Are you still mixing umbrellas and parasols when the rain and sun come one after another? Stop it →

Many friends complained during the flood season, with heavy rain and high temperatures taking turns, and the words "hot and humid" have become a "nightmare" for many people. In this kind of weather, we are forced to "seamlessly switch" between rain protection and sun protection. Some friends even find it troublesome and only use an umbrella to "go around the world" regardless of whether it is rainy or hot and sunny. So can an umbrella replace a parasol? Today we will reveal the difference between an umbrella and a parasol.

Let me first state the conclusion: they cannot be mixed.

01 Umbrella instead of parasol? Not reliable!

The umbrella itself does not have a sunscreen coating, and the fabric is not as dense as a parasol, so it cannot block ultraviolet rays. Even an ordinary black umbrella will still be very hot under the scorching sun, and because it is not breathable, the perceived temperature will actually rise.

02 How to choose a parasol?

Figure 1 Schematic diagram of ultraviolet spectrum and visible spectrum wavelength (created by the author)

Ultraviolet light (UV) is light with a wavelength of 400nm to 10nm, and can be divided into four types according to the wavelength range: long-wave ultraviolet UVA, medium-wave ultraviolet UVB, short-wave ultraviolet UVC, and extreme ultraviolet EUV.

Among them, UVA rays can cause tanning, UVB has a shorter wavelength and can burn the skin, UVC is generally blocked by the ozone layer, and EUV is absorbed by the Earth's atmosphere [1]. Ultraviolet radiation can cause peroxidation of cell membranes, produce more melanin, and lead to melanin deposition. Ultraviolet rays can be said to be the biggest culprit for skin sagging, aging, dark spots and wrinkles [2].

The selection of parasols usually takes into account the following factors :

Ø Anti-ultraviolet performance : According to the national standard "Evaluation of the Anti-ultraviolet Performance of Textiles" (GB/T 18830-2009), only when the UPF of the sample is greater than 40 and T(UVA)AV is less than 5%, can it be called an "anti-ultraviolet product". In addition, the anti-ultraviolet product should be marked on the label: ①GB/T 18830-2009; ②When 40＜UPF≤50, it is marked as UPF40+. When UPF＞50, it is marked as UPF50+; ③The protection provided by the product may be reduced in the case of long-term use and when stretched or wet.

Ø Fabric : Common parasol fabrics on the market include impact (PG) cloth, polyester cloth, nylon cloth, etc.

Ø Coating : Common coatings for parasols include black glue, silver glue, and colored glue. Black glue is usually attached to the inner layer of the umbrella surface. The material has stable performance, good UV resistance, is not easy to fall off, and has a certain heat insulation effect while blocking light. The price is relatively affordable. Silver glue can be used inside or outside. It has good UV protection and is very cheap. Usually, the cheap parasols sold on the road are basically silver glue coated umbrellas. However, after long-term use, the silver glue is easy to fall off at the folding place, and the protective function is greatly weakened. Colored glue is usually applied on the outside and combined with black polyester cloth. It can basically achieve zero light transmittance and strong UV protection, but it is more expensive. Considering the cost-effectiveness, it is recommended to choose a black glue sunscreen coating with a higher cost-effectiveness.

Ø Color : The darker the color, the more UV rays it absorbs. For example, black, navy blue, and dark green have better UV protection than light blue, light pink, and light yellow [3].

ØUmbrella size : The larger the umbrella, the smaller the area of ​​skin exposed to ultraviolet rays. However, large umbrellas are not very convenient to carry. You can choose a parasol of appropriate size according to your needs.

Figure 2 Sunshades with different coatings sold on the market (made by the author)

03 Parasols instead of umbrellas? Not reliable either!

Frequent exposure to rain will damage the coating of the parasol, especially acid rain, which will damage the coating of the parasol, and the UV protection ability will be greatly reduced when used again. Therefore, it is better to use parasols separately from ordinary umbrellas. If the surface of the parasol is dirty, you can use a soft brush dipped in clean water to gently scrub it. Do not rub it with your hands and do not wash it too frequently, otherwise it will damage the coating and affect the sun protection effect of the parasol.

Of course, if you are walking on the road and suddenly there is a strong wind and heavy rain, and you only have an umbrella in your hand, it is okay to act in an emergency occasionally.

04New umbrella? Are rain umbrellas reliable?

There are many new types of umbrellas on the market, claiming to provide shade on sunny days and protection from rain on rainy days. Are these umbrellas reliable? The Foshan Consumer Council once published an “Analysis Report on the Quality Survey Results of Umbrellas” [3]. All 20 selected umbrellas met the requirements for windproof performance, 5 samples did not meet the requirements for rainproof performance, and 1 sample did not meet the requirements for UV protection performance.

Windproof performance is related to the number of ribs and the material of the umbrella frame. The number of ribs can be 6, 8, 10 or even more. The more ribs there are, the stronger and more stable it is in windy weather. The most common materials for umbrella frames on the market are stainless steel, aluminum alloy, carbon fiber, iron metal, etc. Among them, stainless steel and aluminum alloy have higher strength and do not rust; carbon fiber is light in weight and has a higher price; iron metal is easy to rust and has low strength, and the cost is relatively low.

The main difference in rainproof performance lies in the umbrella fabric. The mainstream fabrics on the market include impact cloth, polyester cloth, nylon cloth, transparent plastic, etc. Among them, transparent plastic, impact cloth and polyester have better rainproof effect and are easy to dry.

When choosing a sun umbrella, you can put it under the sun. The darker the shadow under the umbrella, the better the sun protection effect. You can also put it against the light indoors. The better the shading effect, the better the sun protection performance. And it is best to choose a solid color, because some sun umbrellas have lace around them, or other colors and decorations, and there will be no coating on them, which will affect the sun protection effect.

Judging from the quality of the samples and the selling price, the price cannot directly indicate the quality. It still depends on the specific parameters. It is recommended to always have an umbrella and a parasol at home, carry them according to different weather conditions, and do not mix them. You can also choose a sunny and rainy umbrella with excellent performance in all aspects, which can provide good protection whether it is scorching sun or heavy rain.

Author: Gao Huang, PhD student in Materials Science, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences

Reviewer: Yao Qiaohong, Senior Engineer, PhD, School of Chemistry and Molecular Engineering, Peking University

Produced by: Science Popularization China

References:

[1] Wu Changfeng. “The cause of extreme ultraviolet radiation from solar flares has been found” [N]. Science and Technology Daily, 2020-07-07: 01

[2] Zhu Jiale. “Is full-body sun protection necessary? Experts: Not necessarily, we just don’t need to be exposed to the sun” Yangcheng Evening News, 2024-07-23:A11.

[3] Xu Guoli. Dark-colored sun umbrellas are better than light-colored ones [J]. Fujian Quality Information, 2002, (09): 39-35.

[4] China Quality News Network, the latest survey results of umbrella quality are out! Is the umbrella that protects you from wind and rain reliable? [EB/OL] (2021-03-12) [2024-08-23].https://www.cqn.com.cn/ms/content/2021-03/12/content_8672506.htm