Ultrasonic cleaners are widely recognized for their ability to deep-clean a wide variety of items using high-frequency sound waves. These machines are highly effective in industries ranging from medical and dental to automotive, electronics, and jewelry. By generating millions of microscopic cavitation bubbles, ultrasonic cleaners remove dirt, oil, and grime—even from the most intricate surfaces and hard-to-reach areas.
However, not all items are suitable for ultrasonic cleaning. Some materials or components may become damaged during the process, while others pose a risk to the machine itself. To protect both your equipment and your items, it’s important to understand what should not be placed in an ultrasonic cleaner.
How Ultrasonic Cleaners Work
Ultrasonic cleaners operate using a process known as cavitation, which is the foundation of their deep-cleaning capability. These machines generate high-frequency sound waves—typically ranging from 20 kHz to 80 kHz—which are transmitted through a cleaning solution inside a tank. The sound waves travel through the liquid in rapid compression and expansion cycles, creating microscopic vacuum bubbles in the process.
These bubbles grow during the low-pressure phase and then collapse violently during the high-pressure phase. This collapse—known as cavitation implosion—releases a burst of energy and generates localized temperatures of up to 5,000 K and pressures exceeding 1000 atmospheres, though on a micro scale. While this may sound extreme, it is entirely safe for compatible objects and extremely effective at dislodging contaminants, oils, dust, oxidation, polishing compounds, and even bacteria.
The cleaning action is non-contact, meaning it does not rely on physical scrubbing. Instead, millions of these microscopic implosions occur every second, reaching into crevices, blind holes, fine engravings, and intricate surfaces that traditional cleaning methods cannot access.
Some ultrasonic cleaners are equipped with features such as:
- Degassing functions: to remove trapped air from the cleaning solution, improving cavitation efficiency
- Sweep frequency modes: which vary the ultrasonic frequency slightly to ensure even cleaning and reduce standing waves
- Heating elements: which warm the solution to improve detergent activity and reduce cleaning time
- Digital timers and programmable cycles: allowing precise control over cleaning duration, ensuring delicate items are not overexposed while supporting repeatable, automated cleaning processes.
Because cavitation is uniform throughout the liquid medium, the cleaning is evenly distributed, ensuring consistent results across all surfaces—visible and hidden. This makes ultrasonic cleaners ideal for cleaning delicate, intricate, or sensitive items in industries such as medical, jewelry, automotive, aerospace, and electronics.
Items You Should Never Put in an Ultrasonic Cleaner
Here are common categories of items that are not suitable for ultrasonic cleaning, along with the reasons why:
1. Items with Non-Removable Seals or Watertight Casings
- Examples: Watches, sealed sensors, certain fitness trackers
- Why: Ultrasonic vibrations can compromise gaskets and seals, allowing moisture to seep into sensitive components. Once seals are damaged, the item may lose its water resistance permanently.
2. Rubber and Soft Plastics
- Examples: Rubber gaskets, silicone ear tips, flexible seals
- Why: The combination of heat and vibration can cause soft materials to degrade, swell, or crack over time, especially with repeated exposure.
3. Wood and Porous Materials
- Examples: Wooden handles, inlays, natural cork, leather
- Why: Porous materials absorb water, and ultrasonic agitation can cause warping, splitting, or discoloration. Wood can also deteriorate when subjected to prolonged immersion.
4. Items with Embedded or Exposed Electronics
- Examples: Smartphones, computer parts, hearing aids, remote controls
- Why: Ultrasonic cleaning can damage circuit boards, microchips, and solder joints. The process also introduces moisture, which can lead to short-circuiting or corrosion.
5. Flammable or Combustible Materials
- Examples: Lighters, aerosol containers, objects soaked in fuel or alcohol
- Why: Flammable substances pose a serious fire or explosion hazard when exposed to heat and vibration. Ultrasonic cleaners should never be used with volatile liquids or items that retain them.
6. Jewelry with Fragile or Porous Gemstones
While ultrasonic cleaners are commonly used to clean jewelry, some stones are too delicate for this method. Avoid cleaning jewelry that contains the following materials:
- Soft or porous gemstones:
- Pearl, Amber, Opal, Turquoise, Malachite, Lapis Lazuli, Mother of Pearl, Feldspar, Onyx
- Heat-sensitive or fracture-prone stones:
- Topaz, Emerald, some colored diamonds
- Brittle metals:
- Tungsten (can crack under vibration)
Why: These stones may be porous, fracture-prone, heat-sensitive, or treated with dyes or coatings that can degrade in an ultrasonic environment. Vibration may also loosen settings or adhesives used in certain types of jewelry.
7. Items with Loose or Delicate Components
- Examples: Antique items, costume jewelry, items with glued parts
- Why: Cavitation can cause small parts to come loose or adhesives to dissolve, leading to damage or detachment. In antiques, fragile metalwork or aged materials may not withstand vibration.
Best Practices to Avoid Damage
- Check manufacturer guidelines: Always refer to care instructions before cleaning an item ultrasonically.
- Perform a spot test: When in doubt, test a small non-visible area or clean manually instead.
- Avoid overloading the tank with items; it reduces effectiveness and increases the risk of damage.
- Use the right frequency: Higher frequencies (e.g., 68–80 kHz) are gentler, while lower ones (20–28 kHz) are more aggressive.
- Use proper cleaning solutions: Never use flammable or corrosive chemicals in an ultrasonic cleaner.
Final Considerations
Ultrasonic cleaners are incredibly useful tools—but like all high-performance machines, they require thoughtful use. Understanding which materials and components are unsuitable for ultrasonic cleaning is essential to protect your items and preserve the longevity of your cleaner. When in doubt, consult with the manufacturer or a cleaning specialist to determine the safest method for your specific application.
By using ultrasonic cleaning selectively and responsibly, you’ll continue to enjoy its powerful benefits without risking costly damage.
Granbo is a high-tech enterprise specializing in ultrasonic technology, integrating R&D, innovation, manufacturing, sales, and technical support. With a strong foundation in advanced engineering and a commitment to quality, Granbo offers a wide range of ultrasonic cleaning solutions that are trusted across biomedical laboratories, manufacturing workshops, food processing facilities, electronics, and commercial sectors. Whether precision, power control, frequency flexibility, or quiet operation is the priority, Granbo’s equipment is thoughtfully designed to meet the challenges of modern cleaning tasks.
If you would like to learn more or are considering a suitable ultrasonic cleaning solution for your needs, feel free to reach out for further consultation, we’re here to assist with any questions or technical support!
