Degassing is the process of removing dissolved air from the liquid inside an ultrasonic cleaner before you start cleaning parts. Fresh water or cleaning solution holds tiny air bubbles that interfere with the cleaning action, so running a degas cycle first ensures the machine works at full power. Most ultrasonic cleaners either have a dedicated degas button or allow you to degas by simply running the unit empty for 5 to 10 minutes.
Why Dissolved Air Weakens Cleaning Power
Ultrasonic cleaners work by creating millions of microscopic cavitation bubbles in the liquid. These bubbles form, grow, and then violently collapse against the surface of whatever you’re cleaning, blasting away contaminants with tiny jets of liquid and shock waves. That collapse is where all the cleaning energy comes from.
When dissolved air is still present in the solution, it gets trapped inside those cavitation bubbles. Air-filled bubbles behave very differently from the vapor-filled bubbles you actually want. Instead of collapsing rapidly and violently, gas-filled bubbles act like tiny cushions. They compress and bounce back gently rather than imploding, producing far less cleaning force. Researchers describe this as the “gas cushion effect,” and it’s the reason a freshly filled ultrasonic tank cleans noticeably worse than one that’s been properly degassed. You may hear a rougher, uneven sound from the tank when air is still present, which smooths out once degassing is complete.
How a Degas Cycle Works
A degas cycle uses the ultrasonic transducers themselves, but in a pulsed pattern rather than continuous operation. The unit switches on and off in repeating cycles, typically with a duty cycle between 10% and 50%. That means it might run ultrasonic energy for a fraction of a second, pause, then fire again. This pulsing agitates the liquid enough to shake dissolved gas out of solution and push it to the surface, where it escapes into the air above the tank.
Some machines label this a “degas” button. Others simply use a “pulse” or “sweep” mode that serves the same purpose. On units without a dedicated mode, you can achieve the same result by running the cleaner normally with no parts inside the tank.
How Long Degassing Takes
The time depends on tank size and liquid temperature. For a small benchtop unit with heated solution, running the ultrasonics without parts typically takes 5 to 10 minutes. Larger tanks can take significantly longer, sometimes 30 minutes to an hour or more. An unheated tank may need several hours to fully degas because cold liquid holds onto dissolved gas more stubbornly than warm liquid does.
Heating the solution speeds things up considerably. Warmer liquids have lower gas solubility, meaning air naturally wants to escape as the temperature rises. Running ultrasonic energy and heat together is the fastest approach. If you’re in no rush, you can also just let the filled tank sit uncovered for several hours and the air will gradually release on its own, though this is the slowest method by far.
The good news is that once a batch of solution is degassed, it stays degassed. You only need to repeat the process when you dump the tank and refill with fresh liquid.
When Degassing Matters Most
Degassing matters any time you want consistent, thorough cleaning, but it’s especially important in certain fields. Medical and surgical instrument reprocessing guidelines from organizations like AORN specifically instruct sterile processing departments to follow the ultrasonic cleaner manufacturer’s instructions for degassing before processing instruments. The logic is straightforward: if trapped air reduces cavitation intensity, instruments may not be fully cleaned, and incomplete cleaning undermines the entire sterilization chain.
The same principle applies in jewelry cleaning, electronics manufacturing, firearms maintenance, and laboratory work. Any application where you’re relying on the ultrasonic cleaner to remove fine particulate, oils, or biological material will benefit from proper degassing. Skipping it doesn’t break anything, but it means you’re running the machine below its potential, which can lead to inconsistent results or the need for longer cleaning cycles.
Practical Tips for Effective Degassing
- Add your cleaning solution first. Degassing should happen after you’ve mixed in any detergent or cleaning concentrate, since adding chemicals to already-degassed water reintroduces air.
- Use heat if your unit has it. Setting the heater to the recommended cleaning temperature before or during degassing cuts the time significantly compared to running at room temperature.
- Listen to the tank. During degassing, you’ll often hear a louder, higher-pitched, or more erratic sound. As dissolved air clears, the tone becomes smoother and more uniform. That audible shift is a reliable cue that degassing is nearly complete.
- Don’t load parts early. Putting items in the tank during the degas cycle means they’re being “cleaned” with reduced cavitation energy. Wait until degassing finishes, then load your parts for the actual cleaning cycle.