Why is my oil foaming

Foaming is a common problem with oil-lubricated components. It can be difficult to troubleshoot, and for this reason, accurate testing to determine the root cause of the foaming is essential.

Symptoms

Foam is a collection of small bubbles of air that accumulate on or near the surface of the fluid. In severe cases, the foam can leak out of the machine through breathers, sight glasses and dipsticks. Foam is an efficient thermal insulator, so the temperature of the oil can become difficult to control. The presence of air bubbles in the fluid can lead to excessive oxidation, cavitation, the reduction of lubricating properties of the oil and hydraulic system failure.

Causes

The causes of foaming are many. The most common include:

• Water contamination

• Solids contamination

• Depleted defoamant (possibly due to the use of excessively fine filtration and electrostatic separation technologies)

• Mechanical issues (causing excessive aeration of the fluid)

• Overfilling of the sump with splash- and bath-lubricated compartments

• Cross contamination of the fluid with the wrong lubricant

• Contamination of the fluid with grease

• Too much defoamant additive, either by incorrect formulation or by incorrect reconstruction (sweetening) of the additive package

Measurement

The first tests attempted should be water quantification and particle counting. The formation of air bubbles is often aided by such contaminants, as they provide a nucleation point for the air bubbles. It is important that degassing techniques are used to prepare the fluid prior to the particle count. If you have a foaming problem, the air bubbles in the fluid would otherwise trigger an abnormally high particle count, and that could lead to attempting an incorrect solution.

If the particle count does not reveal any significant contamination, try a patch test using very fine-rated (one micron or less) filter paper. Scrutinize the patch closely under high magnification. You might also want to run a pentane-insolubles test (ASTM D4055-E). This will quantify very fine contamination which can provide nucleation material.

Ask your laboratory to run tests for foam tendency and foam stability. These tests are described by ASTM D892 and are run together. Foam tendency describes the amount of foam generated immediately after the fluid is agitated and aerated, and foam stability quantifies the amount of foam remaining 10 minutes after the cessation of aeration.

The test allows for an “Option A”, which is in place to ensure the defoamant is well mixed and suspended in the lubricant prior to the commencement of testing. This option should be requested for gear oils due to the nature of the defoamant chemistry commonly used in these fluids. Comparison of the tendency and stability can indicate the presence of a mechanical issue, rather than an additive/contamination issue.

Cross contamination of the fluid by another lubricating fluid commonly contributes to foaming and other issues. Additive interferences prevent the defoamant from working properly. To check for this, analyze a sample of new oil from your storage for its elemental signature and compare it to a sample of used oil. The additive signature of the used oil should be similar to that of the new oil, but slight differences (due to additive depletion) are likely.

Pay close attention to elements commonly found in additives (calcium, magnesium, boron, molybdenum, phosphorus, sulfur, etc.) which are present in the used oil but not in the new oil. Also, keep an eye out for elements in the used oil which might indicate grease contamination, if this is possible.

Analyzing a sample of new oil from your storage facility and used oil together will let you know if the component got topped off with the wrong fluid, but it won’t trigger any alarms if cross contamination took place during lubricant formulation or in the storage facility. If you can’t see any signs of cross contamination here, see if you can secure a sample of new oil from a different blending batch.

The use of Fourier transform infrared (FTIR) spectroscopy should also be considered, once again using samples of new oil and the used oil. Advanced analysis of the spectra is necessary. FTIR is particularly useful if fluids with different base stocks have been mixed.

Possible Solutions

Hopefully your testing will have alerted you to some possible reasons for the excessive foaming of the oil.

In almost all cases, an oil change, or at least a partial drain and refill, will be required. If some type of contamination was the root cause, a flush will be required, too. This can become expensive for large-volume systems; so in certain cases, reconditioning of the lubricant may be considered. Be aware that this does not always work, and is likely to be a stay of execution rather than a pardon.

Make sure you address the root of the problem before conducting the drain and flush. For particle and water contamination, concentrate on managing contaminant ingress as far as possible before resorting to filtration. This is particularly important with gear oils where fine filtration can strip the additive from the fluid.

If cross contamination with another oil is the issue, address the solution with fluid identification (color-coding) and training. If grease contamination led to the foam formation, make sure the correct relube quantities and frequencies have been calculated and are being adhered to. Mechanical issues might be due to tank design, oil return-path geometry or suction-side piping air leaks.

