Frequently Asked Questions about Ultrasonic Cleaners

If you’re thinking about purchasing an ultrasonic cleaner for the first time, you probably have some questions about the technology and best practices for use. The following is a list of commonly asked questions followed by their answers:

Do ultrasonic cleaners really work?

Yes, ultrasonic cleaners really work when properly specified and operated using ultrasonic cleaning solutions formulated for specific cleaning tasks. Ultrasonic cleaners really work when cleaning hard materials such as metals, plastics, glass and ceramics or other products that can be safely immersed in a liquid.  They also really work on parts with complex shapes such as cracks, crevices and blind holes difficult to access by other cleaning methods.

Examples of Where Ultrasonic Cleaners Work

• Volkswagen Group America and Canada dealers use an ultrasonic cleaner system for fuel injector cleaning. Parts reach the necessary degree of cleanliness in a short time with no manual finishing or touching up and no damage to the parts being cleaned.
• Online discussion forums bat around the best solutions to clean gasoline engine carburetors.  The complex mechanisms previously required almost total disassembly, time-consuming cleaning then reassembly.  Ultrasonic cleaners are fast. Cleaning can be accomplished in as little as 20 minutes with minimal disassembly.
• Ultrasonic cleaning is the preferred method of removing toughly adhering contaminants from complex shapes, precision finishes and vents characteristic of costly plastic injection molds.
• Ultrasonic passivation for stainless steel meets ASTM A967 standards to remove free iron and other contaminants from AISI Types 304, 310 and 316 stainless steels used in food, chemical and pharmaceutical processing, surgical implants, architecture and transportation.
• Applications for 3D printing have moved far beyond the curiosity stage to a widely accepted means of fabricating products.  The efficiencies of 3D printing are greatly enhanced by employing ultrasonic cleaners to remove 3D mold support.
• Diesel particulate and exhaust gas recirculation cooler filters become clogged and inefficient over time. An ultrasonic cleaner far outperforms compressed air, fuel tank additives, aerosols, hot-water sprays and similar DPF and EGR maintenance techniques.
• Cleaning jet engine fuel nozzle manifold adapter assemblies must be accomplished after specified hours of operation.  An ultrasonic cleaner is faster, safer and less damaging than mechanical methods to remove baked on carbon deposits from precisely fabricated, highly machined fuel nozzle surfaces.
• For law enforcement agencies, hunting clubs, shooting clubs and collectors, an ultrasonic gun cleaning and lubricating system is a real time saver that delivers results far superior to using brushes, sprays and solvents. 
• Restoration services and hobbyists make use of ultrasonic energy to clean and restore vintage hardware by removing tarnish and layers of paint. The restoration process is made faster and easier when using an ultrasonic cleaning solution formulated to attack paint or tarnishes being removed.

Examples of Ultrasonic Cleaner Use in Labs

University and corporate research labs make broad use of ultrasonic cleaners to support research and maintenance activities.

• For example, sample preparation in a sonicator bath is used to extract an active pharmaceutical ingredient (API) from its carrier, or excipient, prior to conducting content uniformity and potency assay tests. Many USP monographs recommend using an ultrasonic bath to dissolve samples prior to analysis.
• In Quality Control operations ultrasonic cleaners support standardized, repetitive procedures to improve efficiency and reproducibility.  In R&D applications ultrasonic cleaners such as the Elmasonic Select Series with time-saving programmable cleaning cycles support standardized operations.
• Laboratory equipment cleaning can involve complex configurations difficult to clean manually, and also pose danger to personnel due to breakage.  That’s why labs employ an ultrasonic cleaner for cleaning delicate glassware, pipettes, and complex instruments safely and efficiently.
• Manifold tube clogs are the most common source of failure on plate washers used in biopharm labs using microplates for assays and ELISA applications.  A benchtop ultrasonic cleaner proved superior an automated unit for cleaning clogged microtubes.

How do I select my ultrasonic cleaner?

If you are cleaning parts, to get started you need to consider the following before making a selection: (Scroll down for information on sample prep in the lab.)

