Detailed explanation of the brushing glaze process for ceramic mugs

Xin xiang ceramic mug manufacturer, brushing glaze is an important process in glazing ceramic mugs. This process is characterized by high flexibility and a long history of use. In some cases, it is necessary to use the brushing glaze process when glazing mugs. However, this process requires high technical skills and has high production costs.

1. What is glazing?

Glazing, as the name suggests, is a method of “brushing” glaze onto the surface of a ceramic body with a brush (similar to a calligraphy brush or paintbrush). We have seen furniture being painted, but this is ceramic glaze being applied to ceramic mugs. It is one of the oldest, most direct, and most flexible methods of glazing. Unlike “dip glazing,” which involves immersing the entire body in glaze slurry, or “spray glazing,” which requires advanced equipment, brush glazing is akin to an artist painting a picture, applying the glaze layer by layer.

2. Applications of brush glazing

Brushing glaze is done by hand, so it is inefficient but highly flexible. Therefore, brushing glaze is suitable for ceramic mugs that are not produced in large quantities and for small orders. Because brushing glaze is highly flexible, this process is also suitable for ceramic mugs with complex glaze requirements, such as ceramic mugs with handles and bodies of different colors, or ceramic mugs with gradient colors on the body or handle. Brush glazing is also suitable for ceramic cups with multiple layers of glaze. For example, ceramic cups with wood grain, floral patterns, stone patterns, etc. on parts of the cup body, or ceramic cups with glitter glaze. Because brush glazing is usually done with a brush or paintbrush, it is also very suitable for repairing areas where glaze has been smeared or sprayed (such as the handle connection, cup rim, cup bottom, etc.). In addition, the brush glazing process is often used for complex mug shapes. For example, the brush glazing process is used for mugs that are too large, too small, or have complex shapes.

3. What is the brush glazing process?

3.1. Prepare the glaze slurry: Mix the glaze powder and water in a specific ratio and stir to a consistency similar to thick cream or yogurt. If the mixture is too thin, it may flow unevenly; if too thick, it may be difficult to apply and leave heavy brush marks. “Instructions for Making Glaze in Ceramic Mugs”

3.2. Prepare the body: Make sure that the mug body waiting to be glazed is completely dry (called “raw body”) and that the surface is clean and free of dust and oil stains. Typically, they undergo a “plain firing” process (What is the plain firing process for raw ceramic mugs? ) to make them sturdy and less prone to breakage, making it easier to absorb water (better glaze adhesion).

3.3. Glazing steps:

Glazing technicians hold a brush (commonly a wool brush or soft-bristle brush) and dip it into an appropriate amount of glaze slurry. Like painting, the glaze is evenly applied to the surface of the body. The direction of brushing should be consistent or cross-brushed to ensure full coverage. For mugs, pay special attention to the rim, the connection between the handle and the body, and the bottom rim, which are areas where glaze is easily missed or accumulated. Both the outer surface and inner cavity of the mug need to be carefully brushed. The glazing process usually requires 2-3 coats or even more to achieve the desired glaze thickness and even coverage. During multiple glazing applications, pay attention to the time intervals: After applying the first layer (base glaze), wait until the surface is slightly dry before applying the second layer. If the glaze surface is too wet when applying the second layer, it may damage the first layer, resulting in uneven glaze or peeling.

After glazing is complete, the ceramic mugs should be inspected and repaired: Carefully check whether the glaze surface of the ceramic mugs is uniform, and whether there are any missed spots, bubbles, or obvious brush marks. If there are any problems, repair them with a pen in a timely manner. Finally, place the glazed mugs on a drying rack to dry naturally, avoid touching them, and wait for them to be fired in the kiln. “In-depth analysis of the firing process of ceramic mugs” .

4. Pre-glazing and post-glazing work

4.1. Pre-glazing preparation:

Body preparation: Ensure that the green body is completely dry, cooled, and free of dust and grease (use a soft brush or compressed air to clean). Inspect the body for defects (cracks, pores), which must be repaired before glazing.

