In-depth analysis of the firing process of ceramic mugs

Xinxiang custom ceramic mug manufacturer, firing is the core part of the production of ceramic mugs, which directly determines the strength, appearance and safety of the mug. Simply put, firing is the transformation of loose clay, glaze and decal paper into a dense ceramic body through high temperature. This process involves complex physical and chemical changes. A little carelessness, ceramic mugs will appear: cracking, deformation, glaze defects, burst flowers and other problems. For ceramic mug factory, the firing stage of the error may cause the kiln scrapped, the whole kiln ceramic mug billet scrapped, the loss of up to tens of thousands of dollars. Therefore, it is important to master the scientific principles and operational details of the firing process.

1. Raw billet and the kiln's scientific matching

In the ceramic mug into the firing stage, the need for adequate preparation. These preparations mainly include: ceramic mug raw blanks, kilns, heat insulation boards and other hardware facilities; engineers, duty technicians, inspectors, etc., but also need to be based on the season, temperature, humidity and other natural factors, to develop a specific firing program such as firing temperature, firing time, lifting time and spreading heat time.

1.1. “Compatibility” of billet and glaze

- Matching coefficients of thermal expansion: the degree of expansion of the billet and glaze when heated must be close. If the coefficient of expansion of the glaze is greater than that of the billet (e.g., if there is too much quartz in the glaze), the glaze will be “cracked” during cooling, resulting in cracks; otherwise, the glaze will flake off.

- Firing temperature matching: high-temperature glaze (1280 ℃) must be matched with high-temperature body (such as high kaolin content of hard clay), low-temperature glaze (800 ℃) can be used in ordinary clay, otherwise the body is not sintered and the glaze has been melted, the cup crumbles when pinched.

1.2. Selection of kiln

- Tunnel kiln: suitable for single-species mass production, but poor temperature control flexibility. The principle is similar to the “assembly line oven”, the use of waste heat to preheat the new cups into the kiln, energy consumption is low.

- Shuttle kiln: suitable for small batch and many varieties, by adjusting the flame distribution of the gas lance (oxidizing flame or reducing flame), special glaze colors can be fired (such as celadon reduction firing).

- Electric kiln: precise temperature control (±5℃), suitable for low-temperature firing of flower paper containing metallic pigments, but the electric wire is easy to wear out under high temperature, and the long-term cost is higher.

These three modes of kilns are chosen according to the specifics of the ceramic mugs to be fired this time. For example, is this time to make samples, small orders, or mass production. Many customers of our factory have also asked why the sample production time is so short, but the real order production time is so long? This is because the choice of kiln is not the same. Tunnel kiln, once into the production of large orders, its production can not be interrupted. One order must be completed before another can be scheduled. So, it seems like the lead time for large shipment production is longer. However, for the ceramic mugs with return orders, we can book the kiln in advance, in which case the production cycle is shortened.

2. Changes of ceramic mugs during the firing process

2.1. Dehydration period (room temperature~300℃) - Ceramic mugs are mainly evaporated cleanly in the preheating period. Raw billets and glazes need to be fired at high temperatures, and the moisture inside the mug is an unsettling factor. It is important to drain the moisture in the preliminary stage to facilitate the stabilization of the shape of the ceramic mug and the melting of the glaze. In the pre-watering stage, the kiln is required to heat up more slowly, exactly how long it takes, but also with the thickness of this ceramic mug, the season and the room temperature to decide. The dehydration stage has a principle of “rather slow, not fast”, rapid heating, which can lead to mug cracking. In the dehydration stage, the treatment of water vapor is also a challenge. Discharge of water vapor can not be allowed to condense again inside the kiln, otherwise, it is easy to cause ceramic mug glaze with “tear”.

2.2. Oxidation period (300 ~ 900 ℃) - ceramic mug in this stage is mainly chemical changes. With low-temperature dehydration, ceramic mug billet began to formally enter the stage of change. This period, the organic matter in the ceramic mug raw billet for carbonization. For example, plant particles such as roots and grass clippings in the clay are burned to produce carbon dioxide. At this time the mug emits black smoke. Sulfides in the raw material are also oxidized. For example, FeS₂ (pyrite) becomes Fe₂O₃ and SO₂ gas, and if not sufficiently oxidized, the glaze will yellow after firing. Oxygen content should be ensured during this period, as the oxygen required for the oxidizing reaction of the raw billet increases. If the oxygen content is insufficient, it will easily lead to the firing of ceramic mugs will appear black spots, smoke and yellowing.

2.3. Bolitization (900°C to the highest temperature) - At this high temperature stage, the clay is officially transformed into ceramic. With the help of high temperature, the quartz in the raw material will undergo some changes, mainly β-quartz becomes α-quartz, and its volume expands by 0.8%; the feldspar in the raw material also melts at 1100℃, and it will turn into a glassy phase to fill the pores of the ceramic body. The glaze also changes at this temperature to a state similar to magma, which evenly covers and fills the surface of the mug as if it were coated with a film. In the high temperature period, the temperature control is very critical, too high or too low temperature can not make the glaze to meet the standard of qualified products. Real-time monitoring of temperature should be carried out during this period. After many ceramic mugs are fired, the glaze feels like snot and is not uniform enough. That's when the temperature is too high during the firing stage.

