For wine and handicraft enthusiasts, clay wine jar are not merely containers for storage and fermentation; they are a manifestation of ancient wisdom. The production process of these clay wine jar has been refined over thousands of years through the interaction of natural raw materials, exquisite pottery techniques, and precise control. If you have ever wondered how a simple piece of clay can be transformed into a vessel capable of storing and fermenting fine wine, the following will provide you with a detailed explanation of this process.
- Selection of Clay
The primary principle for making reliable clay wine jar is to select the right clay. Traditional artisans would prefer high-quality kaolin or local clay rich in minerals, which should be free of stones and organic impurities. Such clays possess both the plasticity needed for shaping and the breathability essential for wine aging, which is the key to the jars’ ability to “breathe”.
The preparation process of clay is extremely strict. First, the clay needs to be dried in the sun, crushed and sieved to remove impurities. Then water is added, and sometimes mineral powder is mixed in. The clay is kneaded repeatedly, a process known as “kneading the clay”. Skilled craftsmen can judge whether the air bubbles have been completely expelled through their hands during this process. Residual air bubbles can cause the wine jars to crack. When making high-quality clay wine jars, the clay needs to be aged and further softened to facilitate shaping. This step ensures that the clay, whether made by hand or machine, can maintain its shape and is not prone to deformation.
- Wine jar forming
Shaping determines the size, thickness and structural stability of the wine jars. Nowadays, there are two shaping methods: traditional hand-thrown pottery and modern mold production.
Traditional handcrafting: In traditional handcrafted pottery making, there is a skilled artisan who uses a potter’s wheel to shape a lump of clay into the form of a wine jar. They first center the clay and gradually shape the body of the jar, all the while controlling the thickness of the clay. For larger clay wine jars, pre-shaped clay components may be joined together, and the joints are smoothed with water to achieve a seamless connection.
Modern mold production: To meet the demand for large-scale mass production, artisans use plaster molds. After pouring liquid clay slurry into the mold, the plaster absorbs water and forms a solid clay shell. Then, the excess clay slurry is poured out. When the clay shell is slightly hard, the mold is opened, and uniform greenware of the same size and shape can be obtained. Usually, the mold is also rotated by a machine to ensure that the clay thickness is even and there are no air bubbles.
- Drying
The freshly shaped clay wine jar have a water content as high as 20%, and they are so fragile that they can be broken with just a poke. They cannot be fired directly. The artisans will place them in a cool and well-ventilated area to air dry naturally for 7 to 15 days. Sun exposure or rapid heating should be avoided: this would cause the outer layer of the jars to dry faster than the inner layer, leading to deformation or cracking.
After the wine jars are half-dry, the body of the jars still needs to be trimmed: the artisans will use tools to polish the edges of the jars, trim the necks, and if decoration is needed, they will carve patterns at this stage. Finally, the surface will be gently polished.
- Firing
The core of firing is to control the temperature in stages, and to vitrify the clay through high temperatures. Firing needs to be carried out in a tunnel kiln or a traditional earthen kiln, and both the temperature and duration of firing must be precisely controlled. The firing process involves heating at 1200 degrees Celsius for 12 hours. After firing, the kiln needs to be sealed and the wine jars allowed to cool naturally for several days. A sudden drop in temperature can cause the jars to crack.
- Product quality inspection
A qualified clay wine jar needs to pass strict inspections before leaving the factory. First, the craftsman will hold a lamp to illuminate the jar and check if there are any cracks on its surface. Then, the craftsman will gently tap the outer layer of the jar with a small hammer. If the sound is clear and loud, it indicates that the firing is qualified; if the sound is dull, it means there are flaws inside the jar. Then they will fill the jar with water and let it stand still to check if there is any leakage. If there is leakage, it will be judged as an unqualified product.
FAQ
Why do clay wine jar need to be fired at high temperatures?
Firing at 1,200 degrees Celsius is the key to transforming raw clay into dense and durable ceramics. This process removes moisture from the clay, strengthens the structure of the jar to prevent leakage, and enhances its ability to retain the aroma of wine while inhibiting bacterial growth.
- Can the logo or patterns be customized on the clay wine jars?
Yes, they can be customized. The artisans will engrave the logo, patterns or text on the surface of the jars before firing them.
- How long does it take to make a clay wine jar?
A regular clay wine jar usually takes about a week. A custom-made clay wine jar takes approximately three to five weeks.