Reasons for the deformation of ceramic tableware after use

The deformation of ceramic tableware after use may be caused by the following reasons:

Problems in the design of product modeling

Unreasonable center of gravity and structure: If the center of gravity of the product is not properly handled, resulting in a situation where it is heavier at the top and lighter at the bottom, or if the shape is too high or too long, the thickness and size of each part are inappropriate or uneven, or the clay is improperly stored, etc., all these may cause the ceramic tableware to deform after use. For instance, some ceramic cups with overly slender shapes may deform due to unstable center of gravity and structural issues after being filled with hot water.

Design defects of the rim and belly: Unreasonable design of the product shape, such as insufficient thickness of the belly of the vessel, too small bottom diameter, unreasonable structure at the turning point of the folded edge, excessive extension of the folded edge in all directions, improper thickness and position of the accumulated clay, etc., may also lead to deformation. Bowls with thinner mouths and shallower bellies may be more prone to deformation during use.

The issue of billet formula

Clay usage and loss on fire: If the amount of highly malleable clay in the body is too large and the loss on fire is too large, it will cause excessive drying shrinkage and firing shrinkage, thereby leading to deformation of ceramic tableware. For instance, some low-quality ceramic tableware may show obvious deformation after being used for a period of time due to an improper proportion of clay in the raw material formula.

The amount and composition of flux: If the amount of flux in the billet is too large and the Al₂O₃ content is too low, the amount of liquid phase in the billet at high temperatures will be excessive and the viscosity will be low, which can also easily cause deformation. In addition, if the expansion coefficients of the body and glaze are not properly matched, it will also cause the ceramic tableware to deform after use.

Problems with the billet preparation process

Raw material processing: The presence of air or impurities in the raw materials, insufficient mixing, stirring and refining, and short aging time may all affect the quality of ceramic tableware, leading to deformation after use. For instance, if the impurities in the green body are not removed thoroughly, during the firing and usage processes, these impurities may affect the structural stability of the green body, thereby causing deformation.

Moisture and particles: Excessive or uneven moisture in the green body, overly fine green body or unreasonable particle gradation, and particle orientation arrangement, etc., will also increase the risk of deformation of ceramic tableware. For instance, uneven moisture in the billet can lead to inconsistent shrinkage during the drying and firing processes, thereby causing deformation.

Forming process problem

Equipment and operation: If the forming pressure is too low or too high, the forming equipment is of poor quality and has excessive vibration, the clay is not added properly during the rolling, spinning, and plastic pressing forming processes, or the operations such as forming, trimming, and glazing are improper, all these may cause defects in the ceramic tableware during the forming process and make it more prone to deformation after use. For instance, unstable forming pressure may lead to uneven density of the green body, causing it to deform due to uneven force application during subsequent use.

Model and grouting: Uneven dryness and wetness of the model, uneven drying temperature with the mold, forced demolding or demolding too late, improper demolding operation, overly fine particles, inappropriate density, and poor stability of the grouting slurry used, etc., will also affect the forming quality of ceramic tableware, leading to deformation after use.

Drying treatment problem

Drying system and speed: Improper control of the drying system, excessive drying speed, and uneven drying of various parts of the body may all cause internal stress in ceramic tableware during the drying process, thereby leading to deformation after use. For instance, if the drying speed is too fast, the surface of the green body may dry out while the interior still contains a considerable amount of moisture. During subsequent use, the evaporation of the internal moisture will cause uneven shrinkage of the green body, leading to deformation.

Placement method: If the body is placed unevenly or the placement method is inappropriate, it may also affect the drying effect, and subsequently cause the ceramic tableware to deform.

Problems with the processes of loading the blanks and the kiln

The moisture content of the clay body and kiln furniture: If the moisture content of the clay body entering the kiln is too high, or if kiln furniture such as saggars and shelves with low structural strength at high temperatures are used, or if the inner bottom of the saggars used is uneven or cracked and no pads are used, or if the pads are uneven or contain impurities, it may affect the stability of ceramic tableware during the firing process, leading to deformation after use.

Loading the body and the saggar column: If the body is not loaded properly or vibrates during handling, the bottom part of the body may deviate from the pad cake, causing the lower stack to shift. During firing, the body may tilt to one side due to uneven shrinkage. If the saggar column is not kept flat, stable and straight, it may also cause the ceramic tableware to deform.

Firing process issues

Temperature difference and temperature rise inside the kiln: Excessive temperature difference at various locations inside the kiln, too rapid temperature rise during firing, excessively high firing temperature, and excessive high-temperature holding time may all cause excessive thermal stress in ceramic tableware during the firing process, thereby leading to deformation after use. For instance, excessive temperature differences within the kiln may cause uneven heating of different parts of the ceramic tableware, resulting in different shrinkage rates and subsequently leading to deformation.

Issues regarding the usage environment and methods

Temperature change: When ceramic tableware is used to hold liquids that are too hot or too cold, due to the principle of thermal expansion and contraction, it may deform. For instance, directly pouring hot water into ceramic tableware just taken out of the refrigerator, or directly pouring boiling hot water into cold ceramic tableware, may cause it to deform due to the sudden change in temperature.

Uneven force distribution: During use, if ceramic tableware is subjected to uneven external forces, such as collision or compression, it may also cause deformation. For instance, if multiple ceramic tableware are stacked together in an improper way, it may cause the tableware at the bottom to be subjected to excessive pressure and deform.