Glaze slurry preparation: Accurately measure the glaze materials and water according to the formula, mix thoroughly (preferably sieve) to the desired consistency, and let it settle to remove bubbles. Stir again before use.

Tool preparation: Prepare clean, appropriate brushes (different models may be needed for different areas), containers for holding the glaze slurry, stirring rods, clean water (for washing brushes), and racks for holding unglazed and glazed greenware (to prevent contact between pieces).

Operator preparation: The operator’s hands must be clean and dry. Understand the characteristics of the glaze slurry (such as drying speed) and the desired effect.

4.2. Post-glazing preparation:

Handle with care: Glazed pieces are extremely fragile (the glaze layer has not yet been fired), so they must be handled and placed with extreme care to avoid any bumps or fingerprints/scratches on the glaze surface.

Thorough drying: Place the glazed mugs in a well-ventilated, dust-free, safe (no people walking around and touching them) place to dry thoroughly and naturally. The drying time depends on the humidity of the environment and the thickness of the glaze layer. Make absolutely sure that they are completely dry before putting them in the kiln! Residual moisture will turn into steam when the kiln is heated, causing the glaze surface to crack and even the body to explode.

Final inspection: After drying, carefully inspect the glaze surface again for cracks, peeling, dust impurities, missed areas, or excessive buildup. Minor defects can be attempted to be repaired by gently sanding with extremely fine sandpaper (e.g., 800 grit or higher), but large-scale issues may require washing off and reapplying the glaze.

The glazing process is a test of the technician's experience. The quality of the glaze is usually determined by high-quality glaze materials, fine techniques, and strict management. With more than 20 years of professional ceramic mug production experience, China Ceramic Mug Factory has many experienced glazing technicians. We adhere to the concept of “details are fundamental, quality is life” to provide customized ceramic mugs for our customers.

Detailed explanation of the glaze spraying process for ceramic mugs

Xinxiang ceramic mug manufacturer, spray glazing is a surface treatment technique used in the production of ceramic mugs. A spray gun is used to atomize the glaze into tiny particles, which are then evenly sprayed onto the surface of the ceramic blank. Glaze is a glass-like coating that, when fired, gives ceramics smooth, waterproof, and wear-resistant properties, while also serving a decorative purpose. Spray glazing is suitable for complex shapes (such as unconventional mugs) or ceramic mugs that require fine gradation effects. Compared with traditional dip glazing, it allows for more flexible control of glaze thickness and coverage.

1. Spray glazing operation process

The spray glazing process is more advanced than dip glazing. Currently, ceramic mug factories commonly use two types of spray glazing processes: manual spray glazing and automatic spray glazing. Manual spraying requires a spray gun and air pump. The technician holds the spray gun, keeping it 20-30 cm away from the mug, with an air pressure of 0.3-0.5 MPA, and moves the spray gun at a constant speed, first covering the edges and recesses, then spraying the entire surface to ensure an even glaze layer. Complex areas (such as the inside of the mug handle) need to be sprayed repeatedly. Automatic assembly line operation: Place the ceramic mug blank upside down on the rack and send it to the conveyor belt. When the rack moves the ceramic mug under the spray gun, it rotates at a constant speed for 2-5 seconds (the dwell time is determined according to the different glaze materials and requirements) to spray the glaze. After spraying the glaze, check the ceramic mug blanks. If there are any areas missing glaze, use a brush or sponge to fill in the glaze. Finally, clean up the excess glaze at the bottom of the blanks to prevent them from sticking to the kiln plate during firing.

2. The difference between spray glazing and dip glazing

Operating method: Glaze spraying relies on equipment for application, while glaze dipping involves directly immersing the green body into glaze slurry to absorb it. In automated production lines, the cost of glaze spraying and glaze dipping lines differs.

