Xin xiang Ceramic Mug Manufacturer, ceramic factories use a variety of methods to shape ceramic raw materials into ceramic mugs. The two most frequently used methods are press molding and grouting molding. As the names suggest, these two processes involve different steps and use different equipment. They are also suitable for different types of ceramic mugs. Let me explain the specific differences between them.

1. What is grouting molding

Grouting molding is a process used to make ceramic mugs. This process involves using a mold to shape liquid ceramic slip into ceramic mug blanks. There are two methods for shaping ceramic mug blanks. the first is press molding, which I have previously discussed in an earlier article (Ceramic Mug Molding Production Process Details), and the second is slip casting. Grouting molding to make ceramic mugs is like making ice cubes with silicone molds. There are many types of molds used for grouting molding, but the most commonly used are plaster molds. Simply put, liquid ceramic slurry (technically called “greenware” or “slurry”), which is like thick milk, is poured into this plaster mold. The plaster acts like a sponge, quickly absorbing the moisture from the slurry. The slurry near the inner wall of the mold gradually changes from a liquid to a solid layer of clay as the moisture is absorbed, just like a layer of clay slowly “growing” on the inner wall of a mug. When this layer reaches the desired thickness (such as the thickness of a mug wall), pour out the excess slurry that has not yet solidified inside the mold. Finally, allow the wet clay shell remaining in the mold to continue to dry, harden, and shrink a little, then carefully open the mold and remove the molded wet blank (the unburned prototype of the mug). Therefore, the core of this process is to use gypsum to absorb water and allow the slurry to “stick to the wall” and solidify.

2. What kind of mugs are suitable for grouting molding

Due to the characteristics of the raw materials and molds used in grouting molding, the type of ceramic cups suitable for this process is very clear. The higher the fluidity of the ceramic slip, the stronger its plasticity. In addition, there are many different mold styles, and production is simple. Therefore, slip casting is suitable for ceramic mugs with complex shapes. In Christmas gift shops, we often see various styles of ceramic coffee mugs, such as animal ceramic mugs (with cute kittens, puppies, etc. inside) and ceramic mugs with pipes. Because these mugs have special shapes, they can only be made through slip casting. In addition, this process is also suitable for making embossed ceramic mugs, ceramic mugs with different handles, etc. Finally, this process is also suitable for making very large ceramic mugs with a large capacity, such as oversized ceramic beer mugs, which are not suitable for compression molding and can only be made by slip casting.

3. Slip casting molds

Gypsum molds are mainly used to make ceramic mugs. Why is gypsum used to make them? The answer is actually very simple: it is highly absorbent, inexpensive, and easy to make. The inherent properties of gypsum allow it to quickly and uniformly absorb moisture from the ceramic slurry, enabling the slurry to form quickly according to the mold's shape. However, gypsum molds also have drawbacks. Their main drawback is that gypsum is easily damaged, and gypsum molds have a short service life. After multiple uses, the mold's absorbency decreases, and residual ceramic slurry in the mold is difficult to clean.

4. Grouting molding operation steps

Step 1: Assemble the mold & prepare the grout: Assemble the two halves (or multiple pieces) of the dry, clean plaster mold tightly together, secure them with rubber bands or clamps, and ensure that there are no leaks at the joints. At the same time, ensure that the grout has been mixed to a consistency similar to thick cream, stirred evenly with no bubbles.

Step 2: Pouring the slurry: Pour the slurry into the opening at the top of the mold (usually corresponding to the mouth of the mug) until the entire mold cavity is filled.

Step 3: Absorbing slurry (water absorption and curing): Let the mold filled with slurry sit for a period of time (possibly 15 minutes to 1 hour, depending on the size of the mold, the age of the plaster, and the characteristics of the slurry). During this time, the plaster mold acts like a sponge, absorbing water from the slurry starting from the inner walls. The slurry near the inner walls of the mold transforms from a liquid into a solid layer. The longer the time, the thicker the layer.