• Type of contamination to be removed.  There’s a big difference, as you can imagine, between removing coolant from machined parts, varnish deposits from a carburetor, ink from printing rolls, and blood and tissue residues from surgical instruments.
• The composition of products being cleaned.  Different parameters apply to cleaning aircraft engine components and glass capillaries. You’ll need compatible cleaning solution and ultrasonic cleaning frequency.
• How will the parts be used after cleaning? 
• How do you define ‘clean’?
• Will you be cleaning batches or individual parts?
•  Component size and weight

Once you define exactly what you’re trying to accomplish the following points will help narrow down your equipment selection. Then it’s time to contact the scientists at iUltrasonic for specific recommendations.

What is the difference between a cheap and an expensive ultrasonic cleaner?

A quick web search shows ultrasonic cleaners are available in a broad range of price points.  As with most any purchase of a technical nature, you get what you pay for.

Putting it another way, if an ultrasonic cleaner is essential to the success of your business or hobby, chances are that purchasing a cheap unit will soon lead to disappointment. Among disappointments you may experience after buying a cheap ultrasonic cleaner are included:

• Inability to “do the jobs” you assign to it
• Overheating soon into cleaning cycles
• Noisy operation due to “cheap” construction, and
• Lack of servicing if your unit malfunctions

Consider Construction, Operating Features & Requirements

If you need a unit that offers more than a simple on-off switch, here are some spec points to consider:

• Stainless steel cleaning tanks (welded if you run long-term cycles) with a 2- or 3-year warranty
• Standard/selectable operating features that simplify cleaning or sample-prep tasks. Examples include
  • Sweep for uniform cleaning
  • Pulse for added power to remove stubborn contaminants
  • Dynamic, combining sweep and pulse for optimized performance
  • Degas to remove trapped air from fresh cleaning solutions
  • Eco for quieter, gentle cleaning
  • Thermostats to heat cleaning solutions to the recommended temperature
  • Programmable cycles for repetitive tasks boost plant efficiency
  • Adjustable power to tailor operations to specific tasks
  • Selectable ultrasonic frequencies (such as 37/80 or 25/45 kHz)
• Specific requirements. For example, ultrasonic cleaning systems are available for laboratory instruments, gun cleaning systems, carburetor cleaning  and as sonicator baths.

Key Takeaway on Cheap vs. Expensive Ultrasonic Cleaners

Carefully consider why you are purchasing an ultrasonic cleaner, and how much its performance impacts the success of your application(s).  If in doubt, contact the experts at iUltrasonic for unbiased advice.

How to select the proper size of an ultrasonic cleaner?

Measure the dimensions of largest parts to be cleaned and make sure to select a tank that will accommodate these parts.  In addition, pay attention to the internal dimensions of the parts basket, since this is most likely where you will put the parts during cleaning. Questions about baskets are covered next.

You’ll also need to know the working depth of the cleaning fluid as it relates to the size of parts you’re cleaning. The working depth is the distance from the bottom of the basket to the surface of the liquid in a filled tank. It’s important because parts being cleaned must be fully immersed in the liquid.

Product specs for benchtop ultrasonic cleaners may not include this information. If they do not, feel free to contact the manufacturer or the scientists at iUltrasonic for this information. 

Do you have to use a basket in an ultrasonic cleaner?

Yes. Items being cleaned must NOT contact the ultrasonic cleaner tank. If they do serious damage to tanks occur – eventually causing penetration rendering your equipment investment worthless.

Cleaning baskets are designed to fit within the cleaning tank and hold products at the optimum distance from the tank bottom to ensure maximum cavitation efficiency during the cleaning process.  

Note: Cleaning basket dimensions are less than tank internal dimensions. This is important to keep in mind when specifying an ultrasonic cleaner.

Modular cleaning basket designs can incorporate partitions, multiple levels, part supports, and other features allowing unlimited flexibility in parts positioning. 

Professional Tip: To avoid damage to parts and those with high finishes, items being cleaned should not contact each other. Don’t crowd them in the basket, instead schedule separate cleaning cycles. 

