Let’s look at some Jianzhan that have rusted, as shown in the image below. Has your Jianzhan also experienced rusting?
1. Why does Jianzhan rust, and which parts are prone to rust?
It is widely known that the patterns on the surface of Jianzhan mainly consist of precipitated iron crystals. The composition of these iron crystals is iron, which easily oxidizes into brown iron oxide when exposed to air.
If the Jianzhan is soaked in tea or not dried properly after use, the water vapor can oxidize the iron into iron oxide. Iron oxide appears as a reddish-brown color, commonly known as rust.
The key factor influencing rusting is the presence of crystal precipitation on or under the glaze. A successfully fired Jianzhan will have the glass layer perfectly covering the crystals, resulting in a smooth glass-like surface when touched. This is known as crystal precipitation under the glaze.
On the other hand, if the crystals are located above the glassy layer (or if a good glassy layer has not formed), appearing on the surface of the glaze, it is called crystal precipitation on the glaze. The crystals on the glaze lack the protection of a glass layer and direct contact with air leads to rust formation.
The cup’s rim is thin, and the glaze layer is thinner, making it more prone to crystal precipitation on the glaze. So, the cup’s body is directly exposed to the air, making it more susceptible to rusting.
2. What do you do with Rusted Jianzhan?
Firstly, rusted Jianzhan does not affect its usability. If you don’t notice any strange taste while using it to drink tea, you can continue to use it without concern.
Secondly, if you wish to treat the surface of the cup to remove rust, try soaking the cup in vinegar and then scrubbing the surface with a rough cloth before rinsing it with clean water. Repeat this process several times to remove mild rusting issues.
Lastly, whether a Jianzhan cup is prone to rusting is determined during its firing process. If the glass layer formed is thin and cannot provide sufficient protection, the cup will be more susceptible to rusting. This is an irreversible process. You can only try to maintain the cup and slow the rusting process.
3. How to store to prevent rusting?
1) After drinking tea, rinse the cup with hot water to remove any tea residue on the glaze. Then, thoroughly clean the cup with clean water and place it in a well-ventilated area to air dry. You can also use a dedicated tea cloth to wipe it clean.
2) Avoid storing the cup in damp areas or immersing it in water, even if it is well-vitrified. Keep it dry.
3) Avoid using corrosive cleaning agents to clean the cup.
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