My clothes have white spots after washing. What else can I do except buy another one?

In daily life, convenient and easy-to-use laundry detergent is often the first choice for everyone. Turn on the washing machine, pour in the laundry detergent, and then harvest a pile of clean clothes. But I wonder if you have ever encountered this situation when washing clothes: there are patches of white spots on the washed clothes!

Image source: Xiaohongshu Why is this? To solve this mystery, let’s first understand the main ingredients of laundry detergent.

01What are the main ingredients of laundry detergent?

Laundry detergent is one of the important washing tools in our daily life. It is suitable for all kinds of washable clothes and is mainly composed of surfactants and various additives .

1. Surfactants

Surfactants are the main decontamination ingredients of laundry detergent. How do they remove dirt? This is related to their unique molecular structure. One end of the surfactant molecule is a longer hydrocarbon chain group , which has good lipophilicity and can dissolve in oil but not in water, usually called a lipophilic group ; the other end of the molecule is a shorter polar group , which can dissolve in water but not in oil, usually called a hydrophilic group .

Simple structural diagram of surfactants Source: Baijiahao

Take common oil stains as an example. We all know that water and oil are immiscible, so the oil stains on the surface of clothes cannot be dissolved in water. However, the special structure of surfactants allows its oleophilic end to combine with oil stains and its hydrophilic end to combine with water, so that the stains are effectively wrapped in them .

Decontamination principle diagram of surfactants Source: Baijiahao

With the friction and physical movement during the washing process, stains are separated from the clothes. In addition, surfactants can also reduce the surface tension of water, making clothes easier to be soaked , and then making it easier for laundry detergent to penetrate into the fibers of clothes, enhancing the cleaning effect.

2. Various additives

In daily life, the sources of stains on clothes are not limited to oil stains, there are many other sources, such as dust, dirt, sweat secreted by the human body, etc. No matter what kind of dirt it is, it is usually not a single component, but a mixture of multiple different stains.

Some oily mixed dirt may also undergo complex chemical or physical reactions under the influence of surrounding microorganisms, thereby forming more complex compounds that are more difficult to remove. Surfactants alone are often unable to cope with all washing challenges.

Image source: Xiaohongshu

Therefore, in addition to surfactants, other auxiliary ingredients are added to laundry detergent, which can not only help remove stains, but also enhance the washing effect of laundry detergent to a certain extent, such as making clothes soft and fragrant, whitening and sterilizing. Common additives include: enzyme preparations, pH regulators, water softeners, anti-deposition agents, bleaching agents, softeners and fragrances .

The composition of a laundry detergent. Source: Aiguo

Now that we know the main ingredients of laundry detergent, let’s go back to the question we asked at the beginning.

02 Why does laundry detergent cause white spots on clothes?

The possible reasons are as follows:

1. Excessive use of detergent

Many people have a misunderstanding when washing clothes: they think that the more detergent they use, the better the washing effect will be . However, this is not the case. Too much detergent will cause a lot of foam to form during the washing process. These foams cover the surface of the clothes, making it difficult to wash thoroughly and causing white spots to appear.

Image source: Sohu

Additionally, some laundry detergents may contain strong chemicals that can damage the fibers of your clothing if used in excess, causing your clothing to become thinner or more frayed.

2. Uneven distribution of laundry detergent

When many people encounter stubborn stains, they often soak the clothes in water first, add detergent, and then wash them after a while. They hope that the detergent will dissolve some of the stains first, making it easier to wash them later. But it should be noted that after adding the detergent, the key step is to fully stir the detergent and water. If this step is omitted, the concentration of the detergent may vary, and the areas with higher concentration may appear white.

Image source: iStock

3. Water quality issues

Water quality problems may also cause detergent residue. The water in some places is "hard", that is, there are more soluble calcium and magnesium ions in the water , which may react with the anionic surfactants in some laundry detergents to produce white precipitates that are difficult to rinse off.

Image source: Baijiahao

4. The laundry detergent contains bleach

If your laundry detergent contains bleach and the clothes are not mixed with the detergent during the wash cycle or are not rinsed thoroughly, white spots may remain on the clothes.

Bleach ≠ Fluorescent Agent

Fluorescent agents are often mistakenly believed to bleach clothes and are harmful to the human body, and are often criticized by people. But in fact, fluorescent agents and bleach are two different chemical substances , and they play completely different roles in the washing process.

Bleach is usually an oxidizing agent that chemically reacts with dyes to discolor them. It can remove stains from clothing, but it also removes the color from the clothing.

Fluorescent agent is a fluorescent dye that can emit blue and purple light under ultraviolet light, thereby visually neutralizing the yellow color. Simply put, fluorescent agent relies on optical effects to make clothes look "white" without actually changing the color of the clothes.

Image source: Meipian.com

There is still controversy in academia about the hazards of fluorescent agents. If you have concerns about the use of fluorescent agents, you can choose laundry products that do not contain this ingredient.

5. High temperature washing or clothing friction

Some types of clothing, such as pure cotton , should not be washed at high temperatures, because high water temperatures may cause the cotton fibers to be oxidized by the bleach in the detergent, resulting in whitening. In addition, fragile fabrics such as silk or thin fabrics are easily damaged by friction and may also produce white spots.

Image source: Sohu

After knowing the possible reasons why clothes become white after washing, we understand that the amount of detergent, usage method, water quality and temperature, and washing method may all affect the washing effect.

03 How to avoid and properly handle whitewashing?

First, when using laundry detergent, carefully read its product instructions to ensure that it is suitable for the material of your clothes and use it according to the recommended amount. Secondly, choose the appropriate water temperature and washing method according to the fabric and washing label of the clothes. In addition, it is recommended to mix the laundry detergent and water evenly before washing , so as to ensure a more uniform concentration of the detergent, thereby improving washing efficiency.

Image source: iStock

If the clothes have been washed white, you can consider soaking them in clean water for a while , and then rinse them gently. Or try to use a small amount of laundry detergent to wash the clothes again, using a lower water temperature and a gentle method for a second wash . You can also consider adding lemon juice or white vinegar to the water, soaking the clothes and then washing them. If none of the above methods work, it is recommended to send the clothes to the laundry. References

[1] Sun Huining, Zhang Jian, Shi Jianping. Analysis and research on the decontamination principle of surfactants[J]. Shaanxi Chemical Industry, 2018(5)96-98

[3] Li Lanying, Wei Bin. Requirements for surfactants in laundry detergents [J]. China Detergent Industry, 2009 (5) 75-77 [3] Bi Kai. Discussion on the issue of adding fluorescent agents [J]. Brand and Standardization, 2011 (Z1) 108

Author: Hua Wenyi, Shanghai Science and Technology Museum

Science teacher Science review: Sun Yafei, Ph.D., Department of Chemistry, Tsinghua University, chemical engineer

Editor of this article: Little Dandelion