Applicable scenarios: Spraying glaze is suitable for complex shapes or partial glazing (such as mugs with transitional colors); dipping glaze is suitable for simple shapes and ceramic mugs with low glaze color requirements. Dipping glaze is highly efficient but not as good as spraying glaze in terms of detail.

Glaze layer effect: Spray glazing can control the thickness of the glaze layer to achieve gradations or textures; dipping glazing produces an even glaze layer but tends to accumulate glaze on the edges.

Cost and difficulty: Spray glazing requires equipment investment and high operating skills; dipping glazing is low in cost and suitable for the production of conventional ceramic mugs.

3. Precautions fspray glazing

or The spray glazing process uses a spray gun to apply glaze to ceramic mugs. The glaze slurry has strict requirements. If it is too thick, it will clog the spray gun, and if it is too thin, it will not provide sufficient coverage. In addition, the glaze slurry needs to be stirred regularly to prevent sedimentation. The spray gun needs to be thoroughly cleaned after each use to prevent residual glaze from clogging the spray gun and to prevent residual glaze from being sprayed onto the greenware after drying, causing debris to fall on the ceramic mug. During the glaze spraying process, avoid spraying at a fixed point for a long time (which can easily cause glaze flow). The key is to coordinate the movement speed of the rack with the air pressure of the air gun. Additionally, workers in the spraying workshop must wear masks and goggles to avoid inhaling glaze dust.

4. Preparation before spraying glaze

Body treatment: After drying, the ceramic mug body must be completely cooled, and surface dust must be removed with compressed air.

Glaze Preparation: Adjust the glaze slurry. For specific instructions, please refer to “Instructions for Making Glaze in Ceramic Mugs”

Test spraying: Test spray on scrap clay or bisque-fired pieces to observe glaze adhesion. Adjust the rotation speed and time of the stand, as well as the air pressure of the spray gun.

5. Post-glazing treatment

After spraying the glaze, the raw ceramic mug needs to be dried. During the drying stage, the raw mug should be kept out of direct sunlight or strong winds, and it is best to dry it naturally in the shade for 6-12 hours (depending on the humidity). After applying the glaze, the glazed surface needs to be inspected, mainly to observe whether the glaze is uniform under strong light, with a focus on checking areas prone to leakage, such as the handle connection and the rim of the mug. In addition to inspection, the glaze on the bottom of the mug should be removed so that the part of the ceramic mug that comes into contact with the kiln plate remains free of glaze. Finally, the ceramic mug blanks are placed on the kiln plate with spacing between them and wait to be fired in the kiln.

6. Six major defects that are likely to occur

6.1. Uneven glaze surface

Some substandard colored glazed ceramic mugs have uneven glaze thickness on the surface, which can be distinguished by the naked eye. The orange peel glaze phenomenon of ceramic mugs that we discussed earlier is a relatively obvious example. For the specific causes of this issue, please refer to “Research and Solutions for the Orange Peel Glaze Phenomenon in Ceramic Mugs”  .

6.2. Glaze cracking

After the ceramic mug is glazed and dried, cracks appear. These cracks are mainly divided into horizontal, vertical, and mesh patterns. The main reasons for this are: a. The glaze layer is too thick (>0.5mm) or the glaze has been sprayed multiple times. Because the glaze layer is too thick, cracks are likely to appear on the glaze surface during the drying stage of the ceramic mug. b. The ceramic mug dries too quickly during the glazing and drying stage. The main reasons for this are that the temperature in the drying workshop is too high or there is a strong wind blowing directly on it.

6.3.  Grainy glaze surface

There are obvious bumps on the glaze surface of the ceramic mug. The main reason for this phenomenon is the glaze. The glaze is too coarse, and the particles in the glaze slurry are sprayed onto the ceramic mug. Another reason is that the spray gun is not cleaned regularly, causing the previous glaze to clump together and be sprayed onto the ceramic mug.

