Advanced Age Signs

Dead Glaze Bubbles as advanced Age Sign

"Dead bubbles" can be used for verifying the age of antique Chinese ceramics. It concerns two different types or eras, general glazes and more ancient glazes, as explained for Jun glazes.

First we need to be aware that basically all glazes of Chinese ceramics contain bubbles. This can sometimes be used for age verification. Here we mention "dead" bubbles.

(Type 1)  Ming/Qing dynasty glaze bubbles:  
After a long time of use some bubbles close to the glaze surface may develop a tiny hole (not visible to the bare eye). Bubbles in contact with crackles inside the glaze can also develop such.
Again, after a long time some of these tiny holes change into straight tiny cracks (also invisible without magnification). Still later these straight crack become cross-shaped ( a vertical and a horizontal crack). These minute openings can get infiltrated by dirt from the environment over time (not all do). This results in the bubble interior turning to a dark color. They are then called "dead bubbles" presumably because they are bubbles no more.
As it takes a very long time for bubbles to reach this stage, this can be a sign that the glaze is really old.

Please note however, that at present it is not yet possible to tell for sure from what era or period a glaze with dead bubbles is; it is only an indication that the item is old/antique. (There is still further research needed. Each glaze type may be different.)

(Type 2)  Ancient ceramics from the Yuan/Song dynasties -- Jun glazes:
This concerns mainly specific glazes, like for example Jun glazes, but this is not valid for each item, or may be dependent on the kiln. This is still in research.
Basically, Jun glazes are said to develop new bubbles for about 60 years after firing.
These items are hundreds of years older and may have bubbles in a more advanced stage of deterioriation than the dead bubbles in earlier dynasties. After bubbles crack a tiny whole in the process described above, the whole bubble may burst open. Such glazes can show more or less severe pitting over the whole or part of a glaze. In this case the pitting that developed from burst bubbles is visible with the bare eye. Due to the time it takes to reach this stage, this means an item would be older than one that has not pitting, but some glazes perhaps never reach this stage due to a different glaze composition.

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