Can you take away all the dirt with just one spray? Another day of being cheated by short videos

If you often visit Douyin, you must have been recommended these things (all IQ taxes):

Silk protein blackhead removal

Dehumidifying foot patch

Cleansing foam that sprays clean

This kind of kitchen and bathroom cleaning agent is quite attractive. Regardless of whether you really need it or not, first of all, it looks very "cool" and is very friendly to people with obsessive-compulsive disorder.

But after actually spending the money to buy it, I found that the effect is completely different from what is shown in the video!

Is it that there is something wrong with the product in the advertisement?

More foam does not necessarily mean better use

The biggest visual impact in the video is the bubble effect. Most people buy detergents for the cleaning power of the foam, but unfortunately, the cleaning effect of the detergent is not closely related to the bubble effect.

The formation of foam in water can only mean that there is a lot of foam. The ingredients of the cleaning agent reduce the interfacial tension between water and air, resulting in the liquid being able to produce more surface area, making it easier to form foam.

Image source: Wikipedia

The true strength of the cleaning power depends on whether the cleaning solvent has a strong enough dissolving effect on the dirt on the object being cleaned (that is, a chemical reaction). If it can completely dissolve the dirt, the cleaning effect will be very good. Even if it cannot be completely dissolved, the binding force between the solvent molecules and the dirt must be greater than the binding force between the dirt and the object being cleaned.

Adding detergent only creates conditions for the formation of foam. If you want a large amount of foam, it is not enough to just reduce the interfacial tension between water and air. A large amount of gas must enter the liquid. In the video, a large number of bubbles are produced without any external mechanical action. This is obviously impossible unless a chemical reaction occurs to produce a large amount of gas.

In layman's terms, the products we buy cannot directly spray out so much foam, and even if there is a lot of foam, it does not mean that the cleaning power is strong.

Cleansing power depends on ingredients

If you want good cleaning ability, you can't just look at the "visual effect", but mainly look at the ingredients.

Even seemingly ordinary cleaning agents may have excellent stain removal capabilities. For example, the surfactants in the most widely used dishwashing liquid are very effective cleaning ingredients.

Image source: Wikipedia

The structure of surfactant is very special. One end of it is a polar hydrophilic group, such as carboxyl, hydroxyl, amino, etc., and the other end is a non-polar lipophilic group, such as alkyl, aryl, etc. The lipophilic group is a molecular structure with a relatively long chain length, while the hydrophilic group is relatively short, like a match. As shown in the figure:

Image source: "Introduction and Analysis of Surfactants"

It is this structure that gives it the special function of being both hydrophilic and lipophilic.

When they are added to water, the lipophilic groups are responsible for "grabbing" the non-polar oil molecules, and the hydrophilic groups are responsible for "grabbing" the polar water molecules, ultimately achieving the dispersion of non-polar substances in water (polar solution).

Although this situation is not true dissolution, because of this special encapsulation effect, substances with different polarities can be evenly dispersed to form a microemulsion state, which is transparent or translucent, and can be stable for a long time without stratification, which is similar to the effect of dissolution.

That is to make the oil soluble in water, so that the water can take away the dirt. Most of the cleaning agents we use are based on this principle.

If the surfactant has a better "wrapping" effect on the stain, the "solubility" will be poor, and it will be easy to settle. The part that is not "dissolved" and dispersed during cleaning will still remain on the surface of the cleaned object. (Is it the slogan of "removing stains without residue"?)

If a surfactant wants to have a good solubilizing effect on stain molecules, it needs to have more molecular structures that can "grab" the stains.

So in addition to the surfactant as the main ingredient, there are some auxiliary ingredients in the cleaning agent, which we can call builders, to deal with different oil pollution situations.

A cleaning agent ingredient list

For example, when we clean some stains containing polyvalent metal ions, the metal ions may act on the surfactant component to make it ineffective. At this time, adding inorganic salts such as sodium hexametaphosphate and sodium tetraphosphate can chelate with the polyvalent metal ions in the water, thereby avoiding the ineffectiveness of the main ingredient surfactant. It also has a certain effect on decontamination itself, because sodium phosphate salts are conducive to adhering to the surface of the stain, greatly increasing its surface charge and preventing it from copolymerizing and re-depositing.

Therefore, if a cleaning agent wants to clean the complex stains in real life, it needs multiple ingredients to work together. The polarity of the stain components is different, and the cleaning agent components that really work on them are also different.

It is basically impossible to achieve universal cleaning, unless it can dissolve everything in the world. If that were the case, there would be no question of whether your bathtub is clean or not, and it might just disappear into thin air.

Choose a cleaning agent based on the type of dirt

Although it is impossible to make a universal cleaner, Tadpole can still give you some reference suggestions when dealing with different stains in life.

Image source: Wikipedia

Trust the merchant's classification

To clean organic stains, such as cooking oil, motor oil, paint, ink, etc., alkaline detergents are generally chosen, which have a better cleaning effect on organic matter.

To clean inorganic rust stains, deposited scale, etc., acidic cleaning agents are generally chosen because they can more easily clean metal ions deposited on the surface.

To clean biological stains, such as blood stains, fat, etc., enzyme cleaners are generally chosen, which can specifically decompose proteins, fats, starches, etc.

Select organic solvent

Of course, in daily life, businesses have generally done targeted classification, but sometimes, they still cannot achieve the cleaning effect we want, such as the refreshing feeling in the video.

At this time, according to the principle of like dissolves like, if water and detergent cannot solve the problem, we can also choose organic solvents and choose solvents with a closer polarity to the polarity of the stains to be cleaned.

For example: alcohol, ethyl acetate, acetone, n-heptane, etc. When choosing organic solvents, remember to choose those with relatively high purity, easy to evaporate, and preferably colorless and transparent, so that after cleaning, they can evaporate quickly by themselves and will not form new stains on the surface of the object.

Complex stains

If the composition of the stain itself is complex, such as lipstick stains, paint, colored juice, etc., generally speaking, to clean such stains, you need to follow the organic and inorganic methods first. First, use an organic solvent to clean the main body of the stain, and finally treat the remaining pigment with an acidic or enzyme cleaner, which can clean it more thoroughly.

Therefore, there is no universal cleaner. Different types of stains must be removed by choosing corresponding types of cleaners. Have you learned how to buy them?

END

Review expert: Sun Yafei, Ph.D. in Chemistry from Tsinghua University.

Tadpole Musical Notation original article/reprint please indicate the source

Editor/Xiao Xitushuo