Stick two metal electrodes into opposite ends of a pickle, hook them up to mains electricity, and stand back.

Within seconds, the pickle begins to hiss and steam. Then one end suddenly erupts in a fierce orange glow, as if the vegetable has briefly turned into a lamp.

Special Note: Please don’t try this at home. The demonstration involves exposed mains electricity and can cause severe injury or death.

The “glowing pickle” has been a favorite classroom stunt for decades. The usual explanation is simple: the salty brine conducts electricity, and excited sodium ions produce the orange light. But that’s only part of the story.

After sacrificing more than 100 pickles to science, an electrical engineer at Portland State University believes he is finally closing in on an explanation. And surprisingly, it involves tiny hydrogen explosions.

Joshua Méndez Harper, an assistant professor of electrical engineering, presented the results at the Electrostatics Society of America’s annual meeting in June.

A pickle conducts electricity because its watery interior contains dissolved salt. In water, salt separates into charged particles called ions, which can carry electrical current. A fresh cucumber contains water too, but far fewer dissolved ions, so it conducts much less readily.

So far, straightforward enough. But when electricity starts flowing through a pickle, things get considerably messier.

One classic idea is that the liquid around an electrode heats until some of it boils. The resulting pocket of vapor briefly insulates the electrode. As liquid moves back toward it, electricity can jump across the tiny gap as a spark—something like the tiny electrical discharge that occurs when you touch a doorknob after walking across a carpet.

Another explanation focuses on electrolysis. Passing electricity through water can produce hydrogen gas, providing something combustible inside the pickle.

Méndez Harper thinks the two explanations are connected. The electrical current produces hydrogen gas while also heating the brine enough to create vapor pockets. As those pockets form and collapse, electrical sparks can jump between the electrode and the surrounding liquid. Those sparks, he proposes, ignite the hydrogen.

In other words, the pickle may be hosting tiny bursts of combustion, with electrical discharges providing the ignition.

“There is hydrogen involved, but it’s actually not heat that’s igniting it—it’s the spark,” Méndez said in a statement. “It’s just like why you don’t light a cigarette at a gas station. You’re producing a spark that ignites the gas.”

The idea helps explain why the glow is so sudden and intense. But why does the light usually appear near just one electrode?

Hydrogen production during electrolysis depends on electrode polarity, which could help explain the asymmetry. Earlier experiments have also linked the glow to polarity. For now, however, the precise sequence of events still needs further investigation.

Researchers were putting glowing pickles under scientific scrutiny long before Méndez Harper entered the kitchen.

Scientists have looked at this phenomenon for decades. A 1993 Journal of Chemical Education paper showed that the familiar yellow-orange color corresponds to sodium’s characteristic emission. A later 2005 experiment replaced sodium with other dissolved metals and produced differently colored pickles—including pink, purple, and red glows.

The mystery isn’t really why the light is orange. Scientists have known that for decades. The harder question is what supplies the energy that makes the sodium glow in the first place.

A 2015 study in Physics Education used spectroscopy, temperature measurements and high-speed recordings to show that the phenomenon depended on electrode polarity and involved hydrogen. Its authors argued that the apparently silly demonstration concealed a considerably more complicated interaction between electricity, heat, and chemistry.

Méndez Harper’s experiments build on that work by proposing a more specific trigger: electrical sparks that ignite hydrogen produced inside the pickle.

The sodium still supplies the signature color. When sodium atoms become excited, they release energy as yellow-orange light, much like the sodium compounds used to produce yellow fireworks.

“You’re exciting sodium ions, which produce that characteristic orange glow,” Méndez said. “If you were to pickle something in a different salt, you’d get a color unique to those elements.”

So the glowing pickle isn’t quite a vegetable light bulb, but a tiny, salty plasma experiment—one powered by boiling liquid, electrical breakdown, and combustible gas.

And even after decades of experiments and more than 100 recently sacrificed pickles, scientists still have a few details to figure out.