Step 4: Return the slurry (pour out the excess slurry): When the mud layer reaches the desired thickness (for example, 5-6 mm for a mug), turn the mold upside down and pour the excess slurry that has not yet solidified back into the slurry bucket for recycling. At this point, a layer of “mud shell” will be evenly attached to the inner wall of the mold.

Step 5: Consolidation & Moisture Control: After draining the excess slurry, continue to leave the mold (with the opening facing down or tilted) for a period of time. This allows the moisture within the clay shell to be further absorbed by the plaster, while the moisture inside the clay shell gradually distributes evenly, making the clay shell more robust. This stage is crucial for minimizing deformation and cracking.

Step 6: Open the mold and remove the blank: When the clay shell becomes strong enough (like the hardness of soft leather), carefully loosen the clamp and gently separate the two halves (or multiple pieces) of the plaster mold. At this point, a complete, wet ceramic mug blank will be exposed.

Step 7: Repair the blank & dry: Carefully remove the wet blank from the mold (sometimes an air gun is needed to help remove it from the mold). Then trim the blank: use a wet sponge or small tool to remove the mold line, trim the rim, handle joint, and other areas. Finally, place the blank in a well-ventilated, evenly dry place to dry naturally until it is completely dry (called “raw blank”) before sending it for bisque firing (What is the plain firing process for raw ceramic mugs?).

5. Grouting molding vs. pressure molding

Different principles: Grouting molding: Liquid clay slurry flows into the mold, and the gypsum absorbs water and solidifies to form the shape. This creates a “shell.” Press molding: A solid clay block (clay segment) is placed into the mold (typically metal), and a rotating gypsum head (rolling) or metal template (spinning) is used to compress and roll the clay against the inner or outer walls of the mold to form the shape.

Different molds: Slip casting: Mainly uses water-absorbing gypsum molds. Compression molding: Mainly uses metal molds (steel or resin), which are very strong and durable.

Suitable products: Slip casting: Has an absolute advantage in complex, irregular shapes, deep carvings/reliefs, complex handles, large pieces, or thick-walled mugs. Can be done in small batches. Press molding: Absolute advantage in mugs with regular, symmetrical (round/oval) and relatively simple shapes. Particularly good at fast, large-volume production of standardized mugs.

Production efficiency: Slip casting: Slow. Requires waiting for water absorption, curing, and drying. Only one mug can be made at a time with one mold (or several if it is a combination mold). Mold lifespan is short. Press molding: Fast, extremely high! Machines can press a blank in seconds to tens of seconds, with an extremely long mold lifespan (tens of thousands to hundreds of thousands of cycles).

Cost: Slip casting: Mold costs are low (plaster is inexpensive), but per-unit labor/time costs are relatively high (due to multiple steps and lengthy processes). Press molding: Mold costs are high (metal molds are expensive), but per-unit production costs are extremely low.

Green body quality: Slip casting: Green body density may be slightly lower (due to particle deposition), and drying shrinkage may be slightly greater. Surface detail reproduction is extremely high. Press molding: Green body density is high, strength is good (due to compression), and drying shrinkage is relatively small. The surface is smooth, but the ability to reproduce complex details is inferior to slip casting.

Labor dependency: Slip casting: More dependent on skilled workers, especially in the blank repair stage. Press molding: Can be highly automated, with labor mainly involved in loading, unloading, and inspection.


Slip casting and press molding are the two most commonly used ceramic mug manufacturing processes. When customizing ceramic mugs with special shapes, ceramic mug factories will choose to use slip casting; Conversely, if customizing ordinary mugs, only special colors (Instructions for making glaze in ceramic mugs) or special images (What kind of ceramic coffee mugs are not dishwasher and microwave safe?), then mold forming is chosen. Therefore, the shape of the ceramic coffee mug you hold in your hand determines its manufacturing process. Of course, both processes are mature technologies in ceramic factories, and the quality of ceramic mugs still depends on the quality of raw materials and process management. For more detailed information on press molding, please refer to: Customized Ceramic Coffee Mugs - Grouting Process Explained