Pottery is an art form that is full of charm but also fraught with challenges. From preparing the clay to firing, problems can arise at every stage. Understanding the causes of common problems and knowing how to address them is key to improving the success rate of pottery. Here is a detailed analysis for you.

I. Clay Preparation Stage

(1) Improper Moisture Content of Clay

The moisture level of the clay directly affects the subsequent processes in pottery. Clay that is too dry lacks plasticity and is prone to cracking during throwing or shaping. On the other hand, clay that is too wet is difficult to be shaped and may collapse during drying. Over-dry clay is often caused by a dry storage environment where water evaporates quickly, while overly wet clay results from adding too much water during mixing or insufficient aging.

For clay that is too dry, you can use the spraying method, where you evenly spray water with a sprayer and then wrap and let it sit, or the soaking method, where you soak small pieces of clay in water, drain them, and then knead the clay. For overly wet clay, you can spread it out in a well-ventilated area to allow the water to evaporate naturally, or you can add dry clay powder to adjust the consistency, ensuring that the moisture is evenly distributed when kneading.

(2) Impurities in the Clay

If the clay contains impurities such as stones, sand grains, or wood chips, it can cause the body to crack or break during shaping or firing. This usually happens when impurities are mixed in during mining, processing, and transportation, or when natural clay is not screened. Before use, it is necessary to screen the clay multiple times with a suitable mesh sieve and then knead it thoroughly to improve its plasticity and stability.

II. Throwing and Shaping Stage

(1) Body Deformation

During throwing, it is common for the body to become skewed, twisted, or have an uneven base. The causes include improper throwing techniques with uneven force applied by both hands, inconsistent moisture levels in the clay, inappropriate speed of the potter's wheel, and inappropriate height-to-diameter ratio of the body, leading to an unstable center of gravity.

To address this, you should knead the clay evenly before throwing. Keep your hands steady and apply force evenly, following the sequence from bottom to top and from inside to outside. Adjust the speed of the potter's wheel according to your own habits and the condition of the clay; beginners should not set the speed too high. Reasonably control the size ratio of the body. Slight deformations can be manually adjusted while the body is still wet, while severe deformations require remaking.

(2) Body Cracking

Body cracking is often caused by impurities in the clay, uneven moisture levels, excessive force during throwing, too rapid drying, or collision and compression during the throwing process. To prevent this, ensure the quality of the clay, apply moderate force during throwing, and control the drying environment after shaping by covering the body with a damp cloth or plastic to allow for slow drying. Small cracks can be repaired with slip, while severe cracking requires remaking the piece by kneading the clay again.

III. Decoration Stage

(1) Glaze Peeling

Glaze peeling can ruin the aesthetics and functionality of a piece. It is mainly caused by an unclean body surface, poor glaze formula, improper glazing method, and unsuitable firing temperature. Impurities can affect the adhesion of the glaze, and improper amounts of clay or flux in the formula can cause a mismatch between the glaze and the body in terms of the thermal expansion coefficient.

Clean the body before glazing. Choose the appropriate glaze formula based on the body material and firing temperature, and master the correct glazing methods such as dipping, spraying, and brushing, while controlling the thickness of the glaze layer. Strictly follow the firing requirements for the glaze to control the temperature and the heating and cooling rate. If glaze peeling is severe, you can glaze and fire the piece again.

(2) Uneven Painting Colors

Uneven painting colors, with variations in depth or the appearance of spots and streaks, can result from improper pigment mixing, incorrect brush usage, insufficient painting skills, or an uneven body surface. When mixing pigments, follow the instructions to control the ratio of water to pigment and stir thoroughly.

Choose the right brushes, clean them before use, and maintain consistent pressure and speed while painting, following a logical sequence. If the body surface is uneven, sand it with sandpaper first. You can make timely repairs while the paint is still wet. If the unevenness is severe after drying, you will need to repaint the piece.

IV. Firing Stage

（1）Bubbles and Pinholes on the Glaze Surface

After firing, bubbles and pinholes on the glaze surface can affect the appearance. These defects are caused by impurities in the glaze, coarse particles, excessive glaze thickness, and excessively rapid heating. When preparing the glaze, screen and purify it to control the particle size and apply an appropriate thickness of glaze.

During firing, reasonably control the heating rate, especially during the low-temperature stage, by raising the temperature slowly. Minor defects can be polished out, while severe ones require reglazing and refiring.

（2）Body Cracking and Deformation

Cracking and deformation of the body during firing can lead to a failure. The causes include impurities in the clay, improper formulation, insufficient drying, improper temperature, and uneven heating or cooling.

Choose high-quality clay, formulate it reasonably, and ensure that the body is completely dry before firing. Strictly follow the firing curve to control the temperature and the rate of heating and cooling, and pay attention to the uniformity of the temperature inside the kiln. Minor cracks can be repaired with kintsugi, while severe ones can only be scrapped and remade.

Every step in pottery requires patience and attention to detail. By continuously summarizing problems and solutions, accumulating experience, and being brave in innovation, you can create even better works.