What causes jewelry to tarnish

What is Jewelry Tarnish?

Jewelry tarnish is the dull, discolored, or blackened film that appears on the surface of metal jewelry. It's not rust, which typically affects iron and steel. Tarnish is a chemical reaction that occurs when certain metals come into contact with elements in their environment. This reaction forms a compound on the metal's surface, altering its appearance.

The Primary Culprit: Sulfur

The most frequent cause of jewelry tarnish is exposure to sulfur compounds. Sulfur is present in the air, especially in polluted urban environments, as well as in certain natural substances and even some everyday items. When sulfur comes into contact with metals like silver, copper, and brass (which are common in jewelry), it reacts to form metal sulfides. For example, silver reacts with hydrogen sulfide (H₂S) in the air to create silver sulfide (Ag₂S), a dark, flaky layer that is characteristic of tarnished silver.

Sources of sulfur that can cause tarnish include:

• Air pollution: Industrial emissions and vehicle exhaust often contain sulfur dioxide (SO₂).
• Natural gas: Natural gas often has sulfur added as an odorant.
• Rubber: Many rubber products, such as bands, gloves, and even some jewelry boxes, contain sulfur compounds.
• Certain foods: Foods like eggs, onions, garlic, and mustard contain sulfur compounds that can transfer to jewelry if handled without washing hands.
• Wool: Wool fibers also contain sulfur.

Oxidation: Another Contributor

While sulfur is the primary cause for many types of jewelry, oxidation also plays a role, particularly for metals that are less resistant to corrosion. Oxidation is a chemical reaction where a metal loses electrons, typically by reacting with oxygen. This process can lead to a dulling or discoloration of the metal. For example, copper and brass can oxidize over time, developing a greenish or dark patina.

The Role of Moisture and Humidity

Moisture acts as a catalyst for many chemical reactions, including tarnishing. When jewelry is exposed to high humidity or comes into contact with water, the chemical reactions that lead to tarnish can occur more rapidly. Sweat, for instance, is a significant source of moisture and can also contain salts and acids that accelerate the tarnishing process, especially on the underside of rings or bracelets.

Chemicals in Everyday Products

Many common household and personal care products contain chemicals that can react with jewelry metals and cause them to tarnish. These include:

• Perfumes and Colognes: Many contain alcohol and other chemicals that can degrade metal finishes.
• Lotions and Creams: These can leave residues on jewelry that react with the metal or trap moisture.
• Hair Sprays: Similar to perfumes, hair sprays contain various chemicals that can affect jewelry.
• Cleaning Products: Harsh chemicals found in household cleaners are particularly aggressive and can cause rapid tarnishing or even damage to certain metals.
• Chlorine: Found in swimming pools and some cleaning agents, chlorine can react strongly with metals like gold and silver, causing significant discoloration.

Body Oils and Sweat

Our skin naturally produces oils and sweats. While these are generally harmless, they can contain compounds that, over time, react with jewelry metals. The salts and acids present in sweat can accelerate corrosion and tarnishing, particularly in warmer climates or during physical activity. The oils can also trap dirt and other tarnishing agents against the metal's surface.

Factors Affecting Tarnish Rate

The rate at which jewelry tarnishes depends on several factors:

• Metal Type: Sterling silver and copper-based alloys (like brass and bronze) are more prone to tarnishing than gold, platinum, or rhodium-plated jewelry. Pure gold and platinum are highly resistant to tarnish.
• Environmental Conditions: Areas with higher humidity, air pollution, and industrial activity will generally see faster tarnishing.
• Storage: Improper storage, such as leaving jewelry exposed to air or in humid environments, will accelerate tarnishing.
• Contact with Substances: Frequent contact with sulfur-rich materials, chemicals, or even skin over extended periods will increase the likelihood and speed of tarnishing.

Understanding these causes is the first step to preventing and mitigating jewelry tarnish, helping to keep your treasured pieces looking their best.