Best Methods for Preserving a Pumpkin Using Diatomaceous Earth


One of the most important traditions for Halloween is carving a pumpkin. There are thousands of videos and articles available online with information on the best way to carve a pumpkin, but surprisingly few sources of information on the best way to preserve them.

There’s nothing worse than carving a few pumpkins early only to have them looking drab, shabby and overripe come Halloween night.

In this article, we’ll provide a comparative study of the most popular preservation methods to help you decide on the best way to keep your creepy pumpkins looking fresh and spooky for the entire lead-up to Halloween.

Choosing The Best Pumpkin For Carving

When it comes to Halloween, not all pumpkins are created equal. Cornell University Horticulturalist Steve Reiners suggest the best strategy is to find a pumpkin with a strong stem.

A weak step is an indicator of over ripeness, meaning that rotting is likely already underway. A strong stem is able to provide the pumpkin with nutrients long after harvest, making it last longer and preserving the color.

Choosing the right pumpkin is integral in ensuring your pumpkin will be easy to carve and retail structural integrity for the duration of the Halloween period.

If you do accidentally purchase a pumpkin that has either a rotting stem or rotting top, be sure to cut the damaged area off as soon as possible to prevent the spread of rot.

Do Pumpkin Preservation Methods Actually Work?

The sheer amount of conflicting information available online with regards to pumpkin preservation can make it difficult to determine exactly which methods work and which methods don’t.

One of the best sources of information on the various different preservation methods is, who ran a comprehensive study on the subject. Using seven different methods, the MyScienceProject team measured mold penetration, structural integrity and more to determine which method was superior.

All of the pumpkins used in the study weighed an average of 2.5 pounds and were kept in a room with a temperature between 62 and 64 degrees fahrenheit. Observations were recorded over a period of 14 days.

Method 1: White Glue

Coating the inside of a pumpkin with white PVA glue is a common technique for preserving pumpkins. Much of the rot that occurs in Halloween pumpkins is caused by airborne bacteria and germs. The principle behind this technique is that the glue will seal the pumpkin and protect it from rot, dehydration, oxidation and airborne pathogens.

The white glue coating method yielded poor results when compared to most of the other techniques. After just 48 hours, the pumpkin began to show signs of reduced structural integrity, softening and mold.

After just six days the pumpkin had softened significantly and was covered in mold spots. This acceleration of decay could have actually been caused by the PVA glue coating, as it could potentially allow existing mold and bacteria to take advantage of sealed-in moisture.

Method 2: Vaseline

The vaseline preservation method is similar to the white glue technique, as it is designed to prevent airborne bacteria from colonizing the pumpkin. Vaseline is used to coat the inside of the pumpkin.

Similarly to the PVA white glue application, this technique actually locks in moisture for bacteria to feed on. After just 48 hours, the vaseline pumpkin began to grow mold, and by day six was colonized by a large amount of white mold.

Between day 6 and day 10 the pumpkin became completely covered in mold and had to be discarded. Like white glue, vaseline is inefficient and ineffective in preserving pumpkins for Halloween.

Method 3: Bleach

Bleach is a powerful antimicrobial substance that is able to kill most forms of bacteria. In this experiment, the pumpkin was soaked in a solution consisting of 1 teaspoon of bleach per gallon of water for several hours after carving.

While this process hydrates the pumpkin and prevents mold and bacteria from colonizing the pumpkin, it bleaches away much of the color of the vegetable, leaving it pale and unhealthy-looking.

The bleach-soaked pumpkin retained structural integrity and remained mold free for the duration of the experiment, but the harsh chemicals used to preserve it cause it to become slimy and soften by day 8. This pumpkin was discarded on day 11 of the trial.

While bleach is effective in preventing decay and mold colonization, it can discolor a pumpkin and requires the use of toxic chemicals that can be harmful if inhaled.

Method 4: Acrylic Spray

Acrylic spray is another popular technique online. The pumpkin is sprayed with an acrylic aerosol that is intended to seal the pumpkin from contaminants and pathogens.

Similarly to the white glue and vaseline preservation techniques, this method seals in bacteria and moisture, causing the pumpkin to decay in just two days. By day eight, the pumpkin became completely covered in mold and had to be discarded.

Method 5: Pumpkin Fresh Preservative Spray

Pumpkin Fresh is a purpose-formulated retail spray that is designed to preserve pumpkins for Halloween with a biodegradable composition.