Exceptions to using baskets:

Baskets may be impractical when cleaning very large parts in an industrial ultrasonic cleaner.  In such cases, parts can either be suspended in the cleaning solution from overhead cranes or rest on ridges fabricated onto the bottom of the cleaning tank.

When cleaning items such as jewelry, you can suspend the pieces into the cleaning solution from supporting hook racks resting on the tank rim.

Beaker-supporting lids in several sizes are available to suspend beakers filled with small parts and the cleaning solution at the proper level in the ultrasonic cleaner tank.  Small parts can be placed in fine mesh baskets for easy handling.

Do the ultrasonic cleaner need a heater? 

Most cleaning operations are much more effective with heating. A heated cleaning solution is best for removing oils, machining coolants and a whole host of other contaminants from just about any surface you can think of. 

Although heat is a natural byproduct of ultrasonic cavitation, cleaning efficiency increases when you give it a boost by using ultrasonic cleaners with thermostat-controlled heaters. These can be adjusted in increments to 80⁰C above which cavitation is inhibited and cleaning efficiency levels off.

On the other hand if you are removing blood, don’t use heat at all.

What is a sweep mode? 

Sweep mode is a small continuous variation of the ultrasonic frequency around a central value, such as 40 kHz ±3 kHz.

When an ultrasonic cleaner operates at a fixed frequency without Sweep there are three potential problems: ‘hot spots’, ‘dead zones’, and harmonic vibrations. 

Hot spots are areas with a high concentration of cavitation bubbles, i.e. a stronger ultrasonic effect. If the ultrasonic cleaning is too intense this can cause etching on delicate parts with fine features, on polished surfaces, on soft metals, or on thin metal layers. 

Dead zones are areas where there is no cavitation, i.e. no cleaning. 

Harmonic vibration can develop when the fixed ultrasonic frequency causes parts to resonate. This is potentially damaging to sensitive components such as fine wires or crystals.  Harmonic vibration is particularly undesirable when cleaning electronics and printed circuit boards. Always choose an ultrasonic cleaner with Sweep mode for electronics cleaning.

Select a unit with a Sweep mode if you are cleaning precision parts and surgical instruments where highly uniform cleaning is needed.  It is less important when the results need not be perfect, such as degreasing carburetors and fuel injectors. 

How to I select an ultrasonic frequency? 

Most ultrasonic cleaners operate between 35 and 45 kHz. This frequency range is well suited to the vast majority of cleaning tasks. 

A lower frequency such as 25 kHz produces larger cavitation bubbles. When these bubbles implode they release a stronger cleaning energy.  For coarse cleaning such as removal of lapping abrasives or polishing paste, a lower frequency will be more effective. 

Note that the lower the frequency, the louder the cleaning operation due to tank wall vibrations. Lids (which also reduce evaporation), sound-deadening enclosures and ear protection are ways to reduce annoying ultrasonic noise.    

A higher frequency produces smaller cavitation bubbles.  These cover fine featured complex surfaces more thoroughly and are gentler than low frequencies. For fine cleaning of very delicate jewelry, electronics, and soft metals with polished surfaces consider a unit operating at 80 - 130 kHz.  If you are cleaning capillary tubes or spectrophotometer cuvettes you will need a unit that operates at 80 kHz or higher.

If you are cleaning a variety of materials consider dual-frequency ultrasonic cleaners available from iUltrasonic. 

What is important about degas and pulse modes? 

Every time you fill the tank with fresh cleaning solution you must degas the solution before the unit can clean effectively. Entrained or dissolved air inhibits cavitation, and cavitation is the mechanism that accomplishes the cleaning. A Degas mode will enable you start cleaning sooner after you fill the tank. It does the job by switching on and off causing air bubbles to coalesce and allowing them rise to the surface and burst.

Pulse mode provides intermittent spikes of very high ultrasonic power to remove stubborn contaminants.  Pulse mode also degasses solutions very effectively.

If you are degassing solvents select a model that has either a Degas mode or a Pulse mode. An ultrasonic cleaner without these modes will also degas your solvents, but will do so at a slower rate.  (See below on preparing lab samples.)

What is important about ultrasonic power? 

 ‘When talking about power which model is stronger?’ sounds like a simple question but it’s not.

