How to Keep a Jack-o'-Lantern from Rotting

How to Keep a Jack-o'-Lantern from Rotting

Here is a fun, seasonal science fair project that examines various ways of keeping a carved pumpkin fresh. Can you determine the best way to keep a Halloween jack o lantern from rotting?


The purpose of this project is to see whether or not treating a Halloween jack-o'- lantern, or any carved pumpkin, will help keep it from rotting.


The hypothesis (because it's the easiest to disprove) is that treating a Halloween jack-o'-lantern will not keep it from rotting any better than doing nothing at all (the control).

Experiment Summary

This is a great fall science fair project since pumpkins are readily available from late summer through winter. You could conduct a similar project during the spring using another variety of produce. Since nothing lasts forever, a good timeframe for collecting data is 2 weeks. If all of your pumpkins rot before then, you may choose to end the data collection phase of this project sooner. Since temperature plays a part in the shelf life of a jack-o'-lantern, it's possible your pumpkins may last several weeks if kept in cool conditions. If this is the case, your project may run for a month. Keep the time and temperature in mind when planning your science project.


The main materials for this project are freshly carved jack-o'-lanterns and various pumpkin preservatives. The most commonly applied preservatives are bleach solution, borax solution, petroleum jelly, hairspray, white glue, and commercial pumpkin preservative (if available). You can test any or all of these, plus more if you can think of other preservatives. You will need pumpkins for every method you test, plus a control pumpkin, which will be carved, but untreated.

Experimental Procedure

  1. Carve your jack-o'-lanterns. It helps if you give them different faces so they are easy to tell apart. Try to scrape as much pumpkin goo as possible from the inside of the jack-o'-lanterns so they will be easier to treat with chemicals.
  2. Leave your control pumpkin alone. Apply the treatments to the other pumpkins. Either photograph the pumpkins or write down your observations about the appearance of each jack-o'-lantern.

Pumpkin Treatments

  • Bleach Solution - Mix up enough bleach in water (2 teaspoons bleach per gallon of water) to fill a bucket or tub big enough to submerge your pumpkin. Immediately after carving the pumpkin, soak it in the bleach solution for 8 hours or overnight. Drain the pumpkin and allow it to dry. Each day, spritz the outside and inside of the pumpkin with bleach solution.
  • Borax Solution - Mix up a solution of borax in water (probably 1 teaspoon per gallon) and apply it the same way as you would use the bleach solution.
  • Petroleum Jelly - Smear petroleum jelly (e.g., Vaseline) all over the cut surface of the pumpkin. Reapply once a day if necessary.
  • White Glue - Smear non-toxic white school glue all over the carved pumpkin and allow it to dry.
  • Hairspray - Spray the carved pumpkin, inside and outside, with hairspray. You can reapply the hairspray daily, or not, as you prefer.
  • Commercial Pumpkin Preservative - Follow the instructions on the container.


  1. You can use these methods of applying pumpkin treatments or else you can come up with your own ideas.
  2. Each day, take a photo of the pumpkin and describe its appearance. Is mold present or absent? Is there any shriveling? Is the pumpkin getting soft or smelly or showing any other indications of rotting?
  3. Continue collecting data until the pumpkins have rotted. Discard the rotten pumpkins.


The data for this project will be your photographs and observations regarding the appearance of each pumpkin.


Make a table that shows time in days and whether each pumpkin showed mold, shriveling, or rot. You can indicate the degree of each condition by assigning a numerical value to it, if you like (e.g., 0 = no mold, 1 = slight mold, 2 = moderate mold, 3 = totally moldy).


Was the hypothesis supported? Did the control pumpkin rot at the same time as all of the other pumpkins?

Things to Think About

  • If you want a more complex experiment, add temperature as a factor. This will require additional pumpkins. Leave one of each type of pumpkin at room temperature. Refrigerate one of each type of pumpkin or (since that would take a lot of space) leave one of each type of pumpkin in a hot environment.