Does Cold Water Rinse Soap Better?


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Typically, when people wash their hands, take a shower, or even clean the dishes, they tend to use warm or hot water. It’s almost natural at this point. But, how do we know if warm water is the most efficient for rinsing the soap off? Could cold water be better? 

There has been no definitive proof that cold water, or hot water, can rinse soap better because there hasn’t been enough research on the subject. However, there is some evidence that the rinsing of soap can be impacted by the hardness of water and water temperature in different ways. 

Below, this article will reflect on the use and effects of soap, the advantages and disadvantages of specific water temperature, and the use of water hardness in relation to which is better at rinsing soap. You will also find information on how the use of specific water types can affect the environment.

Does Cold Water Rinse Soap Better?

What Is Soap?

The best way to understand the effect of water with soap is to first understand the components of soap itself. 

Soap is a combination of fat or oil, water, and alkali that produces a chemical process called saponification. When you go to wash your hands, the soap molecules that were produced act as a mediator between the water that rinses the soap and the oils from the skin of your hands. 

It is crucial to wash hands with soap as it helps prevent the spread of germs. Water alone will not have an effect because it will not interact with the oils on your skin. Water is hydrophilic, and oil is hydrophobic. The two together oppose one another, which is why the soap is needed to act as the mediator. While the soap doesn’t necessarily kill germs, it does remove them from your hands. 

Does Water Temperature Have an Effect on the Soap?

If you think about it, through the years, we have always been told that warm water is more effective for getting rid of germs or getting the grime off of dishes. Basically, we have been told that warm water is the best for everything. But that is simply not true. 

In fact, as was mentioned, there is no definitive proof that warm water is better than cold water, or vice versa, for the rinsing of soap. They each have their own advantages and disadvantages depending on the situation. 

Does Cold Water Rinse Soap Better?

People tend to have a preference for what type of water temperature they like. Some might enjoy a nice cool shower after a scalding hot day, or some may look forward to a soothing warm shower after a long stressful day. But, no matter what your preference, there are always advantages and disadvantages for each. 

Note: In this article, warm, hot water will be defined as 40℃ to 55℃ (104℉ to 131℉).

For example, cold water is associated with less energy absorbance making it more cost-effective for the environment. On the other hand, warm water does use more energy and can further negatively impact the environment because it is more costly. 

Below are some ways that the temperature of the water can have an effect on skin and appliances.

Water and Soap

The temperature of the water can have an effect on the soap. 

Coldwater tends to be better at removing the surface layer of soap as it is more “viscous.” Coldwater can take the contaminants from the surface. 

Hot water has lower surface tension. It can spread easily over any surface. Due to this, it is more practical to use on dishes as it reaches over the entire surface of any dish. It is also better at diffusing the soap. 

Water Can Be a Skin Irritant

It is said that people use warm, hot water 64% of the time when washing their hands. 

Warm water has been found to increase skin irritation as the exposure to higher temperatures can lead to harmful problems for each person. It has also been known to damage the protective barrier surrounding the skin (the skin has many different tissue layers and cells that help to protect it from any damage), which would then cause the skin to be less resistant to the colonization of more bacteria. 

Does Cold Water Rinse Soap Better?

In previous studies, there has also been evidence that linked any exposure to 55℃ (131℉) of up to 30 seconds to result in second-degree burns.  

Water Doesn’t Affect the Spread of Germs: Soap Does

In 2000, there was a Food Production conference held. You might be wondering what that has to do with the use of water. Well, there are laws that guide the water temperature for food workers throughout the states. In this case, the range of temperature was higher than 30℃ (86℉). 

This conference was held to determine if the current water temperature (different in each state) should be changed or to stay the same. 

Every state, excluding one, had determined to lower the guidelines for water temperature, as there had not been enough scientific evidence to keep the hot water temperatures that they had required. They decided to lower the water temperature regulation to 29.5℃ (85.1℉).  

So, then why might have the water temperature guidelines been lowered for each state?

The research that they did utilize in the conference was that warm water didn’t affect the spread of germs. In fact, common pathogens stay alive at temperatures of up to 55℃ (131℉). Further, they found that there was no difference in the removal of bacteria after washing between the temperatures of 24℃ (75℉) to 56℃ (133℉)

In order to effectively remove germs, the warm water would have to be paired with soap. That being said, health organizations do suggest the use of warm water to be used with soap because some soap may emulsify better. 

The Hardness of Water

The hardness of water is determined by the amount of minerals or lack thereof. There are two types: hard water and soft water. Let’s delve into each of their roles.

Hard Water

Did you know that 85% of the U.S. water supply is classified as hard water?

Hard water is water that contains nutrients and minerals such as calcium and magnesium. This type of water is better at binding with the molecules present in soap, and therefore requires people to use less water. However, it is typically harder for soap to lather with the hard water, perhaps due to the amount of minerals present. It gives the soap something to cling to, and it’s easier for soap to wash away. 

Does Cold Water Rinse Soap Better?

There is one significant benefit for using hard water, though – it helps protect people from heart disease and stroke. This is due to the amount of minerals and nutrients that are present in the water. Hard water is better used on the skin, such as washing hands or taking a shower. 

Soft Water

Unlike hard water, soft water does not contain minerals. This makes it harder for it to bind with the molecules of soap, which increases the amount of lather and soap to rinse off. 

Further, soft water’s lack of minerals also means there are more circulatory problems for the blood, and it can interfere with the process of carrying oxygen to our lungs. 

One benefit of soft water is that it doesn’t leave any soap scum (mineral residue) on material items. Soft water is better used for washing dishes, cleaning the house, or doing laundry. 

Conclusion

There is not a definitive answer as to whether cold water is better at rinsing soap. There just isn’t enough evidence or research on the subject. However, there are differences in how warm or cold water interacts with soap and the surface it is on. There are differences in the hardness of water, and how that can affect the rinsing of soap as well.

Jake Alexander

Jake is a freelance writer from Pennsylvania who enjoys writing about science and sports. When he's not writing for Temperature Master, he can be found watching the NFL or playing basketball with his friends.

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