Troubleshooting foaming can be a challenging process, but by a process of elimination, you should be able to identify and correct the root cause.

Read more on oil foaming issues:

How to Fix a Foaming Problem

Controlling Oil Aeration and Foam

Eliminate Conditions That Cause Foaming

About the Author

Regarding Coconut oil: I decided to give this a try in my cheapie fryer, because I had done some research into the "least foaming" oil; the longest lasting oil (for regular draining and reuse), and the supposedly healthiest oil to use anyway. What I discovered was, that Coconut oil does seem more prone to foaming, and I have had a couple of incidents of it spewing out over the top of the fryer - whether lid closed or open. I got lots of kitchen paper ready just as a precaution before I used it, but it is still a lot to clean up, as well as being potentially dangerous - firewise. While other types of oil are noted for not foaming, in my case it was usually when using frozen fries that this occurred. Having said that, I found that if I turned the fryer temperature down to 160c at the beginning, left the lid open, and let it foam if necessary for a bit - the foaming then died down, and I was able then to turn it back up to 170c (190c at the end for the "double frying" if desired.) Remember that this was when using the Coconut oil. I get the impression though, that Coconut oil (even if healthier) is not the best/safest oil to use in a fryer like mine. However, one of the reasons for the choice in the first place is that Coconut oil is supposed to be useable and reusable for a very long time, without going off or "rancid". The problem with using frozen "fries" is that the ice on them is water (albeit frozen) and I think this is why THEY are inclined to cause foaming. It might be different with different fryers/types of fryer, but there's an expirimental aspect to such an exercise. The leaving up of the lid in the first place, and the lower temperature at the start seems to work, but the Coconut oil certainly gets pretty near the rim before it settles to a safer level. Apart from these discoveries in practice, and keeping to the aforementioned experience with frozen fries, I think I will be going back to a more conventional oil in future.

What causes oil to foam when frying? Many people don’t understand this phenomenon.

In this blog post, we will discuss the various factors that contribute to oil foaming and give you some tips on how to prevent it from happening.

Keep reading!

Oil might bubble in your pan for a few reasons. Adding water or another ingredient while cooking causes foaming. These liquids break down proteins on the oil’s surface and cause bubbles while frying food.

These bubbles strike other bubbles, generating a greater mess.

What Causes Oil To Foam When Frying?

When food is placed into heated oil, the moisture rises to the surface and evaporates.

This causes the oil to bubble, and when the accompanying moisture, starch, and contaminants are left behind, they may form a foam on the surface.

However, various factors contribute to the formation of foam in the oil, as discussed below:

1. Oil Degradation

Why does oil foam when frying? Bubbles and foam in oil may be caused by oil contamination or deterioration.

When oils are exposed to air, they begin to deteriorate. This is because the oil oxidizes when it interacts with oxygen.

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Oxidation happens when you cook with old oil or fail to properly clean/season your pan before reusing it, which is why you should always fully wipe off your pans before reusing them.

2. The Oil Has Been Overheated

Another cause of this bubbling might be excessive heat. This occurs when you have a hot stove or are cooking at high temps on an electric cooktop.

Once again, this will cause some of the proteins to degrade, resulting in bubbles in the oil.

Furthermore, if you do not reduce the temperature and heat the oil, it will begin to froth.

It is typical to use high heat for the first batch or two, then reduce it for the remaining batches.

As a result, if the temperature is not reduced, the oil may be bubbling.

3. Type of Heating System

Like having too much heat on your stove, sometimes the frying oil heat comes from somewhere else, like fire.

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If you’re cooking with wood or natural gas, some of it may be transported to your fryer, causing bubbling in the oil.

4. The Type of Oil is Incorrect

Why is my cooking grease foaming? Because some oils have lower smoke points than others, choosing the right one for your pan is critical.

The oil’s color before smoking is a good approach to determine its operating temperature.

If it’s clear or light, the oil has a high smoke point and should be safe to use at high temperatures.

When frying with oil, avoid exceeding the smoke point since this will inflict more harm than you intend.

This is why it is critical to understand the smoke point of the oil you are using. If your oil isn’t heated enough, you may also experience bubbling.

