Analytical instrumentation
Foam presents persistent challenges across industries such as food processing, chemical manufacturing, and petroleum refining, where it can disrupt operations, reduce efficiency, and damage equipment. Defoamers, which either prevent foam formation (antifoams) or eliminate existing foam, are widely employed to mitigate these issues. Silicone-based defoamers, particularly polydimethylsiloxane, dominate industrial use due to their chemical stability, temperature resistance, and long service life, albeit non-silicone alternatives remain important for biodegradable or cost-effective applications.
The effectiveness of a defoamer depends on several factors such as droplet size, surface tension, temperature, and bubble formation rate, all of which must be optimized for specific systems. Evaluation methods range from simple manual tests to advanced instrumentation like Koehler Instrument Company’s D892 and D6082 Dual Twin Foaming Characteristics Test Apparatus, which enables precise control of fluid conditions for reproducible results.
Overall, defoamers remain an essential solution for foam management, ensuring process reliability while enhancing industrial safety and efficiency. This paper will discuss impacts of foam on industries specifically on lubrication as well as the uses of defoamers to mitigate problems that arise. Various methods and equipment used to evaluate foam’s characteristics are also discussed.
Foam are the bubbles produced from the dispersion of gas. The creation of foam can be caused by physical or chemical properties; variables such as temperature, pressures, and additives can affect the foam produced [1]. While some industries use foam as a tool, others consider it to be a major obstacle. Industries such as natural gas, petroleum refining, and food production can be negatively impacted by foam formations, including equipment degradation, unstable heat dissipation, and safety hazards [2].
Ultimately, creating an inefficient production system [3]. While each of these mentioned industries are affected by foam in their own ways, foaming in lubricants tends to be of utmost concern for them all [1].
Lubricants play a vital and ubiquitous role across many industries, but they face challenges caused by foam. A lubricant serves to reduce friction between moving parts and ultimately extend the lifecycle of equipment [1]. However, the presence of foam can reduce lubricating fluidity which can lead to problems such as improper heat dissipation and inadequate oil cooling. [1]
Moreover, the combination of high working temperatures and foam can increase oxidization, resulting in a sludge that can limit the lubricant oil’s capabilities and cause dry friction as well as damage to machinery parts [4]. Pure lubricant oil doesn’t tend to foam, however, there are an assortment of variables that can influence foam production [1].
Factors such as a system’s aeration rate, temperature, and pressure can affect foam formation while the composition of the oil can greatly influence a foam’s formational stability [1]. Oil has about 10% volume at room temperature and atmospheric pressure which will be considered dissolved air. However, once pressure starts to fluctuate air bubbles can become visible and referred to as entrained air. For lubricants such as mineral oil, when the volume of entrained air reaches 30% foam can form [5]. Figure 1 shows different ways air can be dispersed in oil [5].
Surfactants can be incorporated into oil for enhancements such as anticorrosive and cleansing purposes [1]. Surfactants are composed of hydrophobic and hydrophilic components [1]. Some surfactants used in lubricants can be detergents such as sulfates, or rust inhibitors like metal phenolates [6]. As shown in Figure 2, when foam is formed, the hydrophilic component will be pointing out towards the liquid and the hydrophobic component will be pointing inside the bubbles [1, 7].
This helps create and stabilize the lamella by reducing the gas-liquid interfacial tension which will encourage foam formation and resistance [1].
There are two ways to combat issues faced by foam, either prevent the creation of foam or remove the foam itself [2]. The former can be achieved through anti-foaming agents. These are added to a system before foam formation and coat the surface of a liquid, hindering any potential foam formation [2]. By comparison, in the latter case, defoamers are added after the foam is formed.
They will spread to the thin layer between the liquid and air, referred to as the lamella [3]. This can cause thinning of the lamella and break down foam bubbles until they collapse [2]. Despite their differing approaches, both methods perform the same function and are often applied in practice, typically being referred to as defoamers.
