Ceramic tile glaze construction is the core process with the highest defect occurrence rate and the greatest impact on the quality of finished products in the production of building ceramics. The glaze formula determines the upper limit of the glaze surface, while the glaze application process, glaze slurry rheological control, body state, equipment parameters, and environmental temperature and humidity determine the final product qualification rate. The vast majority of problems such as pinholes, bubbles, sagging, glaze threads, shrinking glaze, orange peel, uneven thickness, color difference, whitening and loss of luster on glazed surfaces are not caused by formula issues, but by inadequate control of the entire glaze application process.
This article systematically refines the five mainstream glazing processes, construction prerequisites, glaze slurry standardization control, equipment operation SOP, process quality control points, post glazing maintenance, firing linkage control, seasonal working condition fine-tuning, high-frequency defect traceability and cure solutions in the ceramic tile industry, fully adapting to the mass production and implementation of floor tiles, wall tiles, rock slabs, large slabs, antique tiles, and sanitary ware ceramics.
1、 Principles, parameter standards, and operating procedures of the five mainstream glazing processes for ceramic tiles
The glaze application process for ceramic tile mass production can be divided into five major systems: pouring glaze, automatic spraying glaze, throwing glaze, roller printing glaze application, and immersion glaze. Different processes have completely different requirements for glaze slurry solid content, viscosity, thixotropy, particle fineness, defoaming state, and yield value, and cannot use universal parameters.
1. Glazing process
Process principle: The glaze slurry is circulated by the glaze pump to the glaze sprayer, and a continuous, uniform, and uninterrupted vertical glaze curtain is formed through the overflow slit. The brick body passes through the glaze curtain horizontally at a constant speed and relies on gravity to infiltrate and adsorb to form a film. It is currently the standard glaze application process with the highest flatness, the most uniform glaze layer, and the highest production efficiency. Suitable for applying gloss glaze, matte glaze, soft polishing glaze, ordinary surface glaze, base glaze, and full system flat ceramic tile glaze.
Standard process parameters (universal red line for mass production)
Glaze slurry solid content: 58% -68% (heavy zirconium white glaze upper limit 68%, matte fine glaze 58% -62%)
Apply 4 cups viscosity: 28-40s (slightly adjusted for low in summer and high in winter)
Glaze slurry pH value: 8.0-9.0, weakly alkaline stable range
Screen filtration: 100 – 120 mesh full process filtration, no coarse particles, no agglomeration gel
ü Conveyor speed: Matching according to the thickness of the glaze layer, conventional mass production is 8-18m/min
Glaze tank circulation status: 24-hour uninterrupted low-speed circulation to prevent static settling
Key points of standardized operation
The core of glazing is “stable glaze curtain, no bubbles, no interruption, and constant flow rate”. Before starting up, it is necessary to cycle and defoam for 5-10 minutes in advance, observe that the glaze curtain is transparent and uniform, without stripes or jagged edges before passing through the brick; During the production process, it is strictly prohibited to significantly adjust the glaze slurry or rapidly adjust the pump frequency to avoid batch thickness differences caused by fluctuations in the glaze curtain; Clean the narrow slit of the glaze applicator daily to prevent the accumulation of dry glaze residue, which can cause wire drawing and glaze streaks; Accumulation of sediment is strictly prohibited at the bottom of the glaze storage tank, and slag should be discharged once per shift.
Process adaptation rheological requirements: It must have excellent thixotropy, smooth high shear flow, sufficient low shear yield, no sagging when passing through bricks, and no sagging when stopping the machine. It is preferred to use a composite system of bentonite+trace CMC or magnesium aluminum silicate.
2. Automatic glaze spraying process
Process principle: Using compressed air to atomize glaze slurry into fine droplets at high speed, evenly spraying and adsorbing on the surface of the body, it can achieve uniform glazing at multiple angles, curved surfaces, and concave convex textures, making up for the shortcomings of glazing that is only suitable for flat surfaces. It is divided into reciprocating machine glaze spraying, multi gun array glaze spraying, and robotic arm intelligent glaze spraying.
Standard process parameters
Glaze slurry solid content: 50% -60% (lower than glaze coating, ensuring fine atomization)
Apply 4 cups of viscosity: 18-30s, if the viscosity is too high, it will block the gun and cause coarse atomization; Low glaze and exposed base
Working pressure: 0.25-0.4MPa, stable pressure without fluctuations
Spray gun distance from the blank: 20-35cm for vertical spraying
Filter standard: 120 mesh fine filtration, absolutely eliminating coarse particles
Core Operating Standards
Adhere to the principle of “multiple thin spraying and stacked spraying forming”, and prohibit one thick spraying, as thick spraying can easily cause glaze layer accumulation, sagging, and cracking after drying; The spray gun travels at a uniform speed, without any pauses or dead corners; Compressed air must be dry and free of oil and water. Mixing oil and water into glaze can directly cause batch shrinkage, needle marks, and rough surfaces; Clean the nozzle, pipeline, and stabilizing tank daily to prevent particle defects caused by dry glaze residue falling off.
