properly cared for. The conservation phase is often time-consuming and expensive, which is one of the most important considerations when planning and implementing any action involving the recovery of artifacts from a shipwreck.

<span class="mw-page-title-main">Conservation and restoration of wooden furniture</span> Preservation of heritage collections

The conservation and restoration of wooden furniture is an activity dedicated to the preservation and protection of wooden furniture objects of historical and personal value. When applied to cultural heritage this activity is generally undertaken by a conservator-restorer. Furniture conservation and restoration can be divided into two general areas: structure and finish. Structure generally relates to wood and can be divided into solid, joined, and veneered wood. The finish of furniture can be painted or transparent.

<span class="mw-page-title-main">Conservation and restoration of clocks</span> Preservation of tangible objects

The conservation and restoration of clocks refers to the care given to the physical and functional aspects of time measuring devices featuring "moving hands on a dial face" exclusive of watches. Care for clocks constitutes regulating the external environment, cleaning, winding, lubrication, pest-management, and repairing or replacing mechanical and aesthetic components to preserve or achieve the desired state as specified by the owner. Clocks are typically composed of multiple types of materials such as wood, metal, paint, plastic, etc., which have unique behaviors and environmental interactions, making treatment options complex. The materials used and the complexity of clockwork warrant having a Horological Conservator complete the work.

<span class="mw-page-title-main">Conservation and restoration of totem poles</span> Preservation of heritage collections

The conservation and restoration of totem poles is a relatively new topic in the field of art conservation. Those who are custodians of totem poles include Native American communities, museums, cultural heritage centers, parks or national parks, camp grounds or those that belong to individuals. Conservation activities include the historical research and context of totem poles, studying materials and manufacture, performing assessments, documentation and treatments. This field can pertain to conservator-restorers, Native Americans, curators, collection managers, registrars, park rangers and city planners.

The conservation and restoration of lacquerware prevents and mitigates deterioration or damage to objects made with lacquer. The two main types of lacquer are Asian, made with sap from the Urushi tree, and European, made with a variety of shellac and natural resins. Lacquer can be damaged by age, light, water, temperature, or damaged substrate.

<span class="mw-page-title-main">Conservation and restoration of bone, horn, and antler objects</span> Preservation of heritage collections

Conservation-restoration of bone, horn, and antler objects involves the processes by which the deterioration of objects either containing or made from bone, horn, and antler is contained and prevented. Their use has been documented throughout history in many societal groups as these materials are durable, plentiful, versatile, and naturally occurring/replenishing.

<span class="mw-page-title-main">Conservation and restoration of paintings</span> Preservation of heritage collections

The conservation and restoration of paintings is carried out by professional painting conservators. Paintings cover a wide range of various mediums, materials, and their supports. Painting types include fine art to decorative and functional objects spanning from acrylics, frescoes, and oil paint on various surfaces, egg tempera on panels and canvas, lacquer painting, water color and more. Knowing the materials of any given painting and its support allows for the proper restoration and conservation practices. All components of a painting will react to its environment differently, and impact the artwork as a whole. These material components along with collections care will determine the longevity of a painting. The first steps to conservation and restoration is preventive conservation followed by active restoration with the artist's intent in mind.

<span class="mw-page-title-main">Conservation and restoration of lighthouses</span> Preservation of building structures

The conservation and restoration of lighthouses is when lighthouse structures are preserved through detailed examination, cleaning, and in-kind replacement of materials. Given the wide variety of materials used to construct lighthouses, a variety of techniques and considerations are required. Lighthouses alert seagoers of rocky shores nearby and provide landmark navigation. They also act as a physical representation to maritime history and advancement. These historic buildings are prone to deterioration due to their location on rocky outcrops of land near the water, as well as severe weather events, and the continued rise of sea levels. Given these conditions preservation and conservation efforts have increased.

<span class="mw-page-title-main">Conservation and restoration of historic firearms</span> Preservation of heritage collections

The conservation and restoration of historic firearms is preventative care, damage repair, stabilization, replacement of missing components, and potentially the return of the firearm to firing capabilities. It requires an understanding of the different types of historic firearms and knowledge in the care and treatment of organic and inorganic materials, as firearms are composed of many types of materials, from wood to metal, that are fitted together.

