🔥 What I Learned by Building My Own Alcohol Stove — Structure, Combustion, and Design Notes —

🌱 Introduction

In my previous article, I wrote about how excessive YouTube watching gradually made it harder for me to take action.
The turning point — from consuming time to creating time — came when I decided to build something with my own hands: an alcohol stove.

Ironically, the idea itself came from a YouTube video.
(Reference: https://www.youtube.com/watch?v=6xE6Q0P-5Mo)

Around that time, my water heater had broken down — a small inconvenience that turned into the spark for this project.
From there, I moved on to making the video
(https://youtu.be/cpYc1Bq18Yc),
which documents the second-generation version of the stove, refined through lessons learned from my first prototype.

When searching in Japanese on YouTube, most results for “alcohol stove” are product reviews, not DIY builds.
So in this article, I’ll share what I learned by actually making and using one — how it works, and what to be careful about in design and operation.

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🔥 1. Structure and Combustion Phases

The combustion of an alcohol stove can be roughly divided into two stages:

(1) Primary Combustion
When you pour in alcohol and ignite it, the vaporized fuel at the opening begins to burn.
This is the primary combustion stage.

(2) Secondary Combustion
As the stove body heats up, the internal alcohol evaporates, and vapor begins to jet out through the small exhaust holes.
When these vapors catch fire, the stove transitions to secondary combustion.

Most commercially available alcohol stoves use this same principle.
During the secondary phase, the flame becomes stronger and more stable — ideal for boiling water efficiently.
Observing my prototype made these transitions between combustion phases much clearer.

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🧪 2. Combustion Phases and Fuel Level

(1) Primary Combustion
Fill the alcohol so that the liquid surface sits slightly above the lower edge of the upper part.
When ignited, the evaporated alcohol burns and heats the stove body,
which in turn causes internal fuel to vaporize and escape through the exhaust holes.

(2) Secondary Combustion — Pressurized Stage
When vapor escaping from the holes ignites, secondary combustion begins.
The fuel level covers the lower edge of the upper part, creating partial sealing and internal pressure.
This pressurization increases flame strength — perfect for tasks like boiling water.

(3) Secondary Combustion — Depressurized Stage
As fuel is consumed and the level drops, the internal seal weakens and the flame becomes gentler.
This phase produces a softer heat, suitable for maintaining temperature over longer periods.

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🧰 3. Improvements from the Prototype

Based on observations from the first model, I made three key changes in the second-generation design:

(1) Minimizing the Gap Between Upper and Lower Parts
The first prototype had a 2–3 mm gap, which caused long periods of weak, depressurized burning.
The new version reduces this gap to the minimum possible, keeping the stove in a pressurized state for most of the burn time.

(2) Raising the Jet Holes
By placing the exhaust holes closer to the top, I achieved several effects:

• Faster ignition of secondary combustion
• Improved thermal efficiency
• Increased fuel capacity within the same body size

(3) Tilting the Jet Holes Upward
The prototype’s holes were drilled horizontally, allowing heat to diffuse sideways.
In this version, I angled them slightly upward to direct the flames vertically.
Even a small change in angle significantly affected heat transfer efficiency.

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🔧 4. Fabrication and Combustion Test Results

The full making process and burn test can be seen in the video:
https://youtu.be/cpYc1Bq18Yc

Key takeaways from the comparison experiments:

• The new model maintained strong flames from the jet holes much longer than the prototype.
• Combustion continued until just before the flame went out.
• Internal pressure was more stable, leading to steadier heat output.
• The secondary combustion started about twice as fast as the prototype.

With its increased fuel capacity, the new design achieved up to 17 minutes of continuous burning —
a better result than I had expected.

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⚠️ 5. Usage and Safety Notes

1. Use 20–25 ml of methylated spirits (denatured alcohol, methanol-based) per burn.
2. Never refill during combustion — there’s a risk of ignition or melting your fuel bottle.
3. When using a windshield, ensure proper ventilation to prevent oxygen deprivation.
4. Keep at least 5 cm (2 inches) of distance between the stove and the bottom of your pot —
   a helpful design insight suggested by ChatGPT.

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🌾 6. Conclusion: Efficiency Isn’t Everything

The improved stove clearly outperformed the prototype in both power and efficiency.
Yet in practice, the original model still has its charm.

For example, when I grill meat alone in my office on weekends,
high heat is great at first — but gentle heat works better once I add vegetables.
In such moments, controllability matters more than maximum output.

The new model maintains strong flames throughout,
but the prototype’s flame naturally softens — and by lifting the pot once and then placing it back, the flame can be fully extinguished —
which makes it more flexible for slow cooking or heat adjustments.

For campers, one ultra-efficient all-in-one stove might be ideal.
But in everyday life, having different stoves for different moods and purposes feels more natural.

In the end, I realized that true satisfaction comes not from maximizing efficiency,
but from valuing comfort and diversity of choice.

And if ChatGPT’s earlier note — “keep at least 5 cm between the pot and the flame” —
turns out to be accurate, it means my current design still has room for improvement.
That insight alone has become the motivation for the next round of experiments.

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🎥 Related Video

▶️ Building a Homemade Alcohol Stove | A Quiet Moment with Flame