General Information on Microscopic Identification
For a long time since the beginning, identification of ancient ceramics are only using traditional eye view method. But in recent years, with the help of science and technology, porcelain imitation level rise at an alarming level, and the traditional identification method is facing severe challenges.
Today, to catch up with the rise of imitation, there are many methods surfaced for dating authenticity, and mostly are done in laboratory. All have different advantages and disadvantages. One of the cheapest method and can be done instantly and easily is through microscopic identification of bubbles. With just a good portable microscope with 60x magnification (recommended) or 200x magnification if you want to pin point, the world of microscopic phenomena reveals.
Porcelain, after hundreds of years, changes occur and will certainly leave marks/traces on the inside of the glaze, and these marks/traces that we can perceive, can not be copied. Make up can only conceal the external. However, no matter how good the makeup artist is, still powerless if comes for internal substantive.
It is known that varies of bubble size, layer, number, layout and color intensity, not only can give a good assistance to distinguish a genuine artifact from revival copy or a modern, but also can roughly determine various periods. Like for example, generally accepted conclusions, most Yongle porcelain is characterized by 'large, medium and small bubbles in mixed layout' or Ru is characterized by ‘very few bubbles’.
Bubbles are present in all antique Chinese porcelain and the size, layout and number of the bubble varied greatly depending on the period the item was produced. It is correlated with the composition of the paste and glaze, moreover, composition of the paste usually has microscopic minerals in it like copper or iron which will oxidized further in the prolong of time and this morphing sometimes can be seen inside the glaze too. It is also correlated with pigments used for the decoration and the thickness of it. However, the different forms of fuel affecting bubble the most.
As we know, several forms of fuel have been used for firing, like wood, coal, gas and electric. Wood fired was the most difficult in maintaining the ideal temperature. Since it was not easy to control, fluctuation always occur, therefore in most wood fuel, the bubbles varied greatly in sizes and very sparsely and unevenly layout. Halos sometimes can be seen on some bubble as well as wrinkles and flashing on the glaze surface. On the other hand with gas fired, because of well controlled temperature and using industrial made paste, the bubbles are incredibly tiny and very uniform in sizes and layout. The bubbles are even tinier, almost unseen, and more uniform if fired with electric.
Other important criteria about bubble is the coloured bubble. Colour intensity of the bubble has many degree starting from slight yellow to black. It sometimes can become green or red too, after hundreds of years, if react with oxidized minerals surrounding it. Colour, through hand touch, soil, and flood, can seep into bubble through nano opening, nano burst and cracks. Gas in the bubble will gradually lost and slowly replaced. But it takes a very long time to make the bubble to attain colour. For example, there is no coloured bubble found in late Qing or Republic pieces. Bubble started to attain colour, light yellow, only after mid Qing onwards and the longer the time, the darker it can be.
It is still unknown why bubble study not made popular in the West, but in the opposite, very popular in Chinese antique porcelain communities and Chinese net. Try type in "Glaze bubble identification", translate it to Chinese, copy paste, search, and auto translate back or just look at the images. there are wealth of information in it.
Lastly, tips in learning microscopic identification is to know what to look inside the glaze. Discovering previously unseen microscopic phenomena can be very fun. Share any view on microscopic identification with other collectors akin. Long observation and more research in the long run can yield perfect judgement. Hope this will trigger the emerging of many porcelain microscopic identification communities in the near future.