2.4. Cooling period -- Although the mug has been fired, the cooling period is the last stage, but also the most important one. Otherwise, you may face the “goal kick, the ball flew” embarrassing situation. High-temperature cooling to room temperature can be divided into three stages: fast cooling period (high temperature - 800 ℃), slow cooling period (800-200 ℃), and constant temperature period (200 ℃ - room temperature). The fast cooling period requires rapid cooling, but does not allow the wind to blow directly on the ceramic mug. The rapid cooling is for the solidification of the glaze, and also for the reverse transformation of the quartz, where the α-quartz changes back to β-quartz. Slow cooling period requires a slow cooling speed, and eventually through the constant temperature period temperature drops to 80 ℃ or less, then you can leave the kiln.

3. Precautions for firing ceramic mugs

3.1. ceramic cup billet before putting into the kiln, to mouth down on the heat insulation pad, the cup directly spaced more than 3cm. in the placement of ceramic cups, to check whether the billet has deformation, cracks and other quality problems, quality problems of the cup is not put into the kiln. The reason for placing the mugs with their mouths facing downwards is to avoid dust falling into the mugs in the kiln, and at the same time, it is not easy to deform the mugs during the firing process.

3.2 During the rainy season or when there is a lot of humidity in the air, the kiln should be preheated to remove the moisture, otherwise the mugs will show “tear marks”. In the event of a sudden power failure or gas failure during the firing process, all valves should be closed immediately and the kiln door should not be opened until the gas is restored.

3.3. Cracks in mugs are caused by uneven drying of the billet, residual moisture inside, or too rapid cooling during the cooling period. During the rainy season, the drying time of the billet should be extended, and the cooling time should be extended at the same time.

3.4. When the mouth of the mug is deformed or the body of the mug is deformed, it is caused by the softening of the billet during the high temperature stage due to too rapid heating, which leads to the deformation of the mug body due to gravity. Or because of the uneven thickness of the mouth and body of the mug during the production stage of the billet.

3.5. Pinholes in ceramic mugs. This is caused by the organic matter in the glaze not being burned out. The glaze needs to be filtered through a 200-mesh sieve during the glaze making process. Another reason is that after the glaze is finished and before firing, the glaze is floating. Ceramic mugs need to be dusted with an air gun before entering the kiln to avoid pinholes.

Kiln firing of ceramic mugs is an art, and this technique firing technique was available in ancient China. Historically, earthen kilns were used, along with handmade ceramic products, and this art has been passed down to the present day. Industrialization progressed with various kilns facilitating the mass production of standardized ceramic mugs. In recent years, with the rapid advancement of artificial intelligence and automation technology, the kilns have become more precise and convenient to control. Xinxiang Ceramics Factory has also introduced a number of kilns with the latest technology, automatic billet trimming production lines, automatic glazing production lines and so on. Therefore, we are able to provide customers with the best ceramic coffee mugs with stable quality.

3 production methods and 2 decal methods for ceramic mug decals

Xinxiang custom ceramic mug manufactuer, the process of making ceramic mugs, the clay will become ceramic mugs raw blanks after some series of processes. Ceramic mugs of raw blanks need to be embellished, in the previous article, we introduced the glaze knowledge of ceramic mugs, this article, we talk about ceramic cups of flower paper. In the previous China ceramics introduced ceramic flower paper category is suitable for microwave oven, also introduced, water decal process. Today, we systematically and comprehensively introduce the knowledge of ceramic mugs paper.

1. What is flower paper

Ceramic cup flower paper, is a ceramic mug “makeup” means. It is like a kind of tattoo stickers, through the firing process, the customer's customized pattern, fused to the ceramic mug. Let different ceramic mugs have different pictures, suitable for different people and scenes. So, how is the ceramic flower paper made up? It has 3 layers. The lowest layer is the base layer that holds the pattern. The most commonly used materials for the base layer are kraft paper or water-soluble paper. The base layer is discarded after the application and cannot be involved in the firing. The second layer is the pattern layer, which is made up of pigments. The patterns and colors we choose are reflected in this layer. There are three processes for producing this layer: lithography, screen printing and digital printing. The pattern layer is produced through one of these processes. The top layer is the cover oil layer. The function of this layer is to protect the pattern layer in the center.

2. Flower paper classification

According to the material of the flower paper can be divided into 3 categories: acetal film paper, underglaze flower paper and water transfer decal paper. Often seen is the water transfer paper, today mainly to explain this one. The other two, we will talk about later. According to the firing temperature, ceramic mugs can be divided into: high-temperature paper and low-temperature paper. Purchasers are often asked by the ceramic mug factory is: “this ceramic mug needs high temperature paper or low temperature paper”. According to the temperature distinction between paper, is the most important thing for buyers to understand.

2.1. High-temperature paper firing temperature is 780-850 ℃, high-temperature paper color is light, high solidity. Low temperature floral paper firing temperature is 650-750 ℃, its color is very bright, very bright red and gold are low temperature floral paper. So, what causes them to have different firing temperatures and different vibrant colors after firing? Actually, it's similar to the glazes in our last post. The colors all come from metal oxides. The metal oxides cobalt, manganese, etc. that are used for the colors in the high-temperature flower paper have a high melting point, so they are high-temperature flower paper. On the contrary, low-temperature flower paper with cadmium, selenium and other metal oxides, these oxides are less resistant to high temperatures, but the color is bright, and the firmness of the firing is not as good as high-temperature flower paper.