6.4. Glaze flow

This phenomenon is similar to the first type of uneven glaze surface. Glaze flow mainly occurs at the bottom and rim of the mug. If we disregard the glaze itself and only consider the glazing process, then local glazing will lead to glaze flow.

6.5. Pinholes/bubbles

Pinhole and bubble defects in ceramic mugs during the glazing process are mainly caused by bubbles and impurities in the glaze, or dust on the greenware.

6.6. Glaze peeling

If the glaze peels off a spray-glazed ceramic mug, there are two possible causes. There are two reasons for this: one is that the green body is contaminated with oil or dust; the other is that the moisture content of the green body is too low. This prevents the glaze from adhering properly to the green body, causing the glaze layer to peel off.

Spray glazing is a process that is often used when customizing ceramic mugs. This process has obvious advantages when dealing with mugs of special shapes and mugs with special requirements for the glaze surface. The essence of good glaze spraying lies in the combination of “standardization” and “refinement.” From raw material selection and glaze preparation to the glazing process, every step is controlled by the people at Xinxiang Ceramics Factory. China Ceramics Mug Factory believes that only by converting process parameters into executable SOPs and continuously optimizing every detail can the best balance between efficiency and quality be found.

Ceramic mug dip glaze process details

Xin xiang custom ceramic mug manufactuer, in the previous section we talked about the phenomenon of orange peel glaze on ceramic mugs. One reason for this is the glazing process. Our common ceramic mugs are glazed, professionally this kind of mug is called color glaze mug. Many people said, we see the color glaze mug very little ah, are like: sublimation mug, printing mug, travel cup, stoneware mug, etc.. In fact, these ceramic mugs have a layer of glaze on the body, strictly speaking, they all belong to the color glaze mug. Only, on the basis of color glaze mugs, they have their own independent characteristics, so they are named after their characteristics. Well, let's talk about the glazing process of ceramic mugs, the glaze developed into a glaze paste, attached to the ceramic mug billet process, called glazing. Common glazing methods include dip glaze, spray glaze, brush glaze, pouring glaze and so on. Today we focus on a talk: dip glaze process.

1. Glaze before the preparation

Before the formal dip glaze, ceramic mug factory is to do some preparatory work. The purpose of these preparations is to ensure the success of the glazing process, reduce the rate of defective products. These preparations are mainly divided into 4 parts:

1.1. Clean ceramic mug raw blanks

In the previous article we will have, after the clay made of ceramic mug billet, to carry out the “Ceramic mug clay billet drying and billet repair process”  During the drying process, the blanks may be dusted. If the dust on the mug is not cleaned up, then the adhesion of the glaze is reduced and the ceramic mug we get in our hands is prone to problems. In this process, the raw blanks need to be cleaned with an air gun. At the same time, but also to detect the water content of the raw ceramic mug, the most suitable glaze water content is: 3% -5%. Raw billet water content is too low, it will be excessive water absorption, damage the structure of the glaze; water content is too high is prone to pinholes, flowing glaze and other problems.

1.2. Raw ceramic mugs

Whether the raw ceramic mugs should be plain fired, we have explained in the previous article. “What is plain firing of raw ceramic mugs?”.  Some ceramic mugs with complex shapes or special requirements for the thickness of the mug, need to be fired before glazing. Vegetable firing process, can enhance the quality of the ceramic mug billet, in the later glaze, hand-painted, paste underglaze flower paper and other processes, is essential, this link is not all ceramic cups, only for high-end ceramic cups.

1.3. Prepare glaze

Quartzite, feldspar, kaolin, after powdering, sieving, mixing slurry, etc., made of glaze paste, these specific operations in the “glaze raw materials, production, classification and quality” explained in detail. Before glazing, the glaze paste should be stirred and tested, mainly checking the color and fluidity of the glaze paste.

