Laser Winter Protection: Why You Shouldn’t Use Antifreeze

As winter approaches, your workshop’s laser may not be protected against freezing temperatures. Often, antifreeze is recommended for CO₂ lasers in such cases. Why you should never use it and how to ensure your CO₂ laser survives the cold season are explained in this article about laser winter protection.

In the article Laser Chiller – Which Water Cooling System for My Laser? , we learned that CO₂ laser tubes have two critical temperature thresholds: above 25°C, the tube needs cooling, and below 15°C, it shouldn’t be used. The cooling water in the tube must always be at least 15°C.

At lower temperatures, the gases inside the tube do not activate properly, leading to reduced laser performance. Depending on the humidity, temperatures below 15°C can also bring the laser dangerously close to the dew point, causing condensation inside the tube. Last winter, I faced this very problem, and the first solution I found in forums and Facebook groups was antifreeze.

Windshield antifreeze for cars sounds like a good idea at first. It’s inexpensive, widely available, and depending on the mixture, can prevent freezing down to -40°C. That should be enough, right?

Windshield antifreeze contains the following components:

• Water
• Alcohol/glycol
• Anionic surfactants (!!)
• Color and fragrance additives

The issue with windshield antifreeze lies in the anionic surfactants. These are also found in dish soap, laundry detergent, and shampoo, and are responsible for foam formation. Foam is the last thing you want in a cooling system, as air bubbles in the tube can prevent proper cooling. Additionally, stationary bubbles in the tube can cause temperature stress, potentially cracking the glass.

Another issue with anionic surfactants is their negatively charged functional groups, which can disrupt the passivation layer on metal surfaces, leading to corrosion. This means your water tank could rust from the inside out.

Never use windshield antifreeze in your CO₂ laser cooling system!

If you must use antifreeze in your CO₂ laser, only use car radiator antifreeze. It is made of glycol alcohol (chemically: monoethylene glycol) and sometimes includes anti-corrosion additives. Ethylene glycol has a freezing point of -16°C and boils at 197°C. The primary purpose of radiator antifreeze is to prevent the coolant in car engines from evaporating, which pure water would do.

Tap water freezes at 0°C. Distilled water, however, has a freezing point far below that. Depending on its purity, distilled water can freeze at temperatures as low as -70°C. Unless your workshop is extremely cold, distilled water is more than sufficient for cooling your CO₂ laser. It is also very affordable, costing around €0.40 per liter at hardware stores or supermarkets.

Distilled water is demineralized, meaning it contains no ions or trace elements. This gives it additional benefits:

• Non-conductive: If a spark jumps into the cooling water, it won’t conduct electricity further.
• Non-corrosive: Without charged ions, distilled water won’t cause corrosion or damage metal parts.

Using distilled water in your CO₂ laser’s cooling system leaves the issue of maintaining the minimum operational temperature of 15°C. This temperature must be reached throughout the tube before starting the laser to prevent condensation and thermal stress.

I solve this issue with an affordable 100W aquarium heater*. It sits in the water tank of my CW-5200 chiller* and keeps the water at a steady 20°C. The heater automatically regulates itself to avoid exceeding the set temperature. In winter, my chiller’s pump runs 24/7 to ensure warm water circulates through the tube, allowing me to laser at any time.

A CO₂ laser must be properly cooled to ensure the longevity of the tube. If the tube overheats, it will quickly fail and need replacement. While using a water bucket and pump can work temporarily, it’s not a sustainable solution.

For most situations, distilled water provides sufficient protection against freezing temperatures. For cold workshops, an inexpensive aquarium heater ensures the cooling system stays at the optimal temperature. By following these recommendations, you can keep your laser safe and functional throughout winter without risking damage.

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