What's the best way to preserve a Jack O'Lantern?

The MyScienceProject people carved a bunch of Jack O'Lanterns and tried to preserve them by various means, from vaseline to a commercial pumpkin-preserving spray ("Pumpkin Fresh!") to bleach solution.

The next day, however, we could no longer deny that the bleach pumpkin had a serious problem. It was listing to the side and fluid was oozing from underneath, and the bottom of the interior was slime covered. We tossed it and turned our attention to the last two survivors. The control pumpkin had several moldy areas inside that didn't seem to be spreading very fast. The Pumpkin Fresh pumpkin, while it had little mold growing on the interior, had developed a soft slimy spot on the bottom, similar to the one that had just eaten its way through the bleach pumpkin. This was going to be interesting. Who would hold out the longest?

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