There are a variety of factors that can influence a defoamer’s capability, such as droplet size, temperature, and rate of bubble formation [3, 8]. Adjustments to these factors are unique to each defoamer and need to be studied individually for optimal results. Defoamers can be driven physically or chemically [1]. Defoaming through physical properties can include changes in temperatures or pressure that can be advantageous due to their minimal impact on the environment.
However, the conditions that must be met are limited and do not have as high defoaming rates compared to chemical defoamers [1]. Chemical defoamers apply defoaming agents to mitigate foam and its formation. Figure 3 shows the process of a defoamer when applied to a fluid [3]. When a defoamer is first incorporated, it will dissipate throughout the fluid. It will then create a thinning on the lamella, resulting in rupture [9].
A defoamer should have three basic components as shown in Table 1 [3]. The first component, referred to as the active component, is responsible for defoaming. The second component is a carrier fluid, commonly a mineral- or silicone-based oil, that will disperse the active component by lowering the viscosity and improving the overall success of the defoamer [10]. An emulsifier is the final component needed. Emulsifiers improve the stability and dispersion of the active component in the fluid [3].
The components can be sufficed with the same substance; for example, silicon can be both the active component as well as the carrier fluid [11].
Defoamers should have certain attributes to enhance efficiency, including small surface tension, chemical stability, heat resistance, oxidation resistance, and strong defoaming power. Nonetheless, these various conditions are difficult to all meet simultaneously [1]. For this reason, many defoamers are studied on a case-by-case basis.
Silicon defoamers are most effective in industrial applications, with polydimethylsiloxane (PDMS) oils being the most commonly used [1]. Referred to as dimethicone, this PDMS has a low surface tension along with a high temperature resistance [1]. Silicone is also considered to be chemically inert [13]. This allows for silicone defoamers to be easily applicable to industries such as chemical manufacturing, food processing, and petroleum refinement [9].
Additionally, the longevity of silicone defoamers allows less maintenance to be done, resulting in this method being cost effective over extended durations of time [14]. Table 2 shown below highlights key components of silicone and non-silicone defoamers.
Non-silicone defoamers are another kind of chemical defoamer. These are composed of materials including alcohols, fatty acids, and mineral oils [13]. Non-silicone defoamers are usually not as efficient as silicone-type but are still in use for their affordability and generally moderate efficiency [14]. Their biodegradability is another beneficial characteristic of these defoamers which is why they are commonly used in agricultural practices [14].
Although non-silicone defoamers lack the efficiency and versatility of silicone, their advantages may be appealing depending on the industry and purpose.
Before a defoamers is applied, studies and tests should be done to recognize its efficiency and safety. These tests can create environments that simulate the conditions a defoamer would be applied to [10]. Table 3 provides information on an assortment of common testing methods (while stirring and blender method can be used for bulk foams, the ones referenced in the table are used without complex pieces of equipment) [15].
Apparatuses such as Figure 4 have been created to provide further observations of foam [16]. Using specifically designed equipment can be beneficial to observe a foam in industry-like conditions. A study affiliated with Center for Integrative Petroleum Research at King Fahd University of Petroleum and Minerals was done by Adebayo et al. in which a comparison was made between the bulk foam and coreflood testing [15].
The same surfactant was used for both approaches and studied a foam’s characterization to determine an optimal surfactant percentage. A standard foam stabilizer was used for bulk foam testing. For the core testing, chalk and sandstone were used as porous material for the apparatus. Both tests showed an optimal concentration at a weight percent of 2.5%. For these results to be met, the filter size of the bulk tester must be the same as the porous material used in core testing [15].
A study done by Nasr et al. also compared the two testing methods [16]. Conducted at COREOR center of University Teknologi, the study took three surfactants commonly used in the oil industry (MFOMAX, AOS, and ENORDET) to be tested. Determining certain attributes varies between the two methods. For example, in core flooding, the peak foamability was based on pressure drop; in bulk foaming, it was based on the foam’s volume.
To compare the two, each set of data was normalized into a fraction. Figure 5 illustrates these results [16]. Out of the four individual parameters tested, two showed corroborations of the testing methods. However, the numbers obtained were not the same.