Some manufacturers report ultrasonic peak power, others report average power, and some report both. When an ultrasonic cleaner is running electrical power is consumed evenly but it is released in intervals to create sound waves. These intervals produce the wave shape of the ultrasonic signal. 

Rather than put you to sleep with more on this topic, the important thing to keep in mind that while more power usually indicates faster and more effective cleaning, more power is not always better. Too much power can damage electronic parts, the surface finish on a soft metal (e.g. aluminum), and other delicate items. For cleaning extremely sensitive items, adjustable power is a useful feature.  

And a caution: Don’t try to increase the effective power of an ultrasonic cleaner by under-filling the tank.  Ultrasonic cleaner generators that power transducers are tuned to a particular fill level. Operating the unit with less fluid can damage the generator and will result in less than optimized cleaning.

What do I need for preparing lab samples?

Purchase a unit that has both Sweep and Normal (fixed frequency) modes. Trial and error will indicate which mode will best dissolve, disperse, homogenize, or mix your samples.  

If you are disaggregating liposomes, select a unit with adjustable power since you will need to find the power level that disperses your samples without damaging them. If you are dispersing nanoparticles, select a unit with extremely high ultrasonic power. 

Similarly, if you are working with difficult to dissolve samples, select a high power unit. Pulse mode, which produces intermittent power spikes, will also assist in dissolving challenging samples. 

A variety of accessories are available to support the use of ultrasonic cleaners in the lab. Blending, dissolving and dispersing are facilitated when suspending samples in a water bath with a surfactant. Use Erlenmeyer flask holders, flask clamps, test tube holders or specially designed lids to hold beakers. If high bath temperatures are a concern a cooling coil attached to a cold water line serves as a heat exchanger to prevent the bath from heating up.

What liquid should I put in an ultrasonic cleaner?

Soaps, chemicals, cleaning solutions and cleaning formulas describe the “liquids” professionals put in their ultrasonic cleaner to solve specific cleaning challenges. Water from the kitchen tap will almost always yield unsatisfactory results.

Today, most ultrasonic cleaning liquids are offered in the form of biodegradable concentrates.  This reduces or eliminates the disposal concerns of earlier formulations, and also provides the economies of dilution. In other words, a little goes a long way.

The liquid you should use in your ultrasonic cleaner requires an understanding of the products being cleaned and the nature of the contaminants.

Contrary to what you may see offered online, including recipes for kitchen concoctions, there seldom is a one-size-fits-all answer to “what liquid should I put in an ultrasonic cleaner?”

So, if you are serious about getting the best results from your ultrasonic cleaning operations, you’ll pay particular attention to the types of ultrasonic cleaning solutions available.

For detailed information, the scientists at iUltrasonic strongly suggest you read our ultrasonic cleaning solution selection tips. 

It describes in easy-to-understand language types of cleaning solution formulas, where they find application and how to maximize their effectiveness over multiple cleaning cycles.

Can you use tap water in an ultrasonic cleaner?

Yes, you should use tap water to dilute the cleaning concentrate. Using tap water alone without any additional chemicals or soap will significantly reduce the cleaning effectiveness. It would be like washing dishes without dish soap.  If you want the parts to dry completely spot-free, you should rinse them with distilled or deionized water after washing. 

Can you use water and dish soap in an ultrasonic cleaner?

Yes, you can wash parts with water and dish soap in an ultrasonic cleaner, but you will get faster and more thorough results with a cleaning solution formulated for ultrasonic cleaning. Avoid any solutions that foam.  Ultrasonic cleaning solutions are always formulated to be non-foaming.

What is a good ultrasonic cleaning solution?

If you’re planning to clean lots of different types of items and want to choose one solution that will work for all of them, Elma tec clean A4 universal ultrasonic cleaning concentrate is an excellent choice.  Elma tec clean A4 will remove oil, grease, combustion residue, soot, organic contamination, dust, and fingerprints from surfaces made of metal, glass, plastic, ceramics, and rubber.  Dilute this solution to 1-5% with water before use.

Can you put isopropyl alcohol in an ultrasonic cleaner?

