The Oddy test is a procedure created at the British Museum

British Museum

The British Museum is a museum of human history and culture in London. Its collections, which number more than seven million objects, are amongst the largest and most comprehensive in the world and originate from all continents, illustrating and documenting the story of human culture from its...

 by conservation scientist Andrew Oddy in 1973, in order to test materials for safety in and around art objects.
Often, materials for construction are evaluated for safety. However, though materials may be safe for building purposes, they may emit faint amounts of chemicals that can harm art objects over time. Acid

Acid

An acid is a substance which reacts with a base. Commonly, acids can be identified as tasting sour, reacting with metals such as calcium, and bases like sodium carbonate. Aqueous acids have a pH of less than 7, where an acid of lower pH is typically stronger, and turn blue litmus paper red...

s, formaldehyde

Formaldehyde

Formaldehyde is an organic compound with the formula CH2O. It is the simplest aldehyde, hence its systematic name methanal.Formaldehyde is a colorless gas with a characteristic pungent odor. It is an important precursor to many other chemical compounds, especially for polymers...

, and other fumes can damage and even destroy delicate artifacts if placed too close.

Procedure

This test calls for a sample of the material in question to be placed in a container with three coupons of different metals - silver

Silver

Silver is a metallic chemical element with the chemical symbol Ag and atomic number 47. A soft, white, lustrous transition metal, it has the highest electrical conductivity of any element and the highest thermal conductivity of any metal...

, lead

Lead

Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

, and copper

Copper

Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...

. The container is sealed with a small amount of de-ionized water to maintain a high humidity

Humidity

Humidity is a term for the amount of water vapor in the air, and can refer to any one of several measurements of humidity. Formally, humid air is not "moist air" but a mixture of water vapor and other constituents of air, and humidity is defined in terms of the water content of this mixture,...

, then heated at 60 degrees Celsius

Celsius

Celsius is a scale and unit of measurement for temperature. It is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...

 for 28 days. An identical container with three metal coupons acts as a control

Scientific control

Scientific control allows for comparisons of concepts. It is a part of the scientific method. Scientific control is often used in discussion of natural experiments. For instance, during drug testing, scientists will try to control two groups to keep them as identical and normal as possible, then...

. If the metal coupons show no signs of corrosion

Corrosion

Corrosion is the disintegration of an engineered material into its constituent atoms due to chemical reactions with its surroundings. In the most common use of the word, this means electrochemical oxidation of metals in reaction with an oxidant such as oxygen...

, then the material is deemed suitable to be placed in and around art objects. The Oddy test is not a contact test, but is for testing off-gassing

Outgassing

Outgassing is the release of a gas that was dissolved, trapped, frozen or absorbed in some material. As an example, research has shown how the concentration of carbon dioxide in the Earth's atmosphere has sometimes been linked to ocean outgassing...

.

Each metal detects a different set of corrosive agents. The silver is for detecting reduced sulfur compounds and carbonyl sulfides

Carbonyl sulfide

Carbonyl sulfide is the chemical compound with the formula OCS. Commonly written as COS, it is a colourless flammable gas with an unpleasant odor. It is a linear molecule consisting of a carbonyl group double bonded to a sulfur atom...

. The lead is for detecting organic acids, aldehyde

Aldehyde

An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....

, and acidic gases. The copper is for detecting chloride

Chloride

The chloride ion is formed when the element chlorine, a halogen, picks up one electron to form an anion Cl−. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. The chloride ion, and its salts such as sodium chloride, are very soluble in water...

, oxide, and sulfur compounds.

There are many types of materials testing

Materials testing

The following are organizations and other resources involved in testing of materials.* ASTM International* Bundesanstalt für Materialforschung und -prüfung* European Reference Materials* Nadcap* Zwick Roell Group...

 for other purposes, including chemical testing

Chemical test

In chemistry, a chemical test is a qualitative or quantitative procedure designed to prove the existence of, or to quantify, a chemical compound or chemical group with the aid of a specific reagent...

 and physical testing

Physical test

A physical test is a qualitative or quantitative procedure that consists of determination of one or more characteristics of a given product, process or service according to a specified procedure...

.

Development

The Oddy test has gone through many changes and refinements over time. Whereas Andrew Oddy proposed to place each metal coupon in a separate glass container with the material to be tested,
Bamberger et al. proposed a "three-in-one" test, where all three metal coupons shared one container, simplifying the procedure. Robinett and Thickett (2003) refined the "three-in-one" test by stabilizing the metal coupons.
Institutions that use the Oddy test in their research are mainly art museums such as The J. Paul Getty Museum

J. Paul Getty Museum

The J. Paul Getty Museum, a program of the J. Paul Getty Trust, is an art museum. It has two locations, one at the Getty Center in Los Angeles, California, and one at the Getty Villa in Pacific Palisades, Los Angeles, California...

, The Nelson-Atkins Museum of Art

Nelson-Atkins Museum of Art

The Nelson-Atkins Museum of Art is an art museum in Kansas City, Missouri, known for its neoclassical architecture and extensive collection of Asian art....

, and the Metropolitan Museum of Art

Metropolitan Museum of Art

The Metropolitan Museum of Art is a renowned art museum in New York City. Its permanent collection contains more than two million works, divided into nineteen curatorial departments. The main building, located on the eastern edge of Central Park along Manhattan's Museum Mile, is one of the...

.