Xinxiang Ceramic Mug Manufacturer, in the previous article, “Causes and solutions for running glaze in ceramic mugs,” when discussing glaze running in ceramic mugs, we mentioned in Section 4, “Which shapes of mugs are more prone to glaze running,” that special types of mugs usually use swing glazing for the interior glaze. Today, we will talk about swing glazing. Swing glazing is a glazing technique used in the manufacture of ceramic mugs. This method is mainly used on the inner walls of ceramic mugs.

1. What is swing glaze?
Glaze swing is also a method of applying glaze, similar to Dipping Glaze (Ceramic mug dip glaze process details) and Spraying Glaze (Detailed explanation of the glaze spraying process for ceramic mugs) and Painting Glaze (Detailed explanation of the painting glaze process for ceramic mugs), Pouring Glaze (Detailed explanation of the pouring glaze process for ceramic mugs), which are also types of glazing. Unlike other glazing techniques, glaze pouring is mainly used on the inner walls of ceramic mugs. During the process, workers pour a certain amount of glaze slurry into the interior of a dry, bisque-fired ceramic body. They then hold the body with their hands or using equipment and shake, tilt, and rotate it in various directions. This utilizes the glaze slurry's own fluidity and centrifugal force to evenly “drip” the glaze across the inner surface of the ceramic body. Imagine you are holding an empty mug and want to evenly coat the inside of the mug with sugar water. What would you do? You would probably pour in some sugar water, then gently shake and rotate the mug to allow the sugar water to flow inside the mug, covering every inch of the surface, and finally pour out the excess sugar water. Glazing is the application of this principle to ceramics! This is a method mainly used to apply glaze to the inside of vessels (such as mugs, bowls, vases, etc.). Finally, the excess glaze slurry is poured back into the glaze bucket for recycling. The key to the whole process is the “swinging” action, which allows the glaze slurry to flow and cover the inner wall like water waves.

2. Preparations before glazing
Before the actual glazing process, the ceramic mug factory needs to do some preparatory work. The purpose of these preparations is to improve the success rate of the glazing process and reduce the rate of defective products. These preparations are mainly divided into four parts:
2.1. Cleaning the ceramic mug blanks
In the previous article, we mentioned that after the clay is made into ceramic mug blanks, it is necessary to carry out “Drying and trimming process of ceramic mug clay blanks”   Ash may fall on the blanks during the drying process. If the dust on the mug is not cleaned, the adhesion of the glaze will be reduced, and the ceramic mug we hold in our hands will be prone to problems. In this process, an air gun is needed to clean the greenware. At the same time, the moisture content of the ceramic mug greenware needs to be tested. The most suitable moisture content for glazing is 3%-5%. If the moisture content of the greenware is too low, it will cause excessive water absorption and destroy the structure of the glaze; if the moisture content is too high, it is easy to cause problems such as pinholes and glaze flow.
2.2. Bisque firing of ceramic mug greenware
We have already explained in detail in previous articles whether ceramic mug greenware needs to be bisque fired. “What is the plain firing process for raw ceramic mugs?”  Ceramic mugs that are glazed should preferably be bisque fired. The bisque firing process can increase the strength of ceramic mugs and stabilize their water absorption rate, which are the two foundations for successful glazing. What problems will arise if glazing is applied to ordinary greenware instead of bisque-fired ceramic mugs? Glazing on raw clay is extremely difficult technically, with extremely demanding requirements for the clay body, glaze slurry, operating process, and drying conditions, which can easily lead to high breakage rates and glaze defects. Raw clay has a very high water absorption rate, and there are significant differences in the water absorption speed of different parts (such as the thickness of the mug wall). Additionally, when glaze slurry is applied to the green body, it can cause uneven water absorption, leading to deformation of the green body and uneven glaze surfaces.
2.3. Preparation of Glaze Materials
Quartz, feldspar, and kaolin are ground into powder, sieved, and mixed into a slurry to form the glaze slurry. These specific processes have been detailed in “Raw Materials, Production, Classification, and Quality of Glaze Materials” . Before glazing, the glaze slurry must be stirred and tested, primarily to check its color and flowability.
2.4. Cleaning the workshop
The glazing workshop of a ceramic factory needs to be cleaned separately before formal glazing. This is similar to cleaning the greenware of ceramic mugs, in order to ensure the cleanliness of the glaze on the ceramic mugs. The main tasks are to clean up dust and control the temperature and humidity of the workshop. The workshop temperature is generally controlled at around 25°C, and the humidity is controlled at around 50%.