It is an explosion hazard to fill your ultrasonic cleaner with a flammable solvent such as isopropyl alcohol (IPA). Although you should never put IPA directly in the tank, you can mitigate the risk by using a secondary container.  You can partially fill the tank with water and a bit of detergent, then position a glass beaker containing IPA in the water.  The ultrasonic cleaning power will pass through the walls of the beaker into the IPA. Items to be cleaned should be placed inside the beaker which should be covered to minimize evaporation.  The entire set-up should be inside a fume hood or other extremely well-ventilated location where the solvent vapor cannot accumulate.

What can be cleaned with an ultrasonic cleaner?

An ultrasonic cleaner can be used to clean most items that can safely be submerged in water. Cleaning is most effective on hard surfaces made of metal, glass, or plastic. Popular uses for ultrasonic cleaners include cleaning of carburetors, printed circuit boards, medical and dental instruments, jewelry, watch parts, machined metal parts, firearms, paint gun nozzles, fuel injectors, plastic injection molds, and 3D printed parts. Ultrasonic cleaners are used to clean newly manufactured items and to maintain equipment.

What should you never put in an ultrasonic cleaner?

Let’s start with something very important:

Never put your hand into an operating ultrasonic cleaner!

Ultrasonic cleaners use the power of cavitation to loosen and carry away contaminants from products being cleaned.  The process is described in How do Ultrasonic Cleaners Work?

Cavitation action can pass through plastic and glass to work in products suspended in special cleaning formulations.  This means it can pass through your skin or gloved hands if you immerse them in an operating bath, and act on blood and tissues. This is NOT GOOD.

Operating an ultrasonic bath also increases the temperature of the cleaning solution whether or not you employ the unit’s heater. This can cause burns when removing items after a cleaning cycle.  Wear gloves or allow parts to cool before handing.

Products damaged by ultrasonic cleaning

While ultrasonic cleaners are widely used in jewelry manufacturing and restoration, fragile or soft stones such as pearls, opals, emeralds and amber should not be cleaned with ultrasonics.

Highly polished surfaces of relatively soft metals such as aluminum can be damaged in an ultrasonic cleaner unless operators utilize high frequencies and control the ultrasonic power. 

In these cases units such as the Elmasonic P series of cleaners, featuring dual frequency and adjustable power, can be employed.

What are the hazards of an ultrasonic cleaner?

Serious problems can and do occur when flammable solvents such as readily available acetone and IPA are used in an ultrasonic cleaner.  These volatile solvents release vapors that are ignited by any external ignition source, and create what the NFPA classifies as a hazardous area.

Such solvents are widely used when an ultrasonic cleaner is employed for specialized cleaning tasks as well as performing certain sample preparation exercises in laboratories.

Options available when cleaning with flammable solvents include benchtop solvent cleaning kits for small parts cleaning or sample preparation, or explosion proof ultrasonic cleaners for larger parts cleaning.

Cleaning with IPA, toluene, acetone or other low-flash-point solvents presents some very serious safety issues.  If your operation calls for such cleaning we invite you to check our best practices for cleaning with flammable solvents

Noise can present a hazard when operating ultrasonic cleaners, especially at lower frequencies.  This can commonly occur when industrial units operate on long-term cleaning cycles.

For operator comfort and safety, two remedies can be considered.  The first is providing industrial noise hearing protection or safety ear muffs to employees.

The other, which allows normal conversations to occur in the cleaning area, is to place benchtop ultrasonic cleaners in mute boxes that can reduce sound by up to 85%.

Large industrial ultrasonic cleaners can be equipped with noise-reduction lids that also reduce cleaning solution evaporation.

Other potential hazards can occur in any industrial setting and not confined to ultrasonic cleaning.  These include policing areas for spilled water, faulty electrical components and encouraging employees to keep their minds and eyes on the job and not their smartphones.

Find out more on why ultrasonic cleaners really work

Contact the ultrasonic cleaning experts at iUltrasonic. We are ready to answer your questions and recommend the best ultrasonic cleaner, cleaning solution formula(s) and procedures to meet your stringent requirements.