2.2. High-temperature flower paper and low-temperature flower paper need different adhesives. High-temperature flower paper glue: the glue is natural resin (such as rosin) or high-temperature glue, when fired will be completely burned to ash, leaving no residue. This way the glaze is smooth and will not blister. If the glue is not burned clean, the glaze will have black spots (like burnt rice grains). Glue for low-temperature floral paper: organic resins (such as acrylics) are used, and they burn clean at low temperatures. However, if the temperature is not high enough, the glue residue will stick to the glaze and be sticky to the touch. After firing at low temperature, if you wipe the mug with a wet cloth, the glue residue may whiten (like a tape mark).

3. Flower paper production process

3.1. Lithographic printing (offset printing)

Lithography is the production of patterns on aluminum printing plates, each color corresponds to a plate. When printing, the ink adheres to the raised portion of the printing plate and is transferred to the patterned paper by means of a rubber cylinder. This technique is suitable for mass production and has the lowest cost, which is about $0.1 to $0.3 per sheet of floral paper. If the order quantity exceeds 100,000 pieces, lithography is the most economical choice. However, its disadvantage is that the color is not bright enough, can only print a maximum of 6 colors, and can not show metallic or three-dimensional effect.

3.2. Screen Printing (Screen Printing)

Screen printing needs to make a separate screen plate for each color, through manual color printing layer by layer scraping. For example, when making a gift mug with a gold embossed pattern, workers need to repeatedly scrape 3 to 4 times to increase the thickness of the ink layer. The advantage of this technique is that it can achieve three-dimensional effects (ink layer thickness of up to 0.1 to 0.3 mm) and metallic colors, and is suitable for medium-volume orders (5,000 to 50,000 pieces). However, the color register error is large (about ± 0.5 mm), small characters or fine patterns are easy to blur, and each color needs to be dried, the production cycle is long.

3.3 Digital printing (inkjet printing)

Digital printing eliminates the need for plate making and directly prints the pattern onto the floral paper with ceramic ink, which is cured by ultraviolet light. Digital printing can be done quickly and in rich colors, supporting photo-quality gradient effects. It has the highest flexibility, with orders starting at 50 sheets, but it also has the highest cost ($5 to $8 per sheet) and special colors such as gold need to be filled in later by hand.

3.4. Core differences between the three technologies:

Cost: lithographic < screen < digital (suitable for orders from large to small).

Color effect: digital ＞ screen ＞ lithographic (from gradient to metallic).

Production speed: lithographic suitable for long-term large quantities, digital suitable for urgent small quantities.

4. Decal operation steps

4.1 The first step: pretreatment

Clean the mug: use non-woven cloth dipped in 95% alcohol to wipe the glaze surface to ensure that there is no dust, oil or water marks. If you use paper towels may be residual fluff, wipe with water will lead to poor decal.

Preheat the mugs: leave them in the preheating zone at 40-50°C for 3-5 minutes, especially in winter, to avoid condensation when appliqueing cold mugs which may cause the pattern to shift.

4.2. Step 2: Applique operation

4.2.1. Soaking method (flat mugs):

a. Soak the decal paper in 25℃ water for 8-12 seconds to separate the backing paper from the pattern layer.

b. Slide the pattern onto the surface of the mug, fix the center first, and then use the rubber scraper to scrape from the center to the edge at an angle of 45° to discharge the air bubbles. If the scraping force is too strong, the pattern may be torn, and the residual air bubbles will produce pinholes after firing.

4.2.2. Transfer film method (curved mugs)

a. Cover the pattern paper with transfer film and compact it to make sure there are no air bubbles.

b. Slowly tear off the backing paper and stick the film with pattern to the mug surface, use 60℃ hot air gun to locally heat to assist bonding.

c. Tear off the transfer film evenly, too fast may result in pattern residue.

4.3. Step 3: Drying and Quality Inspection

4.3.1. drying: dry at 55-60 ℃ for 15-20 minutes, touch no wet feeling can be. Too high temperature will lead to glue failure.

4.3.2. QC:

Alignment accuracy: check the pattern splicing at the mug handle, mug mouth, etc., the error needs to be less than 1mm.

Edge checking: use strong light to observe whether the edge is warped or not, and the decal glue needs to be reapplied after discovery.

Bubble treatment: use the tip of a needle to poke bubbles and make up the glue, otherwise it will burst when firing.

4.4 Step 4: treatment before entering the kiln

a. Dust removal: blow the surface of the mugs with an ionic air gun, especially at the inner edge of the mouth of the mugs where dust is likely to accumulate.

b. Stacking protection: invert the mugs on the silicone shelf to avoid handling the pattern.

5. Precautions for the decal process

a. Environmental control: decal workshop needs to be maintained at about 25 ℃, humidity 60%, to avoid deformation of the paper or glue failure.

b. Flower paper preservation: avoid light and flat, expired flower paper (more than 1 year) glue will fail, easy to fall off after sticking.

c. Burning risk: low-temperature flower paper (such as gold) need to strictly control the temperature, more than 750 ℃ may lead to metallic color blackening. The heating stage (300-600℃) needs to be slow (3℃ per minute) to prevent the pattern from cracking.

d. Pattern haloing: Applique when the glaze is not thoroughly dry, need to ensure that the glaze is dry for more than 24 hours after application.

e. Lack of color after firing: check the ink thickness (screen printing needs to be ≥ 20 microns) or kiln temperature is too high.

f. Blackening of the gold edge: the gold-containing flower paper should be fired in the oxidizing flame to avoid contact with smoke.

g. Decals off: Decals need to be put into the kiln within 8 hours, otherwise the glue fails.