For example, when measuring peak foamability, MFOMAX was found to be the highest and ENORDET the lowest. However, the difference between the fraction values for ENORDET was roughly 0.4, with the core flood’s data being higher. Although all the bulk foam’s individual sets of data didn’t agree with those from core flooding, both did agree on the same overall conclusion of MFOMAX having the best performance. [16]
While coreflooding appears to be the superior option, it does have its limitations. Coreflooding machinery can be quite costly [15]. The process of obtaining the results can also be time-consuming and intensive, with results that can take days and consistent process monitoring. Fortunately, bulk foaming apparatuses can offer controlled environments and efficiency [15]. Koehler Instrument Company’s D892 and D6082 Dual Twin Foaming Characteristics Test Apparatus shown in Figure 6 is an example of this [17].
Koehler’s device is composed of two baths: one for the cooler temperature at 24° C and one for temperatures up to 150°C.
A fluid is blown into the baths at a fixed volume and controlled temperature. The foam produced is then measured at set intervals after each aeration period. The apparatus also records the amount of time for the foam levels to reach zero. This device allows a more controlled environment and can be useful for the testing of fluids that face severe conditions such as lubricating oil.
Foam is a persistent issue many industries face. For lubricant oils especially, foam can cause degradation in performance and safety risks [2]. While defoamers are a common and reliable solution to fluid foaming, they range in purpose, composition, and capabilities that complicates the ascertaining of a single optimal solution [2].
Hence, testing methods are a necessity in studying the classifications of defoamers and their conditions needed to reduce foaming. Coreflooding provides a descriptive evaluation of a foam but is extremely time-consuming and costly. Meanwhile, bulk foaming can provide somewhat similar results in a more efficient manner but does not offer intensive data collection as that of coreflooding [15].
Consequently, there is not one “right” testing method used, and the testing parameters heavily rely on proper stimulation of foaming environments as well as the specificity of results [3]. The industries that interact with foam formations are well-diverse and, as a result, must uphold their own subjective defoamer requirements and limitations with compatible evaluation methods [1].
Dr. Raj Shah is a Director at Koehler Instrument Company in New York, Holtsville, NY. He is an elected Fellow by his peers at ASTM, IChemE, CMI, STLE, AIC, NLGI, INSTMC, AOCS, Institute of Physics, The Energy Institute and The Royal Society of Chemistry. An ASTM Eagle award recipient, Dr. Shah recently coedited the bestseller, “Fuels and Lubricants handbook”, details of which are available at ASTM’s Long-Awaited Fuels and Lubricants Handbook 2nd Edition Now Available (https://bit.ly/3u2e6GY).
He earned his doctorate in Chemical Engineering from The Pennsylvania State University and is a Fellow from The Chartered Management Institute, London. Dr. Shah is also a Chartered Scientist with the Science Council, a Chartered Petroleum Engineer with the Energy Institute and a Chartered Engineer with the Engineering council, UK.
Dr. Shah was recently granted the honourific of “Eminent engineer” with Tau beta Pi, the largest engineering society in the USA. He is on the Advisory board of directors at Farmingdale university (Mechanical Technology) , Auburn Univ ( Tribology ), SUNY, Farmingdale, (Engineering Management) and State university of NY, Stony Brook ( Chemical engineering/ Material Science and engineering).
An Adjunct Professor at the State University of New York, Stony Brook, in the Department of Material Science and Chemical engineering, Raj also has approximately 700 publications and has been active in the energy industry for over 3 decades. More information on Raj can be found at https://shorturl.at/Xm60b and at https://bit.ly/3QvfaLX
Contact: [email protected]
Mr. Mathew Roshan and Miss Madeline Chiappone, are part of a thriving internship alternative energy program at Koehler Instrument company in Holtsville.
