The number of people using smartphones is increasing, and to protect their beloved devices, manufacturers of phone cases and screen protectors have earned quite a bit. However, accidents are inevitable in life. If you're not careful, a scratch may appear on your phone screen—scratching the screen, hurting the owner's heart. To solve the problem of scratched screens on their beloved phones, users have tried every possible method, leading to various rumors. Among these, the most widely circulated repair method is that toothpaste can fix scratches on phone screens.\
\Why can toothpaste repair scratches? The editor collected related explanations online, mainly based on the following two points (the principles of the two claims are different):\1. The silicon-containing substances in toothpaste can fill in scratches;\2. The abrasives in toothpaste can polish out minor scratches. Toothpaste contains abundant abrasives, which can polish and repair fine scratches on phone screens.\So, are these two claims valid? First, let's look at the components of toothpaste: \Toothpaste is a complex mixture. It usually consists of abrasives (such as calcium carbonate, dicalcium phosphate, calcium pyrophosphate, silicon dioxide, aluminum hydroxide), humectants, surfactants, thickeners, sweeteners, preservatives, active additives, as well as pigments, fragrances, etc. (Via Baidu Encyclopedia)\According to netizens, the substance that can "repair" is the abrasive (making up about 20%-50% of the toothpaste). An abrasive refers to very fine particles in toothpaste, and according to national standards, the particle size of abrasives is approximately 10μm-20μm. Common abrasives in toothpaste include: calcium carbonate (CaCO3), dicalcium phosphate dihydrate (CaHPO4·2H2O), silicon dioxide (SiO2), aluminum hydroxide [Al(OH)3], etc.\
\Different toothpaste formulas use different abrasives. For example, in the U.S., dicalcium phosphate and silicon dioxide are commonly used as abrasives, while in China, calcium carbonate is mostly used. Therefore, it is more likely that calcium carbonate is the substance "filling" the scratches.\OK, assuming the abrasive in toothpaste is silicon dioxide, then can it fill the scratches on a phone screen?By looking up toothpaste abrasives, we know that the particle size of abrasives in toothpaste is generally around 10μm, usually not exceeding 20μm. Some abrasives, such as light calcium carbonate, have particle sizes generally between 1μm and 3μm, while the smallest size visible to the human eye is about 50μm. In other words, scratches are much larger than toothpaste abrasive particles, and it is difficult for these particles to firmly fill the scratches through friction alone.\So, can abrasives be used to polish small scratches on a screen? From the physical properties of commonly used fillers in toothpaste, the hardness of solid calcium carbonate and silica is around 7, which is comparable to the hardness of glass screens. Theoretically, these two substances could potentially help polish the screen.\However, the calcium carbonate and silica used as toothpaste abrasives are processed light calcium carbonate and low-hardness composite silica. This is because the Mohs hardness of human tooth enamel is about 5-6, so the industry standard for toothpaste requires that substances used as abrasives have a Mohs hardness of less than 5. It is generally believed that a Mohs hardness of around 4 is suitable for toothpaste abrasives, so toothpaste cannot polish glass screens with higher Mohs hardness.\
\Toothpaste is rich in abrasives to protect teeth\Why do some netizens think this way? Perhaps it is because of an advertisement by a certain toothpaste brand: experimenters rubbed another brand of toothpaste on an acrylic sheet and observed many tiny scratches under a microscope. However, for toothpaste manufacturers, they have special equipment called a toothpaste hardness tester to measure the hardness of abrasives. The test method is to rub 5 grams of toothpaste on a glass slide 100 times; if traces are left, it is considered unqualified. This shows that using an advertisement as evidence is indeed not very reliable.\It is also worth noting that when polishing with toothpaste, if there are tiny sand particles (Mohs hardness = 7) or other impurities in the environment or on the polishing tool (such as a glasses cloth), it may actually make the screen more scratched.\As the saying goes: practice is the sole criterion for testing truth. Although we have analyzed why toothpaste cannot repair screen scratches, adopting a rigorous attitude, we will still conduct an experiment. For convenient filming, we specifically disassembled an iPad screen;The black-circled area on the iPad in the picture is a scratch we found on the screen. We marked the position of the scratch on the back of the iPad screen with a black water-based pen.\
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\We took this photo with a macro lens, and you can see a very obvious scratch.\||
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\Rubbing toothpaste on the scratched area with a finger.\
\After about a minute, wash the iPad screen with water to remove the toothpaste. This is the screen after the toothpaste has been washed off.\Slowly use a paper towel to absorb the water on the screen.\Next...\The moment to witness the miracle has arrived......\Will there still be scratches? Will there?\
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\Unfortunately, the scratch still exists.\Conclusion: Both theory and experiment confirm that toothpaste cannot repair scratches on a phone screen. If any netizens have tried and successfully removed scratches, you can share your method in the comments.
