It’s summer, and one of the best ways to cool off is to jump in a nice refreshing pool with sparkling blue water! But please, take off your jewelry before you do. Not only will this help in keeping your metal and gems sparkly by getting them away from sunscreen and other residues, it will keep them out of certain chemicals that do not get along well with the alloys in gold. Exposure to chlorine or bromine (in bleach or pools, and made worse when the liquid is hot) weakens karat gold, especially lower karat and white gold, but to some degree even in 18k yellow gold.
If you’re interested in the science behind this phenomenon, read on. If not, the long story short is: don’t wear your gold jewelry in the pool or hot tub! It may become brittle and even break. Gold refiner Hoover and Strong did a comprehensive study of different concentrations, temperatures, and alloys, the results of which you can read here.
The higher the concentration, the longer the exposure and the higher the temperature, the faster the deterioration of the [jewelry] settings.
The technical term for what happened to the gold in this study is stress corrosion cracking. As with all matter, the molecules that make up gold jewelry are arranged in a specific structure. The gold atoms and the copper or nickel or other atoms that make up the alloy form what is known as a grain boundary. Normally, the metal is ductile, and so it has the tensile strength and flexibility to be bent and formed without becoming brittle. Reactions with halogen group elements (chlorine, bromine, iodine, fluorine, etc) disrupts these boundaries. Then, when the metal is stressed (for example, prongs are stressed by holding diamonds in place), the already damaged boundaries are separated, and the metal tears apart.
Stress corrosion cracking is obvious in the appearance of the break. It is rough, porous, and grainy as a result of the internal separation of the metal’s structure. Sometimes these breaks (like a broken prong) can simply be repaired and if the jewelry is kept away from the chemical culprits in the future, it may be good for many more years of wear. Occasionally, however, the gold gets so damaged and brittle from exposure that the best option remaining is to remake the entire piece with fresh metal and recycle the old jewelry so the gold can be purified again.
Spread the word and keep your jewelry beautiful by keeping it OUT of the pool and hot tub this summer. If you're reading this too late and your rings have already been exposed to chlorine, take them to your local jeweler for an inspection. Locals, you can contact me via e-mail or Facebook to set up an appointment.