Xin xiang Ceramic Mug Manufacturer, in the last post, we explained clay aging, this link is simple but important. Is clay the only thing that needs to be aged during the entire ceramic mug production process? The answer is no. Similar to painting in the “white” of the “aging” link, throughout the production process of ceramic mugs. Clay, glaze, mold, billet, glaze, firing, these processes are inside the “aging” link. So, today let Xinxiang ceramic mug factory, to the whole ceramic cup production process perspective, explain the “aging” link.

1. clay aging
clay aging, commonly known as “stuffy material” or “trapped mud”, it is not simply to mix the mud pile on one side regardless. It is a controlled process of storing the vacuumed clay in a specific environment for a certain period of time.
You can think of it as the “waking” process of mixing noodles. When the dough is made and covered with a damp cloth and left to rest for a while, it becomes softer, more elastic and more malleable. The resulting pasta is both full and flavorful. Aging is the “waking up” of the clay. For a detailed explanation, please see: “Ceramic mug clay aging process introduction”.

2. Glaze aging
If clay is the “flesh and bone” of ceramics, then glaze is its “clothes”. If clay is the “flesh and bone” of a ceramic, then glaze is the “garment”. An ill-fitting, unevenly textured garment can ruin the whole look.

2.1 Why age glazes?
To promote the formation and stabilization of glaze colloids: the clay content of glazes forms colloids in water. The aging process allows these colloids to fully develop and stabilize, so that the viscosity and suspension of the glaze paste becomes more stable. In this way, the glaze paste can be evenly attached to the blank when glazing, without the defects of uneven thickness, flowing glaze or shrinking glaze (glaze shrinks and gathers like dewdrops).

Eliminate the air in the glaze paste: Like clay, the glaze paste will be mixed with a large amount of air after mixing. During the aging process, these tiny air bubbles will slowly merge, float upward, and rupture, resulting in a dense, bubble-free glaze. This directly avoids the appearance of “pinholes” or “bubbles”.

Sufficient hydration and homogenization: Allow all ingredients in the glaze (especially emulsifiers, colorants and other trace ingredients) sufficient time to come into contact with the water and disperse to achieve uniformity at the molecular level. This can effectively prevent the glaze from appearing color spots, color spots or ripples, and ensure the uniformity of color and texture.

Microbiological effects (secondary but beneficial): Sometimes, organic gums (such as CMC) or natural organic matter in glazes are slightly fermented during aging, producing smoother rheological properties and giving the glaze a better feel.

2.2. Specific methods of glaze aging:

The glaze will be ball milled or stirred to the appropriate specific gravity and viscosity, after sieving (such as 200 mesh sieve) poured into the glaze bucket. The glaze bucket is generally used with the lid of the plastic bucket or glaze cylinder. After the glaze paste is poured into the glaze bucket, the lid must be put on to prevent water from evaporating and dust from falling in. Place the glaze bucket in a cool place and let it sit for at least 24 hours, recommended to let it sit for more than 3 days. For some glazes with complex ingredients that tend to settle, aging for 7 days is more effective.

The glaze paste must be re-stirred thoroughly before formal use, as some of the heavy particles (e.g. quartz, feldspar) will settle to the bottom. After mixing the glaze paste, it is best to sieve it again to ensure that there are no lumps or impurities before normal use.

3. Aging of the billet
The term “aging” does not refer to the clay, but rather to the resting and acclimatization of the raw billet (unfired mug) after molding before moving on to the next step in the process.

3.1. Resting after trimming the mugs

The mugs are drawn or grouted, they are usually trimmed. The trimming process cuts and shakes the blank and can create minor internal stresses. After trimming, do not go immediately to the drying stage, but let it sit on the bench for 15-30 minutes. Allow the internal stresses due to machining to be naturally released and equalized. This effectively prevents cracking caused by stresses being released from the weakest point during the initial drying phase.

3.2. “Moisture balance” of the bonded parts

Cracks can easily occur where the mug is bonded to the handle. The main reason for this is the difference in humidity between the two. When gluing the handle to the mug, it is important to make sure that the humidity level of the two parts is the same. How can we achieve the same humidity level between the mug and the handle? Try to make sure that the humidity is the same before you glue them together. If the body of the mug is semi-dry (leather hardness), then the handle should be adjusted to the same moisture level. If the handle is drier, then the finished handle needs to be covered with a damp cloth or placed in an airtight box to be moisturized to achieve as consistent a humidity level as possible between the two.
After the handles and mugs have been bonded, the complete blanks should be left on the bench for half an hour to allow their humidity to blend and unify naturally.

4. Mold Aging
In slurry molding, we usually use plaster molds (for a more detailed explanation, please see “Customized Ceramic Coffee Mugs - Grouting Process Explained”). Plaster molds have their own “age” requirement, but it refers to the recovery period after use. When grouting, plaster molds absorb a lot of water from the blank and become wet. If it is reused immediately, its water-absorbing efficiency will be greatly reduced, resulting in slow molding of the blank, low strength and easy deformation. Therefore, after use, plaster molds must be given sufficient drying time to ensure that their internal moisture has completely evaporated and returned to a dry state before they can be used again. This usually takes 24 hours or more, depending on the ambient humidity and the thickness of the mold.

5. Aging during glazing
There are multiple processes for glazing, the ones we have talked about before are: dip glazing, spray glazing, brush glaze, pouring glazes, swirling glaze and so on. Although the various glazing methods are different, but the plain billet in the glaze before and after the glaze, there is an aging session.
Before glazing: After trimming and drying, raw blanks are very strong, but very brittle, and they absorb moisture from the air (wicking). Therefore, if a rough piece is left for a long time before glazing, its surface will lose its strength due to moisture absorption. At this time, it will be put into the drying room with 40-50 ℃ low temperature drying for a period of time, to drive away the moisture on the surface, so that it will be restored to the best glaze state. This process is the aging before glazing.
After glazing: After the raw blanks are glazed, they need to be left to wait for the glaze to dry. After glazing, place the raw blanks horizontally on a grid drying rack, requiring an ambient temperature of about 25°C and a humidity of about 50%, and dry for 2 hours. Then, the ambient temperature is raised to 40°C, humidity 30%, and circulating fans are activated to accelerate drying for 5 hours. This stage guarantees the perfect combination of glaze and raw biscuit. This process is the aging after glazing.

6. “Aging” during firing
Ceramic mugs in the firing stage, it goes through: heating, holding and cooling. Holding stage, is also the firing of the “aging”. In the holding stage, the raw ceramic mug will slowly evaporate the water, and the quartz crystals will slowly undergo changes. At the same time, in the heat preservation stage, the glaze and the organic matter contained in the paper, at a stable temperature, slow reaction, while eliminating the exhaust gas, complete the glaze and the paper vitrification process. At this stage, the quartz in the clay will undergo a number of changes, mainly β-quartz into α-quartz, its volume expansion of 0.8%. The feldspar in the raw material also melts at this point, and it turns into a glassy phase that fills the pores of the ceramic body. This is the staleness of the firing process for ceramic mugs.

Throughout the entire production process of ceramic mug aging links, their common core is: “time”. Standing time, is an invisible but extremely important production factors in manufacturing. Ceramic factory by consciously giving these materials and semi-finished products the necessary “resting time”, we can use the lowest cost, for the stability of the entire production system and the final quality of the product to buy a most reliable “insurance”.