Different images of ceramic coffee mugs are derived from ceramic flower paper. The cost and difficulty of making ceramic flower paper is determined by the number of colors, whether there are gradient colors, and special colors such as red, gold and silver. The raw ceramic is the foundation of the mug, and the quality of the glaze and the paper is a direct factor in the aesthetics of the mug. The above information is based on the quality of ceramic flower paper hardware guarantee, ceramic mug flower paper is beautiful, but also by virtue of the ceramic mug factory technical workers operating practices and quality control guarantee. Both hard and soft to ensure that we get our hands on a beautiful ceramic coffee mug.

Instructions for making glaze in ceramic mugs

Xinxiang custom ceramic mug manufacturer, ceramic mug production process, clay through a number of processes (practicing clay, billet molding, drying and billet, plain firing), ceramic mugs will enter the “make-up” stage. Ceramic mug beautification is mainly through the glaze and flower paper to achieve. Custom ceramic coffee mugs, buyers of ceramic factory mentioned one of the main needs is the color and picture. The color of the mug is achieved through the glaze, and the picture of the ceramic mug is done through the flower paper. Today, China ceramic factory first to tell you about the glaze. What is glaze? The color of the cup requested by the customer, China Ceramic Mug Manufacturer is achieved through which process?

1. What is the glaze? How to make it?

1.1 Glaze is like “paint”.

The glaze is a paste-like liquid before it is put into the kiln to be fired. Ceramic mugs coated with glaze, put into the kiln firing, it becomes a smooth layer of the surface of the mug “glass layer”. The purpose of the glaze is waterproof, beautiful and durable.

1.2 How is the glaze made?

a. Matching raw materials: according to the color requirements of the custom ceramic coffee mug, ceramic factory will find out the corresponding color value. We prepare the raw materials (including: quartz stone, feldspar, kaolin and other materials) according to the formula.

b. Powdering: The ceramic factory pours the mixed raw materials into a ball mill (a barrel-shaped machine with many small stone balls inside). Add water and grind into a fine powder slurry (like soybean milk, grind until there is no graininess to the touch).

c. Sieve: Use a fine mesh to sieve out large particles to ensure that the glaze paste is fine.

d. adjust the concentration: in accordance with the recipe, add water and adjust to a little thicker than milk state (too thin to hang the mug, too thick will crack).

e. Storage glaze paste: loaded into a vat, regular stirring to prevent precipitation.

1.3. Glaze storage precautions

a. Anti-drying: the bucket holding glaze paste should be sealed, otherwise the surface caking (like soybean milk put for a long time peeling).

b. Anti-freezing: glaze paste can't be put outside in winter, glaze paste will be stratified after freezing.

c. Shelf life: glaze paste in sealed and room temperature, do not store more than 3 months, otherwise it will deteriorate (glaze paste will smell or hard lumps).

d. Safety: glazes containing lead and cadmium should be labeled separately.

2. the role of each component in the glaze

2.1. quartz (sand): glaze raw materials account for the most quartz, can account for more than half. Quartz is the glaze “skeleton”, it is in the glaze after firing, can make the glaze hard.

2.2 Feldspar: it is a natural “accelerant”, it allows the glaze to melt at low temperatures, its main role is to reduce the melting point of the glaze.

2.3. Kaolin: It acts as a binder, which allows the glaze to stick firmly to the mug.

2.4. Metal Oxides: The color of the glaze is determined by the metal oxides. The color of the glaze varies according to the amount of metal oxides added. For example, if iron oxides are added to the glaze, the glaze takes on a yellowish-brown color; if cobalt is added, the glaze turns blue; if copper is added, the glaze turns green.

2.5. opalizing agents: for example, tin dioxide, which whitens and makes the glaze opaque, giving it a white color.

3. The difference between high temperature glaze and low temperature glaze

Customized ceramic coffee mugs, ceramic factory will habitually ask buyers: “need to be made into high temperature glaze ceramic cups, or made into low temperature glaze ceramic cups?” Many buyers for high temperature glaze and low temperature glaze is not clear, the difference between the two and the advantages and disadvantages are not understood. Then, China ceramic factory to make both clear.

3.1. High-temperature glaze, is the firing stage, which requires a higher temperature (1280 ℃ or more) for firing. It requires a higher temperature, then the more energy consumed in the firing process, so the cost of production is also high. This high-temperature glaze is more wear-resistant and environmentally friendly (it does not contain lead or chromium). Ceramic mugs with high temperature glaze last longer and are safer. However, high-temperature glazes cause many colors to be less vibrant than low-temperature glazes because of the high temperature.

3.2 Low-temperature glaze refers to the firing stage, only need a relatively low temperature (about 800 ℃) can be made. Low-temperature glazes require low temperatures, so less energy is needed in the firing process, and the production costs are lower. This low-temperature glaze guarantees the vividness of the colors and takes less time to produce. However, this kind of low temperature glaze has poor abrasion resistance and is more easily scratched.

4. How to judge the quality of glaze

4.1. After the sample coated with glaze in the test firing, through the test finished glaze, to judge the quality of the glaze. Sample glaze surface if smooth, no cracks, no pinholes, then the quality of this batch of glaze paste is qualified. On the contrary, this batch of glaze paste is unqualified.

4.2. by knocking the sample, by virtue of the sound to determine the quality of the glaze. Tap the sample to listen to the sound, if the sound is crisp, then you can judge the adhesion of the glaze is qualified. If the sound is muffled, then the adhesion of the glaze is not qualified.

4.3. Immerse the sample in an acid solution for 24 hours. After immersion, watch for changes in the glaze. If there is no change, the glaze paste is qualified, and vice versa.

