Candles can expire and go bad, although not the same way as food expires. There are several things to consider when buying a candle, especially how long of a shelf life it has.
Candles Can Expire
Two common ways that a candle expires or goes bad is with color fading and diminishing scent. Some candle waxes hold their color longer than others, and some scents will remain fresh longer than others. You must know what ingredients are in the candle to determine how long of a shelf life it will have.
Some of the things that contribute to the deterioration of a candle include UV light, environmental temperature, how you store it, any chemical additives, type of scents and fragrances, and type of wax. There isn't any danger in lighting older candles, but these various contributing factors could impair the candle burn time and scent throw.
Scented Candle Fragrance Decreases
Most candles scented with essential oils will last for about a year if properly stored in an airtight container and depending on other additives. Essential oils dissipate faster than fragrance oils, which can last for two or more years if stored in an airtight container. It's always a good idea to use your candle within one year of purchase to ensure you get the best throw.
Properties of Different Candle Waxes
While it is true that candle wax doesn't expire, it can deteriorate and weaken. If you leave a colored candle on a window sill, the UV light will break down the colorant, and the candle will fade. Heat can break down candle fragrances, too.
Paraffin is a petroleum based wax, so it has a long shelf life. The conservative estimate is five years, but many paraffin candles last much longer. If the candle is colored and scented, then both of these properties could fade over time. Most candle fragrances are best when burned no later than one-year after purchasing. Store your candle in an airtight container in a cool, dry place. Keep it out of direct sunlight to prevent the color from fading.
Beeswax is a natural wax and has the longest shelf life of all candles. In fact, it's believed that beeswax candle can be kept indefinitely. Many people argue that beeswax candles never expire and point to the Egyptians' use of honey. Sometimes the Egyptians used honey for the embalming fluid and the beeswax to seal the sarcophagus. It is true that honey never spoils, but to keep your beeswax candles looking like new, you want to store them properly in 100% cotton or tissue paper. Make sure to store your candles away from direct sunlight.
Soy wax is an organic material made from soybeans. Just as soybeans can go rancid and rot, so can soy wax. While you can use various additives to prolong the life cycle of a soy candle, if the candle is scented, the fragrance could counter the additive. The chemical reactions, especially over time, could even hasten the deterioration and breakdown of the soy candle. Soy candles will typically have a 1-2 year shelf life. Many soy candles come as a jar candle. If your candle has a lid, then keep it sealed until you're ready to burn it to ensure you get the best throw and burn time.
Palm wax is another natural wax. However, unlike soy wax, it doesn't break down quickly since palm wax has a higher melting point. It's because of the large crystal molecular structure of palm oil that the wax clings longer to the oil fragrances. In addition, the wax's higher melting point allows for the fragrance to have a better throw that's released at a slower rate over a longer period. All of these factors give palm wax candles a longer shelf life than soy wax candles. A palm wax candle should last between 2-3 years.
Gel candles aren't wax, but a polymer resin. The melting point is much higher than waxes, which gives this type of candle a longer burn time. The degradation of the gel candle is less. If you decide to store it, keep it in a cool dry place out of direct sunlight. If your candle didn't come with a lid, then you can either place it in a self-sealing plastic bag or cover the jar with plastic wrap. These candles can last for several years. If the candle is scented, then you should consider how the fragrance might react with the polymer resin and mineral oil over time.
Candles Can Go Bad
Candles can go bad when the color and scent are off due to UV light deterioration, heat, and chemical reactions of candle ingredients. When you know how long different candle waxes retain these attributes, you can choose candles based on their projected shelf life.