Make Noble Gas Glass-sealed Tubes in Your Home

The glow of noble gases is a mesmerizing fusion of science and art!

After four weeks of work, I successfully created glass-sealed low-pressure noble gas tubes and built a dedicated circuit to drive them. Throughout the process, I faced many challenges. Here, I’m sharing the simplest and most practical solution for making noble gas glow tubes. As far as I know, this might be the first tutorial available on the internet.

Essential equipment：

vacuum pump（The vacuum level needs to reach at least 0.1 Pa.）

vacuum gauge

vacuum connector

handheld gas torch

Material：

noble gas cylinder

glass tubes

Before you get started, please make sure you understand all the underlying principles:

1.Luminescence of Noble Gases

When subjected to a high-voltage electric field, noble gas atoms can become excited and emit colorful light (known as glow discharge). This phenomenon was once widely used in the neon lights. Generally, the lower the gas pressure, the easier it is to produce a glow discharge.

2.Vacuum

To seal pure, low-pressure gases inside a glass tube, we first need to use vacuum technology to evacuate the air, and then introduce a specific amount of pure noble gas at low pressure. This requires a vacuum pump and a vacuum system. A vacuum system consists of airtight pipelines, and the vacuum pump removes air from the system to create the necessary vacuum environment.

3.Sealing Glass

Glass is an amorphous material that begins to soften at around 800 °C. Once softened, it can be easily shaped and sealed.

A vacuum system is usually composed of several chambers and connectors, which you can think of here as pipelines sealed well enough to maintain a vacuum. It is important to note that ordinary pipes (such as water pipes) are not suitable in this case, as their joints are often too large or their materials tend to adsorb gases, making it impossible to achieve a sufficient level of vacuum.

There are many different standards for vacuum connection. In this project, I chose KF(Klein Flange)-standard connectors, which offer a relatively inexpensive yet sufficiently reliable option. Another advantage of KF fittings is that they can be easily assembled by hand without the need for any tools.

Overall, our vacuum system is a simple three-way pipeline connecting the vacuum pump, the gas cylinder, and the glass tube that needs to be sealed. Several valves and pressure gauges are also installed along the system.

1. First, connect the gas cylinder, vacuum pump, and glass tube to the system.
2. Keep the valve at the gas cylinder closed, and open the valve at the vacuum pump. The vacuum pump will start evacuating air from the system.
3. After some time, you can observe from the pressure gauge that the air has been fully evacuated.
4. At this point, close the valve at the vacuum pump and slowly open the valve at the gas cylinder, allowing the noble gas to gradually fill the system. Adjust the flow until the pressure stabilizes at around 100 Pa.
5. The glass tube is now filled with low-pressure pure noble gas.

While the glass tube is still connected to the system, we can use a Tesla coil to check whether the gas inside has been properly filled. If the glass tube displays the correct color under excitation from the Tesla coil, sealing can proceed.

To seal the glass, a strong flame must be used to heat the glass to above 800°C, at which point the glass will begin to soften. By pulling and squeezing it — feel somewhat like modeling clay — the glass can be sealed.

After sealing, it is important to perform annealing at the sealed joint. The temperature should not be allowed to drop too rapidly, in order to prevent internal stresses from causing the glass to crack.

I created a variety of gas-filled glass tubes, including helium, neon, argon, krypton, xenon, nitrogen, carbon dioxide, hydrogen, oxygen, and air. Under high-voltage excitation, each gas displayed its own distinct glow.I named this project Lumora — a combination of "luminous" and "aurora." Since many friends were interested in this gadget, I also launched a crowdfunding campaign on Kickstarter. To preserve them properly, I even had a custom box made. This has been my favorite project of the year.