5. Glaze precautions

5.1. formula: the same color, different factories, the production of ceramic mugs, the color is different. Mainly is reflected in different formulas, formulas and personnel is a qualified, stable ceramic mug factory, the cornerstone of survival.

5.2. Inspection: After the glaze paste production is completed, it should be regularly stirred and inspected. Prevent the glaze paste from deteriorating and settling.

5.3. Firing: high-quality finished ceramic mugs, not only rely on good quality glaze paste, in the firing, but also need to strictly control the firing process. Otherwise, the glaze will not be bright; low temperature glaze over temperature will flow glaze.

What is the plain firing process for raw ceramic mugs?

Xinxiang Ceramic Mug Manufacturer,  in the process of making ceramic mugs, raw materials made of clay after molding, drying, billeting and other processes, before the billet glaze. Some of the raw ceramic mugs need “plain firing” process, the rest is directly glazed. So, what is the plain firing in the end? What kind of situation needs to burn process? In fact, vegetarian firing is a kind of early firing, it has an important role in improving the quality of ceramic mugs, of course, this process will also increase the ceramic cup in the production of links in the cost and time.

1. What is vegetarian firing?

Vegetarian firing is a ceramic mug billet in the dry, repair billet, before the formal glaze firing, a low-temperature firing (usually 700-900 ℃), the mud “half-burned”. Burned blanks as crisp and hard as a cookie, but not yet turned into porcelain.

2. What needs to be fired?

2.1. 4 kinds of situations that need to be fired:

2.1.1. to do complex decoration: such as hand-painted patterns, underglaze color, underglaze appliqué (plain firing after the billet water absorption, underglaze color is easy to color without losing color).

2.1.2. the billet is too thin or complex shape: such as thin tire mug, shaped mugs (high strength after plain firing, not easy to break when handling and glazing).

2.1.3. with special glaze: such as matte glaze (matte glaze liquidity is poor, direct glaze on the blank is easy due to uneven absorption of water on the blank resulting in mottled glaze. Plain firing after billet water absorption stabilization, glaze distribution is more uniform.) The crystallized glaze (crystallized glaze firing temperature is high 1320 ℃, and need to keep warm for a long time. After firing, the body is strong enough to withstand the thermal stress of glaze firing, avoiding cracking.) .

2.1.4. Export or high-end products: Plain firing can expose the defects (such as dark cracks) of the blank body in advance and reduce the final firing scrap rate.

2.2. There are 3 kinds of cases that do not need to be burnt:

2.2.1. Ordinary mugs with large quantity and low price: direct raw glaze, saving time and money.

2.2.2. high strength clay: such as the addition of clinker (crushed porcelain powder) of coarse pottery mug, itself is not fragile. 3.

2.2.3. glaze is simple: such as monochrome glaze, direct spray glaze can also be attached.

3. The advantages and disadvantages of plain firing

3.1. The advantages of raw blanks after plain firing are:

3.1.1. the billet becomes hard, the handling is not fragile.

3.1.2. more uniform glaze, bright color.

c. early detection of cracking, deformation defects.

3.2. Disadvantages are:

3.2.1. firing more than once, time-consuming and gas-consuming.

3.2.2. vegetarian firing occupies kiln space, lower output.

3.2.3. Improper operation may overfire (glaze can't stick after porcelainizing the blank).

4. Vegetarian firing operation steps

4.1. Load the kiln

- How to set up: mugs face down, at least 2 finger width apart (to prevent sticking).

- Pad what: the bottom of the mug sprinkled with a layer of alumina powder or pad refractory sand (to prevent sticking to the kiln board).

4.2. Firing temperature

- Ordinary clay: Fired to 800-850 ℃ (the body becomes light red, knocking sound like tile).

- High-white porcelain clay: fired to 900-950 ℃ (the body of the white, knocking sound like tiles).

4.3. How long to burn?

- Warming up: from room temperature to the target temperature in about 5-6 hours (150℃ per hour).

- Holding time: 30 minutes after reaching the temperature (to let the heat penetrate into the center of the billet). Cooling: Turn off the kiln to cool down naturally.

- Cooling: Turn off the kiln and let it cool down naturally to below 100℃ before opening the door (rapid cooling will cause cracks!). Cooling: Turn off the kiln and let it cool down naturally to below 100℃ before opening the door (rapid cooling will crack!)

5. Precautions

5.1. Inaccurate temperature will turn over:

- Must use thermocouples to measure the temperature, can not rely on experience to see the color of the flame!

- Temperature is too low (<700 ℃): billet strength is not enough, a touch will be broken.

- Temperature is too high (> 950 ℃): body porcelain, glaze can not hang. 2.

5.2. Check after firing:

- Drip test: drop a drop of water at the bottom of the mug, within 5 seconds to seep in is considered qualified (water absorption rate of 12% -15%).

- Failed products: cracked sound muffled, no water seepage directly scrapped. 3.

5.3. Storage of plain billet:

- Put in a dry box (humidity <40%), otherwise the glaze will blister after absorbing moisture.

In summary, plain firing is a ceramic mug in the production process to improve the quality of the process. It can improve the quality of the raw ceramic mugs, in the later glazing, hand-painting, paste underglaze flower paper and other processes, is essential. Simply put, high-end ceramic mugs often need this plain firing process. The ceramic mugs made in this way are more environmentally friendly and exquisite. Of course, the vegetal firing process will increase the cost and time of production, which means that when customizing ceramic mugs, the price of such ceramic mugs is also higher. China ceramic mug factory thinks this kind of ceramic mugs after the plain firing process is more suitable for coffee shops, branded gifts and so on, which have higher requirements for quality.