3. Glazing Process
After completing the preparatory work as described above, the actual glazing process begins:

3.1. Pouring the glaze: Workers hold the greenware (such as a mug) and pour an appropriate amount of glaze into it. The amount is critical. Too little will not cover the entire piece, while too much will be wasted and easily flow to places where glaze should not be applied (such as the outer rim or bottom of the mug).

3.2. Shaking/Rotating (Glazing): This is the core step! Workers swiftly and skillfully use wrist and arm movements to shake the greenware up and down, left and right, and front and back, while simultaneously tilting and rotating it. The goal is to make the glaze slurry flow and wash against the inner walls of the greenware like waves, ensuring every corner is covered to form an even glaze layer. This process is typically very quick, completed in a few seconds to a dozen seconds.

3.3. Draining Excess Glaze Slurry: Once the inner walls are uniformly coated, the clay body is immediately tilted (usually inverted) to drain all excess glaze slurry not absorbed by the clay body back into the glaze bucket. This step must be executed decisively and cleanly to prevent glaze slurry from accumulating at the rim or flowing onto the outer walls.

3.4. Cleaning the rim: After draining the glaze slurry, it is usually necessary to quickly wipe away any remaining glaze droplets from the rim of the body using a sponge or finger to prevent the rim from being stuck by glaze (kiln sticking) or affecting the appearance after firing.

3.5. Drying: After applying the interior glaze, the body is left to dry in preparation for the next steps (such as dipping or spraying the exterior with glaze).

4. When is dipping glaze suitable?
Due to the special nature of the dipping glaze process, it is only suitable for applying glaze to the interior of vessels. These vessels include ceramic mugs, ceramic bowls, ceramic jars, ceramic vases, etc. Applying glaze to the interior of these ceramic vessels is challenging, so the glaze dipping method is employed. Through glaze dipping, the interior of deep and narrow vessels, particularly the bottom and corners, can be effectively covered. These areas are difficult to treat using conventional spray glazing or dip glazing. Glazing is done entirely by hand, and skilled workers can more easily produce perfect ceramic products by controlling the concentration of the glaze slurry, the glazing time, the angle, and the force. This is because ceramic products themselves are works of art, including daily-use ceramics, ceramic mugs, etc. With the advancement of technology, machines have replaced manual labor, and automated assembly lines can produce more uniform ceramic products. However, this also reduces the artistic sense of ceramic products.

5. The difference between glazing, dipping, and spraying
Earlier, Xinxiang Ceramics Factory explained in detail several glazing techniques for ceramic mugs, including dipping, spraying, brushing, and pouring. The main glazing techniques for ceramic mugs are dipping and spraying, so what is the difference between glazing and these techniques? When we customize ceramic mugs, when should we choose dipping glaze, under what circumstances should we choose spraying glaze, and what kind of ceramic mugs should use splashing glaze?

In fact, through our previous knowledge, we can also roughly understand the characteristics of these three glazing techniques. In order to give everyone a more thorough understanding, Xinxiang will compare the three glazing techniques horizontally. Dip glazing is usually used to treat the exterior of ceramic mugs or the exterior and interior of conventionally shaped ceramic mugs, while spray glazing is usually used to treat the exterior of ceramic mugs and the interior of conventionally shaped mugs, especially those with complex shapes (Unusual mugs, embossed mugs, Gradient glaze mug) on the outside of ceramic mugs. Glaze splashing is usually used to treat the inside of ceramic mugs, that is, to apply glaze to the inner wall of the ceramic mug. Conventional mug types can be treated with glaze splashing, but it is inefficient and wastes a lot of glaze. Only ceramic mugs with unconventional shapes can be treated with glaze splashing. Glazing is currently done manually by pouring glaze into the ceramic mug and rotating and shaking it to coat the inner wall with glaze. It consumes less glaze than spraying but more than dipping.

6. Summary
Glaze slurry coating is a key manual process in ceramic mug production that focuses on glazing the inner walls. It utilizes the fluidity of the glaze slurry and ensures that the deep cavity is evenly coated by pouring, shaking, and pouring out the excess glaze slurry. For mug production, glaze slurry coating is the most comprehensive method for treating the inner walls of mugs. Its advantages lie in its good coverage of complex internal structures and relative savings in glaze material, but its efficiency depends on the skill of the worker. For the outer wall of the mug, depending on the product design (whether a uniform color is required, whether a pattern is required, whether a special effect is required) and production requirements, either dipping (high efficiency, low cost) or spraying (more flexible, rich effects) is chosen to complete the process.