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Basic Concerns with Ultrasonic Cleaning | Part 3: Cleaning Fluid

Ultrasonic cleaning is a versatile method for precision cleaning a broad range of objects. While it involves a simple process, there are several factors to consider for ensuring the best results. In this series of blogs, we’re examining seven key factors that can impact ultrasonic cleaning. 

In this article, we look at cleaning fluid (also known as detergent, soap, or cleaning solution) and discuss the part it plays in the ultrasonic cleaning process. 


Aqueous Cleaning

Why Use an Ultrasonic Cleaning Fluid

To understand why you need to use a cleaning fluid in an ultrasonic cleaner, it’s helpful to know about the chemical processes involved. 

Ultrasonic cleaners create sound waves that move through a liquid causing microscopic bubbles to form and burst in a process called cavitation. As the bubbles burst, high-speed jets of liquid hit a target object, removing contaminants from the surface of the object.  

A detergent is a surfactant, which means it lowers the surface tension of water when it’s mixed with it. Detergent molecules contain both hydrophilic (water-loving) and hydrophobic (water-hating) parts. When a detergent is added to water, contaminants – like oil or grease – are attracted to the hydrophobic parts of the cleaning solution, making them easier to remove. 

Using dish soap with a brush or cloth speeds up the process of cleaning dishes. In the same way, using a specially designed detergent in an ultrasonic cleaner makes the cleaning process quicker and more effective. The detergent loosens the contaminants on items to be cleaned and enables the ultrasonic system to increase the cavitation forces. 

Sonic Power Degreaser

Sonic Power Degreaser


Sonic Power Degreaser HD

Sonic Power Degreaser HD

Ultrasonic Cleaning Solutions & Detergents

Ultrasonic Cleaning Solutions & Detergents

Choosing the Right Ultrasonic Cleaning Fluid

Alkaline Detergents 

With a pH between 10 and 12.5, moderate to high alkalinity detergents can be used to remove a wide variety of contaminants from many types of materials. For example:  

  • Materials: ferrous and non-ferrous metals, glass, plastics, ceramics, painted surfaces, and composites 
  • Contaminants: grease, carbon, coolants, dirt, oils, cutting fluids, lubricants, buffing compounds 

Highly caustic solutions with a pH of 14 can be used if more aggressive cleaning is required, for example, to remove rust or strongly adhered contaminants. These solutions aren’t suitable for metals such as magnesium and aluminum but can usually be used on steel, stainless steel, and cast iron.  

Acidic Detergents 

Acidic cleaning fluids have a low pH and contain phosphoric acid. They are used for applications such as polishing instruments, cleaning electronic parts, and removing oxides or mineral deposits such as limescale. 

Great care must be taken with acidic cleaning solutions as they can damage the items being cleaned and even the ultrasonic cleaner itself. Some solutions contain inhibitors to prevent damage to materials such as brass, copper, and aluminum. Specially designed solutions can also be used on stainless steel, bronze, plastics, glass, and ceramics. 

Enzymatic Solutions

Enzymes are catalysts that break down organic materials such as blood and starches. Solutions containing enzymes are often used in the pharmaceutical and food industries to remove organic contaminants from objects.  

Amylase enzymes are used on starches and carbohydrates. Proteolytic enzymes help remove salvia, blood, and other proteins. 

Deionized Water

Most ultrasonic cleaning applications require some type of cleaning fluid for maximum efficacy. However, in some cases – such as with delicate materials or very light soiling – it’s acceptable or even advisable to use deionized water.  

Using the Ultrasonic Cleaning Fluid 

When you’ve selected the right cleaning fluid for your application, you need to follow the product guidelines to get the best results from your ultrasonic cleaning process. 

Cleaning Fluid Concentration 

Cleaning fluids often need to be diluted and mixed thoroughly for maximum effect and to prevent damage to the items being cleaned.  

Operating Temperature 

Operating at the right temperature for your chosen cleaning fluid is the factor with the biggest impact on the cleaning process. For alkaline cleaning solutions, a temperature of 140°F is optimum for the chemical process. Some fluids with a higher pH require higher temperatures. 

Cleaning Time 

Cleaning times vary depending on several factors, including the type of object, levels of contamination, and strength of the cleaning solution. Some objects may need a pre-cleaning cycle for maximum effect. 

Soaking, Rinsing and Drying 

Soaking isn’t required for most ultrasonic cleaning applications, but objects with strongly adhering contaminants may benefit from a pre-soak before the cleaning cycle starts. 

Most objects need to be rinsed following ultrasonic cleaning with a detergent or cleaning fluid, with immersion or spray rinsing (or both).  

Some materials need to be dried as soon as cleaning is complete to prevent oxidation.  


 Most ultrasonic cleaning solutions are caustic or acidic and could cause harm to workers and damage to some materials. It’s important to adhere to all instructions, such as wearing protective equipment, working in well-ventilated areas, and diluting cleaning fluids before use. 

Wrapping Up

Temperature is a critical factor to consider when using ultrasonic cleaning, as it can significantly impact the effectiveness and safety of the cleaning process. When determining the ideal cleaning temperature, it is important to take into account the type of cleaning solution being used, the materials being cleaned, and the level of contamination on the surfaces being cleaned. 

Do you need help designing your ideal ultrasonic cleaning application? Get in touch today! And remember to look for our next post, which will discuss how chemistry impacts the ultrasonic cleaning process. 

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