Drying and trimming process of ceramic mug clay blanks

Xin xiang custom ceramic mug factory, the production of ceramic coffee mugs in the selection of good raw materials, raw materials will be mixed and processed, after dewatering and practicing clay. Then came to the introduction of the “billet molding” link. At this time, the prototype of the ceramic mug was formed, but not perfect, how to make the mud blank more exquisite? Then, drying and trimming the two links, is the next important step. Ceramic mugs of the role of the drying process is: to reduce the moisture in the mud, in order to prevent the firing process in the ceramic mugs cracked; repair is to make the ceramic mug size, weight and other parameters in line with customer demand, and will be ceramic mugs imperfect place for “beautification”. Therefore, these two links are very important, then how to operate, and what are the precautions? Please listen to my slow talk:

1. Drying operation guide

Purpose: to remove moisture from the body of the blank, to prevent the kiln firing burst.

1.1. Preparation before drying

- Placement of the blanks:

- Place the wet blanks of ceramic mugs (moisture content of 18%-22%) on a hollowed-out plastic tray, with the mouth of the mug facing downwards, to avoid water accumulation inside the mug.

- The blanks should be spaced ≥ 5cm apart to ensure even air circulation.

- Environmental control:

- Natural shade drying: choose a ventilated workshop without direct sunlight, humidity 60%-70% (can be monitored by hanging hygrometer).

- Drying room: preheat to 30℃, humidity set at 50% (assisted by industrial dehumidifier).

1.2 Practical operation of drying process

a. Initial drying (0-12 hours):

- Focus on removing surface moisture and observe every hour whether the billet is deformed.

- Natural drying: Close some of the vents at night to prevent a sudden drop in temperature.

- Drying room: Increase the temperature by 2℃ every hour to 40℃ and keep it stable.

b. Intermediate drying (12-24 hours):

- Turning the blanks: Place the mugs on their sides to avoid one-sided shrinkage too fast resulting in crooked mugs.

- Check the seam line: if the joint between the handle and the mug is white (difference in moisture content), gently rub the transition area with a damp sponge.

c. Final drying (24-48 hours):

- Moisture content test:

- Feeling method: touch the bottom of the cup without wet and cold feeling, fingertip flick cup wall issued a crisp “ding” sound.

- Instrumentation: infrared moisture meter detection (sampling the center of the bottom of the mug, reading ≤ 2%).

- Correction of deformation: If the mouth of the mug is slightly elliptical, it can be adjusted with the palm of the hand while the blank is slightly wet (moisture content of 5%).

1.3. Precautions

- Anti-cracking:

- Avoid direct fan blowing on the blank, give priority to natural convection.

- Thick parts of the mug (such as the root of the handle) can be wrapped with a wet cloth to slow down the drying process.

Anti-pollution: drying room filter is cleaned weekly to prevent dust from adhering to the blank.

2. Operation Guidelines for Trimming

Purpose: trimming the shape of the blank, remove burrs and seam lines.

2.1. Tool Preparation

- Wet trimming tools:

- Stainless steel scraper (blade width 10mm, thickness 0.5mm) - to cut off the parting line.

- Natural sponge (aperture 1-2mm) - to wet the joints to prevent chipping.

- Dry repair tools:

- Carbon steel trimming knife (curved tip) - trimming the curvature of the mug.

- Sandpaper (120 mesh coarse grinding, 400 mesh fine grinding) - handle polishing.

- Vacuum cleaner - real-time dust cleanup.

2.2 Wet dressing procedure (moisture content 8-12%)

a. Remove the mold line:

- Left hand fixed mug, right hand holding scraper and the wall of the cup at an angle of 30 °, along the mold line lightly scraping, strength to “see the mud flying out, not hurt the blank” prevail.

- Key point: the scraping direction is the same as the opening and closing direction of the mold (usually vertical direction).

b. Handle joints:

- Wet the joints with a sponge dipped in water, and cut the excess clay with a spatula at an angle of 45°, so as to form a smooth transition (the difference in thickness is ≤0.3mm). c. Flattening the mouth of the cup.

c. Flatten the mouth of the mug:

- Invert the mouth of the mug on the rotating disk, scraper horizontal fit the edge of the mug, rotate at a constant speed to remove burrs.

2.3 Dry repair operation steps (moisture content ≤ 2%)

a. Finishing the mouth of the mug:

- Use 400 mesh sandpaper wrapped in wood, along the inner wall of the mug clockwise sanding, to eliminate the “knife cutting edges.

- Detection standard: finger scratching the mouth of the mug without scratching, no reflective burrs under the light.

b. Foot trimming:

- Cut the bottom of the mug vertically with a carving knife to a depth of 2-3mm, forming a 45° chamfer (to prevent sticking to the kiln plate after firing).

- Sandpaper the edges of the foot until rounded (roughness Ra ≤ 6.3μm).

c. Handle polishing:

- Use toothbrush dipped in water to remove dust from the grooves of the handles, and sandpaper with 120 grit sandpaper along the grain until there is no graininess.

2.4 Quality control and problem handling

- Repair common defects:

- Fine cracks: Fill with brush dipped in mud, and partially sand after drying.

- Uneven seams: fill with mud (mud:water=3:1), re-scrape flat.

- Full inspection standard:

- Dimensional tolerance: tolerance of mug diameter ≤±0.8mm (10% sampling with vernier calipers).