1.4. Cleaning the workshop

The glazing workshop in a ceramic factory is cleaned separately before formal glazing. It is the same as ceramic mug raw cleaning, in order to guarantee the cleanliness of the glaze on the ceramic mug. The main thing is to clean up the dust, control workshop temperature and humidity. Workshop temperature is generally controlled at about 25 ℃, humidity control at about 50%.

2. Ceramic mug dip glaze

2.1. Basic principle

Utilizing the water-absorbing properties of ceramic mug blanks, the surface is uniformly adhered to by immersing the glaze paste, similar to the principle of painting oil paintings. The glaze paste penetrates into the pores of the ceramic mug under capillary action, forming a 0.2-0.3mm thick glaze layer.

2.2 Scope of application

Dip glaze on the shape of the ceramic mug is required, regular cylindrical, conical ceramic mugs, using dip glaze. Dip glaze because the operation is simple, with automatic dip glaze equipment, for large orders, often used dip glaze process.

2.3 Operation steps

Mechanical arm grips the upper edge of the mouth of the mug at 1/3, the raw billet is vertically immersed in the glaze paste, keep the glaze surface 5mm away from the mouth of the mug, hold it for 2 seconds, and then lift it away from the glaze surface at an even speed. After lifting, the mechanical arm rotates 3-5 turns at 60 rpm to shake off the excess glaze. During this process, keep the mouth of the mug tilted downward by 15 degrees to discharge the accumulated glaze using gravity.

3. Drying and finishing

3.1 Drying

After glazing, place the raw ceramic mugs horizontally on the grid drying rack, and require the ambient temperature to be about 25℃ and humidity to be about 50%, drying for 2 hours. Then, raise the ambient temperature to 40℃, humidity 30%, and activate the circulating fan to accelerate the drying for 5 hours.

3.2. Finishing

Use sponge, scraper and other tools to clean up the mouth and bottom of the mug, excess glaze.

4. Quality Inspection

Grade A standard: glaze without pinholes, bubbles (diameter <0.2mm); thickness fluctuation <±0.05mm; mug roundness error <0.3mm.

5. Common Problems

5.1: Glaze accumulation at the mouth of the mug (“glaze circle”)

Causes: insufficient rotating speed of dumping glaze / too deep immersion glaze

Countermeasures: Increase the speed to 80 rpm; install limiters to control the depth of immersion.

5.2: Lack of glaze on the handle

Causes: Air bubbles attached / Mechanical arm clamping obscured

Countermeasures: ultrasonic vibration to remove bubbles before dipping glaze.

5.3: Glaze layer peeling off

Phenomenon: after drying the glaze appears spider web cracks

Root cause treatment: adjust the glaze paste formula (add thickener)

5.4: Uneven thickness

Means of detection: every 30 pieces with a thickness gauge sampling test

Process optimization: the specific gravity of glaze paste is stabilized at 1.45; add automatic replenishment pump to maintain a constant liquid level.

5.5: Glaze pollution

Pollution source tracking: 60% from workshop dust; 30% from impurities in the glaze tank.

6. Analysis of advantages and disadvantages of glaze dipping method

6.1 Core advantages

Outstanding efficiency: single machine handles 800-1200 pieces per hour

Low cost: the utilization rate of glaze material＞95%.

Stable quality: pass rate up to 92%-95%.

6.2 Inherent limitations

Weak adaptability: not suitable for relief/shaped mugs

Edge defects: the mouth of the mug needs to be processed twice.

The immersion glaze method is still the mainstream glazing process for ceramic mugs after centuries, and its essence lies in the combination of “standardization” and “refinement”. As the old craftsman said: “dip glaze three points by equipment, seven points in the management.” Even the most sophisticated equipment, but also need people to manage. The production of ceramic mugs is a process of detailing. From raw material selection, glaze preparation to glaze process, each link has Xinxiang ceramic factory people on the details of the control.  China ceramic mug factory believes that the only way to find the best balance between efficiency and quality is to transform the process parameters into enforceable SOPs and continuously optimize every detail.