# Making Plasma in the Microwave (DD-287)

> Plasma is gas in which enough atoms have lost electrons that it conducts electricity and glows. In a microwave oven, plasma usually starts where the field gets concentrated: at sharp metal edges, or in the gap between two grape halves. A 2019 study in PNAS showed the grape effect comes from the fruit acting as a resonator; water-rich spheres trap the microwaves and build a hotspot where they touch, which ionizes the surrounding air. A match flame can do the same by supplying already-ionized gas. Once started, the plasma absorbs microwave energy, rises as a glowing ball and can damage the oven, so I'd treat it as a demonstration, not a kitchen trick. The footage shows a bright, flickering plasma ball inside an inverted glass in a microwave.

- Department: Science
- First published: 2024-08-02
- Last updated: 2024-08-02
- Permalink: https://detailenjoyer.com/case/making-plasma-in-the-microwave/
- Author: Marcus Easterling (DetailEnjoyer), The Detail Department

## Quick facts

- **DD-287-F01**: Plasma is ionized gas that conducts and glows. _(Write-up · Exhibit A (Ionized gas))_
- **DD-287-F02**: Grape halves can concentrate microwaves enough to spark plasma. _(Write-up · Exhibit B (Concentrated fields))_

## Write-up

A glowing ball of plasma can appear inside a kitchen microwave. In 2019, researchers traced grape plasma to microwaves trapped inside the fruit.

1. **Ionized gas**: Plasma is gas with enough free electrons to conduct electricity and glow.
2. **Concentrated fields**: In a microwave, plasma usually starts at sharp metal edges or between grape halves.
3. **Grapes as resonators**: A 2019 study found grapes trap microwaves and build a hotspot where they touch.
4. **A glowing ball**: Once started, the plasma absorbs microwave energy and glows as a ball.
5. **Hard on ovens**: Microwave plasma can damage the oven, so it's a demonstration, not a kitchen trick.

## Related case files

- [Microwave Metal (DD-589)](https://detailenjoyer.com/case/microwave-metal/): I paired it with the case on why metal sparks in a microwave
- [(Z) Pinch Me (DD-741)](https://detailenjoyer.com/case/z-pinch-me/): I linked more plasma physics
- [Plasma (DD-113)](https://detailenjoyer.com/case/plasma/): I linked a hands-on way plasma forms

## Reel vs. record

- **Note**: 'Typically created by exciting gases into an ionized state': right. I'd add that it usually needs a starter, such as metal edges, a grape pair or a flame, to concentrate the field.

## Video: Making Plasma in the Microwave: A Glowing Ball of Plasma Can Appear Inside a Kitchen Microwave

- Duration: 28.7 s · Published: 2024-08-02
- File: https://detailenjoyer.com/assets/videos/C-MRkHSt75k.mp4

### Transcript

DID YOU KNOW? Plasma in microwaves is typically created by exciting gases into an ionized state. This can happen when a microwave oven's electromagnetic waves interact with metal objects or thin air pockets causing a strong electric field. This field can strip electrons from the atoms of gases present such as oxygen or nitrogen, ionizing them and creating plasma. The process often starts with a small spark which can ionize more gas molecules leading to a chain reaction. This ionized gas emits light which is why plasma in a microwave often appears as a glowing ball or arc. NOW YOU KNOW!

## Questions & answers

**Q: What is plasma?**  
A: Free electrons make it conduct and glow. _(Source: Write-up · Exhibit A (Ionized gas) · Wikipedia: Plasma (physics))_

**Q: Where does microwave plasma usually start?**  
A: Those spots concentrate the field. _(Source: Write-up · Exhibit B (Concentrated fields) · Khattak et al., PNAS (2019): Linking plasma formation in grapes to microwave resonances of aqueous dimers)_

**Q: What did the 2019 study find about grapes?**  
A: The hotspot forms where they touch. _(Source: Write-up · Exhibit C (Grapes as resonators) · Khattak et al., PNAS (2019): Linking plasma formation in grapes to microwave resonances of aqueous dimers)_

**Q: What does the plasma do once started?**  
A: It often rises to the top of the cavity. _(Source: Write-up · Exhibit D (A glowing ball) · Wikipedia: Plasma (physics); Khattak et al., PNAS (2019): Linking plasma formation in grapes to microwave resonances of aqueous dimers)_

**Q: Why not try it at home?**  
A: The plasma can scorch the cavity. _(Source: Write-up · Exhibit E (Hard on ovens) · Khattak et al., PNAS (2019): Linking plasma formation in grapes to microwave resonances of aqueous dimers)_

## Sources

- [Wikipedia: Plasma (physics)](https://en.wikipedia.org/wiki/Plasma_(physics))
- [Khattak et al., PNAS (2019): Linking plasma formation in grapes to microwave resonances of aqueous dimers](https://www.pnas.org/doi/10.1073/pnas.1818350116)

## Cite this case file

Easterling, Marcus. "Making Plasma in the Microwave." The Detail Department (DetailEnjoyer), case file DD-287, last updated Aug 2, 2024. https://detailenjoyer.com/case/making-plasma-in-the-microwave/