Money does not dissolve in water. The materials used to produce currency, from the fibers in bills to the alloys in coins, are specifically chosen to resist dissolution. While a trip through the washing machine or an accidental drop in a puddle will not turn cash into a liquid solution, water can still cause significant physical damage. Understanding how money resists dissolving and how it reacts to moisture can help you protect your currency.
Defining Dissolution
Dissolution is a chemical process where a solid (solute) breaks down on a molecular level and disperses uniformly into a liquid (solvent) to form a solution. This requires the solvent molecules to have a stronger attraction to the solute molecules than the solute molecules have for each other. Water is an excellent solvent for polar substances like salt or sugar because it is highly polar. However, water is a poor solvent for the non-polar organic and metallic compounds used in currency. When currency is exposed to water, the water molecules cannot overcome the strong intermolecular forces holding the material together, preventing true dissolution.
The Reaction of Paper Bills to Water
United States paper currency is not made from wood-pulp paper. It is composed of a durable blend of approximately 75% cotton and 25% linen fibers, making it more akin to a fine fabric. This composition allows bills to survive accidental washing with relatively little structural harm. The long, interwoven natural fibers of cotton and linen are highly resilient to water exposure compared to the shorter cellulose fibers found in wood pulp.
However, the bill is not waterproof, and water exposure causes physical changes that compromise its integrity. Water weakens the bonds between the fibers, making the bill limp and susceptible to tearing and abrasion. Prolonged submersion or excessive scrubbing can cause the embedded red and blue security threads and microprinting to lift or become obscured. The specialized inks, while designed not to run, can still bleed or smear if the bill is handled too roughly while wet.
The Reaction of Coins to Water
Coins, made of metal alloys, are insoluble in water but are susceptible to corrosion. Corrosion is an electrochemical reaction where the metal reacts with oxygen and moisture to form a more chemically stable compound. For example, modern U.S. pennies are primarily zinc with a thin copper plating. If water breaches the copper, the underlying zinc can corrode quickly.
The speed and extent of corrosion depend on the alloy and the water’s composition. Saltwater accelerates this process because chloride ions increase the solution’s conductivity, making it more corrosive than plain tap water. Metals like copper and nickel, common in coins, form a thin layer of oxidation when exposed to air and water. This greenish patina on copper actually serves as a protective barrier against further decay. Rust is a form of corrosion limited to metals containing iron and does not typically affect modern circulation coins.
Practical Steps for Salvaging Wet Currency
If paper currency becomes wet, the safest method for salvaging it is gentle air-drying. Separate the bills and lay them flat on an absorbent surface, such as a clean towel, in a dry room with good air circulation. Using a fan on a low setting can speed up the process. Avoid direct, high heat sources like a microwave or oven, as these can scorch the paper or damage the security features.
For coins, simply wiping them gently with a soft cloth to remove moisture and surface debris is usually sufficient. Avoid harsh chemicals or abrasive scrubbing, which can remove the protective patina layer and reduce the coin’s value. If currency is severely damaged, such as being stuck together or if more than half of the bill is unrecognizable, you can submit a claim to the Bureau of Engraving and Printing (BEP) for possible redemption. Local banks may also accept wet or soiled cash and handle the exchange process.