This is what wax bloom looks like: weird white mold

It can be discouraging to find a white, powdery film covering your rendered beeswax and lovingly crafted candles. But fear not! It may just be wax bloom, something harmless and easy to fix.

Inside: Don’t assume the powdery coating on your beeswax is mold. It may just be wax bloom, a normal, harmless substance that rises to the surface.

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 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 they can reuse the comb in a hive.

While mold can 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.

Oils rising to the surface make bloom

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.

Remove the bloom with heat

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 highlight a design

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 if it’s bloom or mold

I get the feeling that tons of beeswax get 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 a honeycomb 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

This cake of rendered beeswax is several years old and is coated with wax bloom. Note how the bloom enhances the lettering.
This cake of rendered beeswax is several years old and is coated with wax bloom. Note how the bloom enhances the lettering. © Rusty Burlew.

About Me

I backed my love of bee science with a bachelor’s degree in Agronomic Crops and a master’s in Environmental Studies. I write extensively about bees, including a current column in American Bee Journal and past columns in Two Million Blossoms and Bee Craft. I’ve endured multiple courses in melittology and made extensive identifications of North American bees for iNaturalist and other organizations. My master beekeeper certificate issued from U Montana. I’m also an English nerd. More here.

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  • Sage advice Rusty, it would be a crying shame if beeswax were being discarded for this reason.

    I always think it looks a bit like the ‘bloom’ you get on chocolate when kept a bit too warm. This is also fats rising to the surface and is still perfectly edible!

    • Ray,

      When I was writing this, I kept thinking of the bloom on chocolate as well. (I suppose chocolate is never far from my mind.)

  • Thank you so much for addressing this. I have a large block of rendered beeswax that I thought was growing mold on it. I decided to put it in my freezer (since mold won’t continue to grow there) until I figured out what to do with it. Now I know that it’s not mold, just wax bloom!

  • How do you keep bloom from happening? I’ve tried to make primitive 100% beeswax images. I dyed the beeswax with black wax crayons, molded the melted wax and than rubbed the cooled images with cinnamon. They came out perfect, until the bloom ruined all of them. I couldn’t wash off the bloom because of the cinnamon rub. The bloom was slate grey in color and did not enhance the design of the images. Can you cast an image, treat it with some kind of anti bloom spray and then rub the cinnamon on? I really don’t want to mix the beeswax with paraffin wax, if I could avoid it. Any help you can give would be great.

  • I have several blocks of wax that we rendered this year and today, I noticed the white on top. I’m so glad to read what you’ve said and to know that it will still be good for my candle making. Thank you!

  • I have good Flow honey (Austin, Texas) in a glass jar that appears to have penicillin-looking mold floating on surface. Is this honey recoverable & or edible ? Can these ”moldy” looking floaters be strained out & honey recovered?

    • Ronbo,

      Just skim it off the top. The mold will only grow where the air meets the surface of the honey.

  • Hi rusty! Love your knowledge and this site!
    I have honeybees who love to sit on our fish ponds “floating lettuce” .

    Dozens cluster inside the plant. I thought they were collecting stinky water…but for what purpose? Then I thought it had something to do with propolis production.

    Any thoughts?

    • Ellen,

      They were most likely collecting water. A colony uses great quantities of it, especially for cooling the inside of the hive.