With a proprietary formula that claims to prevent decay, rot, and mold, Pumpkin Fresh is one of the only products that is specifically designed for Halloween pumpkins.

The efficacy of Pumpkin Fresh as a pumpkin preservative is on par with the bleach preservation technique. A pumpkin sprayed with Pumpkin Fresh will retail integrity and freshness for five days, at which point it will begin to slowly develop mold.

Pumpkin Fresh will keep a pumpkin fresh for up to 14 days with minimal rot or mold. Drawbacks to this preservation method are the high cost of the spray, and the aerosol spray delivery method that may irritate eyes and lungs.

Method 6: Chemical-Free All Natural Pumpkin

Surprisingly, an all-natural pumpkin will last far longer than a pumpkin treated with either white glue, vaseline or acrylic spray. Mold will colonize the pumpkin within 3-4 days of carving but grow very slowly, allowing the pumpkin to be used for up to day 14, at which point it will need to be disposed of.

This technique, while as effective as Pumpkin Fresh spray, will vary in efficacy depending on the local weather and humidity. Natural pumpkins will last longer in cold environments, and last less time in hot, humid environments.

Method 7: Diatomaceous Earth

Diatomaceous earth wasn’t used in the MyscienceProject experiment, but offers a number of unique properties that make it a highly effective pumpkin preservative. Diatomaceous earth consists primarily of silica powder, which is highly absorbent.

Filling the inside of a carved pumpkin with diatomaceous earth will cause the silica powder to absorb all of the moisture content of the vegetable without affecting visual appearance.

This technique was highly effective in preventing mold colonization for up to 6 days, at which point the structural integrity of the pumpkin began to fail. By day 14, the pumpkin had begun to completely decay and had to be discarded.

Diatomaceous earth is an effective pumpkin preservative and will allow a pumpkin to last far longer than a natural or glue-coated pumpkin. The advantages of this technique are the lack of chemical preservatives and low cost of diatomaceous earth.

The Verdict

Out of the seven pumpkin preservation methods, only two were viable as long-term pumpkin preservation techniques. White glue, vaseline and acrylic spray all caused the rot of the pumpkin to accelerate.

Pumpkin Fresh spray did not increase the lifespan of a carved Halloween pumpkin beyond that of a natural pumpkin. Only bleach and diatomaceous earth offered a significant improvement in Halloween pumpkin lifespan.

Bleaching pumpkins, although functioning as an effective preservative, requires the use and storage of toxic chemicals and can reduce the visual impact of a pumpkin. Overall, the best treatment to preserve Halloween pumpkins is with diatomaceous earth, which dehydrates and preserves the pumpkin without the need for chemicals.

Pumpkin Carving Alternatives

Carving a pumpkin is the primary cause of rot and decay in Halloween pumpkins. Cutting a pumpkin into a spooky face reveals the decay-prone inner flesh of the vegetable, accelerating the rotting process.

There are a number of different techniques that can be used to decorate a pumpkin for Halloween that don’t require carving. Wrapping a pumpkin in patterned napkin is an effective, fast and easy method of decorating a pumpkin while preserving structural integrity.

Simply dip patterned napkins in water and apply them to the outside of the pumpkin, then allow to dry.

Pumpkins can also be wrapped in burlap or twine for a rustic design, or painted with different colors for an innovative and festive approach that will preserve the lifespan of your Halloween decorations.

Fast Facts About Jack-O-Lanterns

The practice of carving pumpkins into Jack-O-Lanterns for the Halloween period stems back hundreds of years. The origins of Halloween pumpkins are found in the Irish myth of “Stingy Jack”. In the myth, the titular character was said to have invited the devil to drink and didn’t want to pay.

Through some quick thinking and convincing arguments, Stingy Jack convinced the devil to transform into a coin so he could pay for the drinks. Instead of paying, Stingy Jack kept the devil coin in his pocket, locked in place by a silver cross.

The devil, in the form of the coin, eventually bargained with Stingy Jack and convinced him to let him go, which led to a long series of devious agreements and contracts between the two. The tale culminates in Stingy Jack being cursed to wander the earth with a burning coal, which he then placed in a turnip.

This myth led to the carving of vegetables such as turnips, pumpkins, potatoes and beets. Irish immigrants to the United States brought this tradition to the country in the early 18th century, which was subsequently absorbed into the US Halloween tradition. Now Jack-O-Lanterns are an integral aspect of Halloween tradition, carved from over 50 varieties of pumpkins.

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