[1] Ren, C., Zhang, X., Jia, M., Ma, C., Li, J., Shi, M., & Niu, Y. (2023). Antifoaming Agent for Lubricating Oil: Preparation, Mechanism and Application. Molecules, 28(7), 3152. https://doi.org/10.3390/molecules28073152
[2] Piskura, N. (2023, September 5). Defoamers are chemicals used to control foam in industrial process. ChemREADY. https://www.getchemready.com/water-facts/what-are-defoamers-and-how-do-they-work/
[3] Aikin, A. R. (2025). Webinar. Stle.org. https://www.stle.org/files/TLTArchives/2025/08_August/Webinar.aspx?WebsiteKey=a70334df-8659-42fd-a3bd-be406b5b83e5
[4] Chorus. (2023b, May 17). 3 Types of Defoamers for Lubricant Blending | Chorus Lubriant Additives. Cnlubricantadditive.com; Zhengzhou Chorus Lubricant Additive Co., Ltd. https://www.cnlubricantadditive.com/info/3-types-of-defoamers-for-lubricant-blending-82221160.html
[5] Valvoline. “Sustainable Lubrication in Manufacturing: Best Practices for Optimizing Efficiency and Reducing Waste - ValvolineTM Global Europe - EN.” Valvolineglobal.com, 2025, www.valvolineglobal.com/en-eur/sustainable-lubrication-in-manufacturing-best-practices-for-optimizing-efficiency-and-reducing-waste/.
[6] Noria Corporation. (2018, March 6). Lubricant Additives - A Practical Guide. Machinerylubrication.com; Noria Corporation. https://www.machinerylubrication.com/Read/31107/oil-lubricant-additives
[7] Oestreich, S., Bene, P., & Mangano, J. (2016, January 5). The Role of Molecular Defoaming Actives | 2016-01-05 | PCI Magazine. Www.pcimag.com. https://www.pcimag.com/articles/101514-the-role-of-molecular-defoaming-actives
[8] Abbott, S. (2025). Anti-Foams | Practical Surfactants Science | Prof Steven Abbott. Stevenabbott.co.uk. https://www.stevenabbott.co.uk/practical-surfactants/anti-foams.php
[9] XJY. (2020). silicone defoamer | XJY SILICONES®. Xjysilicone.com. https://www.xjysilicone.com/what-factors-affect-the-performance-of-silicone%20defoamer-5976.html
[10] PMC Ouvrie. (2025, July 15). Defoamer Research & Development - PMC Ouvrie. PMC Ouvrie. https://pmcouvrie.com/research-development/
[11] Chorus. (2023a, February 14). The Main Components Of Chemical Defoamers Are These! - News. Cnlubricantadditive.com; Zhengzhou Chorus Lubricant Additive Co., Ltd. https://www.cnlubricantadditive.com/news/the-main-components-of-chemical-defoamers-are-65830820.html
[12] BYJU’s. (2024). Emulsification - Definition, Examples & Uses of Emulsification. BYJUS. https://byjus.com/chemistry/emulsification/
[13] Romakk. (2023, October 30). Differences in silicone defoamer and non-silicone defoamer. Romakk Silicones - Silicones Delivered Globally. https://romakksilicones.com/what-is-the-difference-between-silicone-defoamer-and-non-silicone-defoamer/
[14] RawSource. (2025, January 29). Silicone-Based Defoamers vs Organic Defoamers: Comparison. Rawsource. https://rawsource.com/how-do-silicone-based-defoamers-compare-to-organic-defoamers/
[15] Adebayo, A. R., Badmus, S. O., Sivabalan Sakthivel, Rezk, M. G., & Babu, R. S. (2023). A systematic investigation of the relationship between properties of bulk foam and foam in porous media. Scientific Reports, 13(1). https://doi.org/10.1038/s41598-023-35278-2
[16] Negar Hadian Nasr, Mahmood, S. M., & Hamed Hematpur. (2018). A rigorous approach to analyze bulk and coreflood foam screening tests. Journal of Petroleum Exploration and Production Technology, 9(2), 809–822. https://doi.org/10.1007/s13202-018-0545-1
[17] Koehler Instrument Company, Inc. (2023, August 4). Products - Koehler Instrument Company, Inc. Koehler Instrument Company, Inc. https://koehlerinstrument.com/products/dual-twin-foaming-characteristics-test-apparatus/?search=D892&description=true&sub_category=true
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