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The Secret of Delicate Foam

Published on 18 August 2020

Keeping our hands clean is one of the best ways to avoid getting sick. In recent years, many liquid soap companies have launched the foam version of their products. On one pump, the liquid soap from the bottle turns into the foam in your hands. But why it does not have to be contained in a metal spray bottle with pressurised gas? Is the hand soap specially formulated? Or are there other reasons?

I was eager to find out the answer so I took a foam pump apart. (Figure 1) Besides the tubes and springs which can be seen in an ordinary liquid soap pump, I found a small cylinder which had fine mesh at both ends. If the cylinder was taken away, what came out from the nozzle would only be jets of liquid soap instead of foam. This proved that the tiny cylinder was crucial in the foam making process. (Figure 2 and Figure 3)

After that, I successfully made foam by substituting the mesh with cotton pads, scrub sponge, and even the middle layer of a surgical mask. From our observation, the finer the pores are, the smoother the foam will be. Recently, a foaming body wash which advertises itself as cream-like has hit the shelves. The bottle is unique with the addition of an extra mesh layer at the tip of the nozzle. (Figure 4)

Although the foam pump can produce foam from liquid soap, for consistent foam the water-to-soap ratio of the liquid has to be optimised. If it is too thin, the foam produced cannot hold its form. If it is too thick, the liquid soap may block the mesh and produce no foam. The takeaway of this exploratory teardown is that a trivial thing such as hand washing can become more convenient and interesting with the ingenuity of the inventors.


Figure 1. Structure of a foam pump<br><br><br>
Figure 1. Structure of a foam pump


Figure 2. The upper mesh is finer than the bottom one<br><br>
Figure 2. The upper mesh is finer than the bottom one


Figure 3. Mechanism of foam making<br><br>
Figure 3. Mechanism of foam making

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Figure 4. An extra, fine layer of mesh can form cream-like foam.
Figure 4. An extra, fine layer of mesh can form cream-like foam.
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Please click here for video.
The Science Behind Dalgona Coffee
 
Published on 5 June 2020
 
Coffee is one of the most common beverages. Then what is so special about the trendy Dalgona Coffee? Does the secret of the smooth and frothy foam lie in the caffeine of coffee? Let's find out in the video with Paulina, Museum Director of the Hong Kong Science Museum and Dr. Emily, Assistant Professor of Science Education, Department of Chemistry, The Hong Kong University of Science and Technology!


 


Sea of Spider Tree Flowers in the Urban Areas

Published on 9 April 2020

In springs, my friends always travelled abroad to enjoy beautiful scenery of flowers. But by picking the right time, you can still find beautiful trees and flowers in the urban areas of Hong Kong.

Spider Tree is one of the must-sees. It is a common deciduous urban tree in Hong Kong and may reach 15 metres in height. It has a Chinese name which means "vegetables on the treetop". What is it meant? People in Yunnan province of China pickle the young leaves of Spider Tree as a preserved vegetable. Besides, the wood of Spider Tree is light yet strong, and can be crafted into fish-shaped wooden baits.

Spider Tree has elegant tree form and it flowers from mid to late-April. There are luxuriant flowers clustered at the ends of the branches during blossoming. After the spring rains, I love walking along Prince Edward Road West, Boundary Street or Chatham Road South near the Science Museum to immerse myself in the magnificent sea of creamy yellow flowers of the Spider Trees there. These flowers are quite special if you take a closer look at them. The white coloured petals will turn yellow gradually. Each flower possesses many elongated stamens which are much longer than the petals. The elongated stamens look like the spider legs and this is why the tree gets its name as "Spider Tree".

Planting trees in the urban areas not only beautifies our environment, but is also beneficial to the ecology. The larvae of Great Orange Tip butterflies feed on the leaves of Spider Tree, and that means you have a good chance to see the largest Pieridae butterflies in Hong Kong flying around.

 

The sea of Spider Tree flowers.<br><br><br>
The sea of Spider Tree flowers.


The colour of Spider Tree flowers will change from white to yellow gradually.<br><br>
The colour of Spider Tree flowers will change from white to yellow gradually.

Each flower of Spider Tree possesses ten or more dark red stamens.
Each flower of Spider Tree possesses ten or more dark red stamens.
Great Orange Tip, as its name suggests, has large attractive orange patches on its wing tips.
Great Orange Tip, as its name suggests, has large attractive orange patches on its wing tips.


 


Get to Know the Trees in Hong Kong by Starting with Tree Cotton

Published on 23 Mar 2020

Every year from March to April, the big red flowers of Tree Cotton always catch my eyes when I am strolling along the streets in Hong Kong. Tree Cotton, also known as Red Kapok Tree or Hero Tree, is a flowering deciduous tree with tall and straight trunk that may reach 25 metres in height. Tree Cotton is widely cultivated in Hong Kong and you can find the trees along the road or in the parks in many districts.

Tree Cotton's value is more than meets our eyes. The dried flowers can be used as a Chinese Medicine and is one of the ingredients of the Chinese Herbal Tea. Its tree bark and root are also used as Chinese Medicines for getting rid of heatiness and detoxification. In addition, Tree Cotton contributes much to the local ecology. The nectar produced by its flowers is a delicacy to some commonly seen birds, such as Red-whiskered Bulbul, Crested Myna and Swinhoe's White-eye. They can be found feasting on the blossoming tree. Don't miss the chance to enjoy bird-watching while appreciating the flowers.

When the birds and insects feed on the nectar of the flowers, they unwittingly help the Tree Cotton to pollinate. The pollinated flowers will then grow into 10 to 15-centimetre long fruits. When mature, the fruit capsules burst open and the wind will carry numerous seeds wrapped in fluffy cotton into the air in their search for a new home. In May, we can enjoy the beautiful scene of fluffy flakes drifting down from the trees.

We may not pay much attention to Tree Cotton in the hustle and bustle of our lives. However, Tree Cotton is not completely unknown to us because its heroic image has been mentioned in textbooks and Cantopop songs. Starting from today, let's slow down the pace to appreciate the trees, and admire the beauty of nature!


Flowering Tree Cotton<br><br><br><br>
Flowering Tree Cotton



The seeds wrapped in fluffy cotton are very light in weight, and can be dispersed far by wind.<br><br><br>
The seeds wrapped in fluffy cotton are very light in weight, and can be dispersed far by wind.


Nectar in the flowers of Tree Cotton is a delicacy to the birds.
Nectar in the flowers of Tree Cotton is a delicacy to the birds.
 


 

Last Modified: 20-08-2020

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