One reason for the tea coaster's lack of attention is the fact that not all tea cultures use them, in fact, most in Asia don't. Japanese teaware mainly focuses on matcha and the ceremony surrounding it and coasters are not necessary in the gong fu setup of China where cups are usually set right on the tea table or a tea tray. In Japan and in China, when they do use them, they often prefer metal coasters. Out of all the teawares that could be made of metal, the tea coaster is, from a Feng Shui perspective, the best place for metal in the arrangement of teaware. It acts to balance all the elements on the table by anchoring (or controlling) any excessive energies that might be present. From this view, having metal under the tea cup makes perfect sense.
In Korea, because of the way teaware is arranged, the coaster is commonly used. Koreans rarely use metal coasters or any metal in their arrangement of teawares. You do see beautiful ceramic ones in use though. These pieces by artist Park Sung Il are real beauties...
These modest pieces are a good example of the natural beauty of Korean wares.
Firstly, they are functional. They are of the appropriate size which hold most Korean cups which tend to be larger that Chinese teacups but smaller than Japanese teacups. The top surface is slightly slanted towards the center so as to not allow the spilt tea to drip off the coaster. It also has four cute little legs which prevent a hot tea cup from transferring heat to whatever is underneath the coaster as well as giving it stability.
The shape of these coasters, although very simple, are quite beautiful. The shape has a quality about it that feels as thought it has just blossomed or formed. It gives the tea coasters the feeling of a cloud in the sky or the outside pedals of a blossoming flower. But it does so in a such a subtle way as not to draw attention away from the cup that sits atop, and the tea that rests in that cup. In this way these tea coasters teach one modesty when drinking tea.
The white colour of these pieces convey a sense of peace, purity, and simplicity. The colour white, although not a metal, vibrates with the frequency of metal- in some ways imitating its affect on the energy of the set up. Due to the nature of buncheong style teaware, these white coasters haven't retained their pure white look. They have darker cracks that are only brought out through usage. This is what gives them such natural beauty.
This beauty also teaches one a deep lesson. Although the purity of white is beautiful in its own, it can only stay pure if unused or if no tea touches its surface. If unused its even more beautiful state of infinitely small intricate pattern of cracks will never be revealed. Only though a subtle mistake, some sort of slightly careless action, or imperfect action can its true beauty be revealed.