In other words, it must be heated before placing food in the pan to cook. If the water isn’t hot enough, the food may begin to froth.

Low-quality oils not designed for deep frying have a high moisture level, which may cause foaming as the temperature steadily increases.

Using the incorrect oil may also alter the flavor of meals.

5. Too Much Batter Or Moisture

Ensure that your food’s batter is not dipping into the hot oil. Overbattering the meal might cause the oil to get foamy if it is overloaded.

Therefore, applying one to two coatings of the batter while battering food is recommended to prevent oil foaming.

If you are not coating your meal with batter, pat it dry before frying it.

This is because excessive water in heated oil produces bubble formation and foaming.

6. Too Much Oil in the Pan

If there is too much oil in the pan, it can cause the oil to foam. Be sure to use the correct amount of oil for the size of your pan.

7. The Oil is Expired

Expired oil can cause the oil to foam. If you are using expired oil, dispose of it properly and do not use it for cooking.

8. The Pan is Too Crowded

The oil will foam if you’re trying to fry too many things at once.

This is because there is insufficient space for the heat to distribute throughout the pan evenly.

The result is an uneven cook and oil that tends to foam.

9. Contact Between Oil and Metal

When you cook, the oil comes into touch with the metal of your pan, which may cause it to froth up due to all the friction and scraping.

How To Prevent Oil From Foaming When Frying

Here are guidelines on how to avoid oil from foaming while frying.

Specific Oil

It is strongly suggested to use an oil designed specifically for deep-frying.

Low-quality oils not designed for deep frying have a high moisture level, which may cause foaming as the temperature steadily increases.

Avoid Heating The Oil Too Much

Be careful not to overheat the oil when frying meals. Once the ideal temperature for frying has been reached, reduce the heat to retain the temperature.

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If the oil is overheated, it will begin to smoke and produce bubbles, resulting in foaming.

It will also alter the taste of the dish. In addition, the meal may burn if the oil is overheated.

Clean and Dry Utensils Before Using

Before using a frying pan, it is necessary to clean it well. Soap and water may be used for this purpose.

After cleaning the frying pan, use a cloth or kitchen towel to dry it since excess water will cause the oil to bubble and produce foam.

This is because leftover soap and detergent may react with heated oil, causing foaming when the meal is fried.

Soap residue may also alter the flavor of food.

Filter Your Oil Before Storing

Filter your oil while it is still cold before putting it in the fryer. Oil naturally contains air, which may cause the foam to build up in your fryer.

If you attempt to filter the oil when it is hot, you will not get as much air out of it as if you filter it while it is cold.

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When you do this, there will be less air mixing in, which will assist in reducing foaming.

When Not in Use, Turn Off Your Machine

The machine components might get hot when you leave your deep fryer on. It may cause your oil to overheat, causing it to burn or foam to flood your vehicle.

When not in use, disconnect or switch off your deep fryer to ensure that the components remain cold and heat normally rather than becoming overly hot.

Drain Any Extra Water In The Food

Before placing any food or ingredients into your deep fryer, ensure they are completely dry.

Similarly, after washing your fryer, dry it well to remove any water droplets that may have remained.

Water and oil do not mix well, so get rid of as much as you can to avoid foaming.

FAQs About What Causes Oil To Foam When Frying?

Do you have any more questions about why oil foams when it’s used to fry?

Here are some of the most frequently asked questions about foams in oil when frying.

Should I Worry If Frying Oil Foams?

Yes. Bubbles in your frying oil suggest it’s broken down and unstable.

If this occurs, the meal may absorb the rancid oil’s taste; therefore, use new oils for frying.

What Should I Do If My Oil Starts To Foam?

If your oil starts to foam, there are a few things you can do to fix it.

First, you can try lowering the temperature of the oil. This will help stop the oil breakdown and prevent further foaming.

Final Verdict

So, what causes oil to foam when frying? Foaming oil can be caused by high temperatures, drops of water in the oil, the wrong oil type, or contamination.

So now you know why oil foams when you fry something. Use the right oil temperature the next time you fry and don’t put the food in the pan too soon after turning off the oil.

Remember to follow the tips above to keep oil from getting foamy when you fry. Best of luck!