Many beekeepers are dismayed to find a whitish coating on their beeswax. The powdery substance may occur on blocks of rendered beeswax and candles, or it may arise on foundation, stored combs, or on honeycomb cappings. Sometimes it is snow white, and at other times it appears faintly purple or mauve. Beekeepers wonder if the honey is safe to eat and if the comb can be reused in a hive.
While mold can and does grow in beehives, especially when a colony has died, not all powdery white films are mold. In fact, it is usually just wax bloom—a normal and harmless substance that comes from the wax itself.
Rising to the surface
Beeswax is composed of many different chemicals, including esters of fatty acids and long-chain alcohols. In storage, some of the oils, especially those with a lower melting point, migrate to the surface and crystallize. The tiny crystals may completely cover the surface and make it appear cloudy, fuzzy, powdery, or moldy. In the trade, this substance is known as wax bloom or just bloom.
The way the beeswax was cooled affects the rate of bloom. Beeswax that is cooled quickly takes longer to bloom, perhaps a year or more. But beeswax that is allowed to cool slowly at room temperature may bloom within a few months. In theory, the longer cooling time gives the low-melting point components time to start their migration to the surface before the wax hardens.
Wax bloom is harmless
Wax bloom is completely harmless to both humans and bees. Unless you have mold allergies, most mold that grows in a beehive is also harmless, and even very moldy frames can be quickly scrubbed clean by a healthy colony.
The downside of mold on honeycombs is that it can give the honey an “off” or musty flavor. If you are unsure which one you have, smell it. Wax bloom smells like beeswax, whereas mold smells and tastes like mildew. If you’ve tasted moldy bread or the moldy eye of a potato, you know the sensation.
Removing the bloom
Because wax bloom is made from low-melting point components of beeswax, it has—you guessed it—a lower melting point than the rest of the wax. Beeswax generally melts at about 143-147 degrees F (62-24 degrees C). Wax bloom melts right around 102 degrees F (39 degrees C).
From a practical point of view, the difference in melting points means you can easily remove the bloom. If you leave your beeswax in a sunny location, the bloom will melt much sooner than the wax. In fact, it just disappears. You can also remove it with a blow dryer on a gentle setting.
Using bloom to your advantage
Some people, especially candle makers, take advantage of bloom. If you have a candle with an intricate pattern, you can simply wait for it to bloom and then wipe the surface with a soft rag. This removes the bloom from the high spots but leaves it in the low spots which showcases the design.
A persistent rumor insists that you can tell 100% beeswax from paraffin because paraffin won’t bloom. Unfortunately, it’s not that simple. Some grades of paraffin also contain low-melting point components which will bloom, and others do not. Just remember that the appearance of bloom does not completely rule out paraffin, so don’t use that characteristic to determine purity.
First, decide what it is
I get the feeling that tons of beeswax gets tossed every year for no good reason. If you have frosty-looking frames of foundation or drawn comb, they can be used for bees regardless of whether they sport wax bloom or mold. Bees are good at removing mold and don’t care about bloom.
If the coating appears on honeycomb that you want to extract, take the time to decide what it is. If it turns out to be bloom, you can proceed as normal. But if it is mold, you’ll want to take steps to avoid flavoring the honey.
Honey Bee Suite