<span class="mw-page-title-main">Agents of deterioration</span> Major causes of damage to cultural heritage

The 'ten agents of deterioration' are a conceptual framework developed by the Canadian Conservation Institute (CCI) used to categorise the major causes of change, loss or damage to cultural heritage objects. Also referred to as the 'agents of change', the framework was first developed in the late 1980s and early 1990s. The defined agents reflect and systematise the main chemical and physical deterioration pathways to which most physical material is subject. They are a major influence on the applied practice of conservation, restoration, and collection management, finding particular use in risk management for cultural heritage collections.

References

  1. ↑ "10 History of Silver". The Silver Institute. Retrieved 4 March 2012.
  2. ↑ Roberge, Pierre. "Gold Corrosion". Corrosion Doctors. Retrieved 4 March 2012.
  3. 1 2 Erhardt, David; Charles S. Tumosa and Marion F. Mecklenburg (2007). "Applying science to the question of museum climate". Museum Microclimates. National Museum of Denmark: 11–18.
  4. ↑ "At Home Experiment: Put a Shine on it". SciFun. Archived from the original on 14 May 2011. Retrieved 7 March 2012.
  5. ↑ Bachmann, Konstanze (1992). Conservation Concerns: A Guide for Collectors and Curators . Smithsonian Institution. pp.  132. ISBN   9781560981749.
  6. ↑ Bachmann, Konstanze (1992). Conservation Concerns: A Guide for Collectors and Curators . Smithsonian Institution. p.  69. ISBN   9781560981749.
  7. ↑ Bachmann, Konstanze (1992). Conservation Concerns: A Guide for Collectors and Curators . Smithsonian Institution. pp.  99–101. ISBN   9781560981749.
  8. ↑ Bachmann, Konstanze (1992). Conservation Concerns: A Guide for Collectors and Curators . Smithsonian Institution. pp.  100–103. ISBN   9781560981749.
  9. ↑ Perkins, Beverly (2003). "The De-electrification and Re-electrification of Historic Lighting Fixtures at Winterthur Museum". Journal of the American Institute of Conservation. 6. 42 (3): 457–462. doi:10.1179/019713603806112705. S2CID   109844967 . Retrieved 4 March 2012.
  10. ↑ Wharton, Glenn (Jan 1989). "The Cleaning and Lacquering of Museum silver". Western Association for Art Conservation. 11 (1): 4–5.
  11. 1 2 Cripps, Wilfred (1967). Old English Plate. London: Spring Books. pp. 17–18.
  12. 1 2 National Park Service. "Caring for Silver and Copper Alloy Materials" (PDF). Conserve O Gram. NPS. Retrieved 4 March 2012.
  13. 1 2 Drayman-Weisser, T (1992). Caring for Your Collections. New York: Harry N. Abrams Incorp. pp. 109–121.
  14. ↑ Selwyn, L (2017-09-14). "Care and Tarnish Removal" (PDF). Canadian Conservation Institute. Retrieved 4 March 2012.
  15. ↑ Bachmann, Konstanze (1992). Conservation Concerns: A Guide for Collectors and Curators . Smithsonian Institution. p.  103. ISBN   9781560981749.
  16. 1 2 3 Douglas, Ellen. "All Natural Way to Clean Tarnished Silver". National Geographic. Archived from the original on 5 April 2012. Retrieved 4 March 2012.
  17. ↑ Herman, Jeffrey. "Silver Care". Society of Silversmiths. Retrieved 7 March 2012.
  18. ↑ "Tarn-X Tarnish Remover Review and Other Silver Dips - WARNING!". www.hermansilver.com. Retrieved 7 October 2018.
  19. ↑ SALIMBENI, RENZO (2006). "LASER TECHNIQUES FOR CONSERVATION OF ARTWORKS" (PDF). Institute of Applied Physics “Nello Carrara”- CNR. Retrieved 1 October 2013.
  20. ↑ Schmidt-Otta, K (October 2004). "Plasma-Reduction: Its Potential for Use in the Conservation of Metals" (PDF). Retrieved 1 October 2013.
  21. ↑ "Cleaning treatment of a tarnished Daguerreotype by using the reducing afterglow of an atmospheric plasma". Archived from the original on 2013-09-27. Retrieved 2013-10-01. Accessed 1.10.2013.
  22. 1 2 3 Caswell Electroplating in Miniature. "How to Buff and Polish: An Introduction to Buffing & Polishing". Caswell Inc. Archived from the original on 12 March 2012. Retrieved 7 March 2012.
  23. ↑ Wanhill, R.J.H., 2000, Brittle archaeological silver. Identification, restoration and conservation, Materialen, 16, 30– 5; also NLR Technical Publication NLR.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.