- Weight deviation: weight difference of the same batch of mugs ≤ 3% (weighed by electronic scale).

3. Cleaning and quality inspection

Purpose: to ensure that the blanks are dust-free and free of defects, in preparation for glazing.

3.1. Dust removal:

- Use compressed air to blow the surface floating dust, or use a soft brush to sweep lightly.

3.2. Water immersion test:

- Immerse the blank in water for 2-3 seconds and observe whether there are bubbles (if there are, there are dark cracks).

3.3. Full inspection standard:

- Appearance: no cracks, bubbles, deformation;

- Dimension: error of mug diameter and height ≤±1.5%;

- Strength: no collapse of the mug wall when pressed by fingers.

3.4. Points of Attention:

- Non-conforming products need to be crushed and returned to the clay system (add proportion ≤ 5%);

- After the quality control of the blanks need to be glazed within 24 hours to avoid moisture absorption.

The drying process of ceramic mugs is a key link that affects the yield. Some ceramic mugs will blow up when pouring hot coffee, besides the raw material problem, the biggest problem is the drying process. The manual trimming link tests the technician's responsibility and proficiency. China Ceramic Mug Factory has introduced electronic equipment, including electronically controlled drying room and automatic trimming assembly line (for details, please check the video released by our factory). The drying process is strictly controlled by electronic equipment and the efficiency and consistency of the trimming process has been improved. If you need custom ceramic mugs, then please find a more professional, attentive and advanced ceramic factory.

Ceramic mug raw materials - clay preparation process

Xin xiang ceramic mug manufacturer, in the previous article, China Ceramic Mug Manufacturers introduced, the three basic raw materials for ceramic mugs. The three basic raw materials after processing, became the clay material for making ceramic mugs. Mud preparation is the basic link of ceramic production, directly affecting the stability of subsequent molding, drying and firing. For the compression molding of mugs, the clay's: plasticity, moisture content, particle uniformity and other indicators are particularly critical. This has gone through what process, different links in the quality control for the later ceramic mug quality has what impact? Well, I would like to know more about customized ceramic mug knowledge buyers, one by one to answer.

1, the composition and function of ceramic clay

a. Kaolin, bentonite, ball clay

Their main role is: to provide plasticity, so that the clay is easy to mold and maintain the shape.

b. Quartz sand, calcined kaolin

Their main functions are: to reduce drying shrinkage, enhance the strength of the blank and prevent deformation.

c.Feldspar, nepheline orthoclase

Their main role is: to reduce the firing temperature (1200-1300 ℃), promote the formation of glass phase, enhance the degree of porcelain.

d. CMC (carboxymethyl cellulose), sodium humate

Their main role is: to regulate the liquidity of the mud, enhance the strength of wet blanks, to prevent cracking.

2. Key indicators of clay performance

Plasticity: the ability of clay to deform and not crack under external force, determined by the proportion of plastic raw materials and particle fineness.

Water content: 18%-22% water content for billet molding (30%-35% for slurry molding).

Particle gradation: coarse and fine particles are reasonably matched to reduce porosity (ideal particle size: <0.1mm accounts for 60%-70%).

Drying shrinkage: generally controlled at 5% -8%, too high easily lead to cracking.

3. Formulation of clay

Kaolin (45%), ball clay (25%), quartz (15%), feldspar (12%), CMC (1.5%), water (adjusted to the total weight of 22%)

4.Process of making mud

Firstly, pre-treat the raw materials, then mix the ingredients, then sieve and remove the iron, and finally dewater the mud.

4.1 Pre-treatment of raw materials

a. Coarse crushing:

Large raw materials (such as quartzite, kaolin) with jaw crusher crushed to particle size ≤ 5mm.

b. Removal of impurities:

Magnetic separator to remove iron chips (to avoid black spots after firing);

Water washing to remove sediment and organic matter (soaked and precipitated to remove impurities).

c.Aging:

Mixed raw materials are stacked in a shady and humid environment, covered with wet cloth aging for 3-7 days to promote uniform penetration of moisture.

4.2. Ingredients and mixing

a. Weighing and proportioning: weigh each raw material accurately according to the formula (error ± 1%), for example: kaolin 45kg + ball clay 25kg + quartz 15kg + feldspar 12kg + CMC 1.5kg + water (adjusted to 22% of the total weight)

b. Dry mixing: put the raw materials into the wheel mill, low speed (20-30rpm) mixing 20-30 minutes until the color is uniform.

c.Wet mixing: add water and transfer to mixing tank, mix at high speed for 1-2 hours to form a fluid slurry without lumps.

4.3. Sieving and iron removal

a. Sieving: pour the slurry into 80-120 mesh vibrating screen to remove coarse particles that are not crushed (sieve residue ≤ 0.5%).

b. Iron removal: the slurry flows through the electromagnetic iron remover (magnetic field strength ≥ 1.2T), circulating 2-3 times to no iron residue.

4.4 Dewatering and mud training

a. Dewatering:

Mud is pumped into filter press, pressurized to 0.8-1MPa, and pressed into mud cake with 25%-30% water content.

Or use vacuum extruder to dewater directly to the target water content (18%-22%).

b. Clay practicing:

Put the mud into the vacuum mud trainer and repeatedly squeeze 3-4 times to expel air bubbles (vacuum degree ≥ -0.095MPa).

After practicing the mud cut into 10-15cm diameter cylindrical pieces of mud, sealed and kept in reserve.

In summary, this is the whole process of making clay for ceramic mugs. In this process, the quality of raw materials, the control of each link, directly constitute the quality of ceramic mug. For example: some ceramic mugs have black spots, this is the clay “in addition to iron” link, quality control is not enough reason. Also, ceramic mug cracks, many quality problems, from the source. China Ceramic Mug Manufacturer, has been strictly control the raw materials and production of each link, to provide high quality ceramic mug.

Ceramic mug molding production process details

Xin xiang custom ceramic mug manufacturer, once the clay is prepared for the custom production process of ceramic mugs, the molding and shaping process will take place. The so-called molding forming is also the shape of the ceramic mug that we can see. Including: the shape of the ceramic mug, size, thickness, with or without a handle and mug lid. Xinxiang Ceramic Mug Manufacturer in the pressure blank forming (molding) of the link, from the technical details, equipment selection, operating procedures to quality control, for your detailed analysis of the core points of this process:

1, the depth of the analysis of the compression molding process

1.1 The principle of the process

Compression molding through mechanical pressure, the plasticity of the clay in the mold pressing molding. Pressing molding is divided into: single-sided press blank (only the upper mold pressure) and double-sided press blank (upper and lower mold pressure at the same time). Mug because of the simple structure (mug + handle), single-sided press blanks and double-sided press blanks, are in use. The old equipment is mostly used for single-sided pressing, with the update of the equipment, Xinxiang Ceramic Mug Manufacturer has also introduced 3 sets of new equipment for double-sided pressing. Double-sided press blanking can mold the handle and mug at one time, avoiding later bonding.

1.2. Core equipment and molds

a. Equipment selection:

Hydraulic press: stable pressure (common pressure range 50-200 tons), suitable for complex molds, adjustable holding time.

Mechanical press: higher efficiency (10-15 stampings per minute), but lower pressure control accuracy, suitable for simple molding.

Automated assembly line: integrating feeding→pressing blanks→demolding→conveyor belt collecting blanks, suitable for mass production with daily output of more than 10,000 pieces.

b.Mold design:

Material:

Metal mold (steel/aluminum alloy): wear-resistant, long life (up to 100,000 times or more), suitable for large quantities.

Resin reinforced plaster mold: low cost, but short life (about 5000 times), suitable for small batch trial production.

Structure:

Position of parting line: need to be designed in the hidden place on the side of the mug to avoid affecting the appearance.

Air venting slots: tiny air holes are set inside the mold to prevent air from stagnating and causing bubbles during pressing.

Slope of mold release: 1-3° slope should be designed on the inner wall of the mouth of the mug, which is easy to release the mold without sticking.

1.3 Clay Requirements

Composition: kaolin (40%-50%), ball clay (20%-30%), quartz (15%), feldspar (10%), plus a small amount of carboxymethyl cellulose (CMC) to enhance plasticity.

Moisture content: 18%-22% (too dry, easy to crack, too wet, sticky mold).

Pre-treatment: the clay should be processed by vacuum mud machine to eliminate air bubbles and enhance the density.

2、Pressing billet molding operation process

2.1 Clay preparation

The clay block is cut into standardized size (such as 100mm diameter × 60mm high cylinder), the weight error ± 2g or less.

2.2. Press molding

Steps:

a. Put the clay block into the lower mold manually or by mechanical arm;

b. The upper mold is lowered and pressurized (pressure 5-10MPa, holding pressure 2-5 seconds);

c. Remove the blank by suction cup or robot after demolding.

Key parameters:

Pressure: the thinner the wall of the mug, the higher the required pressure (e.g. 8-10MPa for 3mm thin wall);

Holding time: adjusted according to the moisture content of the clay (high moisture content can be shortened to 2 seconds).

2.3. Blank finishing

Wet finishing: immediately after removing the mold, wipe the seam lines with a sponge and smooth the edges of the mugs.

Dry finishing: when the billet is half dry (8%-12% water content), trim the foot with a metal knife and polish the handle joints.

3、Advantages and limitations of billet molding

Advantages

3.1. High efficiency: a single hydraulic press can produce 300-500 blanks per hour (up to 1000+ for automated lines).

3.2. High consistency: mold forming ensures dimensional error of ≤1mm, suitable for standardized brand orders.

3.3. Low breakage rate: high density of pressed blanks, stable drying and firing shrinkage (8%-12%), low risk of cracking.

3.4. Complex structure molded in one piece: no need to bond the mug + handle, improved strength.

Disadvantages and Solutions

3.5 High mold cost:

- Solution: Initially, the mold can be sent out for processing, but the purchase price of abrasives is high. Small orders, if you need to develop a separate mold, the price of a single product needs to share the cost of molds, so the price is high, on the contrary, the price is stable.

3.6 Restricted modeling:

- It is not possible to make deep cavities (e.g. fine and high mugs) or openwork patterns. Complex ceramic mugs require another process: grouting (see: Customized Ceramic Coffee Mugs - Grouting Process Explained).

4. Critical quality control points before kilning

4.1. Moisture content testing:

- Use infrared moisture meter to make sure the moisture content of billet is ≤2% before entering into kiln to prevent bursting.

4.2. billet strength test:

- Sampling blanks from a height of 10cm drop to the sponge mat, no cracking is qualified.

4.3. Dimension sampling:

- Focus on measuring the mug diameter, height, handle angle (the error should be in line with the customer's drawings).

Compression molding is one of the core technology of ceramic mug production, this technical link directly affects the quality of ceramic mugs. Ceramic mug factory only to ensure the quality of each link, in order to ultimately produce high-quality, stable ceramic mugs.