3. Glazing process
Process principle: Relying on the centrifugal force of high-speed rotating disc, the glaze slurry is thrown out to form uniformly sized random textures such as dots, mist, and flakes. The main focus is on the antique natural texture and random mottled texture, which is the core decorative process of antique bricks.
Parameters and Control Points
The rotational speed of the disc determines the size of the spots, while the flow rate of the glaze determines the degree of density; This process requires extremely high stability of glaze slurry suspension. Once heavy pigments and particles settle, uneven size spots, local white spaces, and chaotic texture defects may occur. Adapt to the composite salt resistant suspension system of concave convex soil, ensuring uniform suspension of particles throughout the process without layering. It is strictly prohibited to have significant fluctuations in the viscosity of glaze slurry during production, otherwise there will be significant color and texture differences between batches.
4. Roller/screen printing glaze application
Process principle: The high thixotropic glaze slurry is transferred to the brick surface through rollers or mesh holes, forming clear lines, textures, and patterns, which belongs to the fine decorative glazing process.
Core control focus
Printed glaze must have high yield value, low flow, and no bleeding. Insufficient thixotropy and low yield value of glaze slurry can result in texture blurring, edge sticking, bold lines, and blurry patterns; Excessive viscosity can cause clogging, missing flowers, and broken lines. Production needs to strictly control the proportion of inorganic suspension agents, improve static structural strength, and reduce the amount of cellulose used to ensure clear patterns, sharp edges, and consistent batches.
5. Glazing process
Process principle: Immerse the preheated body as a whole into the glaze slurry, rely on the capillary adsorption of the body to hang the glaze, and control the flow to form after removal. The advantage is that the glaze layer is evenly wrapped and has no dead corners; The disadvantage is that the thickness is difficult to control and the bottom edge is prone to glaze accumulation.
Operating Specifications
The soaking time must be standardized and unified, as inconsistent lengths can lead to differences in thickness and color difference; Maintain consistent flow control time after glazing to prevent the accumulation and hanging of bottom glaze slurry; The glaze slurry must be stirred throughout the entire process to prevent uneven thickness between the upper and lower layers caused by thin surface and thick bottom.
2、 Standardized state control of the body before glazing
80% of glaze defects are caused by substandard body condition, rather than glaze slurry issues. Before applying glaze, it is necessary to strictly control the four major indicators of moisture content, body temperature, surface cleanliness, and body strength.
1. Moisture content of the billet
Standard range: 0.5% -2.0%
Excessive moisture content: There is residual free water inside the body, and after glazing, the glaze layer seals off the water vapor. When fired at high temperatures, the water vapor expands and overflows, causing a large number of pinholes, bubbles, glaze pits, and glaze bubbles; Excessive moisture content can lead to thick adhesion, slow drying, and severe sagging of the glaze layer.
Low moisture content: The body is excessively dry, the capillary pores are overdrawn, the amount of glaze is insufficient, the glaze layer is thin, the base is exposed, the covering power is poor, the color is light, and the gloss is uneven. At the same time, the body absorbs the slurry too quickly, and the glaze layer is instantly dehydrated and cracked.
2. Surface temperature of the billet
Standard range: 40 ℃ -70 ℃
High temperature: The glaze slurry rapidly dehydrates and forms a crust upon contact, resulting in shrinkage, rolling, cracking of the glaze layer, and orange peel. The glaze slurry cannot spread and level normally.
Low temperature: The drying speed of the glaze slurry is extremely slow, the fluidity of the glaze layer is too high, and it is easy to sag, accumulate glaze on the bottom edge, and have thick and thin edges. After drying, the glaze layer becomes soft and powdery.
3. Surface cleanliness of the blank
Dust on the surface of the blank, kiln dust, oil stains from mold release agents, fingerprints, and static dust accumulation are the top causes of shrinkage, pinhole, glaze layer peeling, and local loss of gloss. Before applying glaze, it is necessary to go through the processes of blowing dust, removing dust, and eliminating static electricity to ensure that the surface of the blank is clean, free of impurities, and grease.
4. Body strength and green quality
Insufficient strength, falling powder, slag, and dark cracking of the green body, as well as knocking and dropping powder during the glazing process, can cause contamination of the glaze slurry, particle defects, and pinhole defects when dropped into the glaze groove; After glazing, the cracks in the dark cracked body absorb water and expand, and after firing, they exhibit explosive cracking, glaze cracking, and line cracking.
3、 Standardization preparation and control rules for glaze slurry before online production
Glaze slurry control strictly prohibits “only looking at viscosity, not looking at solid content, not looking at rheology, not looking at pH”. The complete control dimensions include: solid content, viscosity pH、 Eight indicators: thixotropic state, defoaming state, fineness, suspension stability, and filtration state.
1. Mixing and circulation control
Continuous low-speed mixing and circulating flow throughout the process, high-speed violent mixing is prohibited. High speed stirring will draw in a large amount of air, forming tiny bubbles. After glaze application, the bubbles will be sealed inside the glaze layer, and when fired, they will burst and form pinholes and pockmarks. If the machine is stopped and left to stand for more than 30 minutes, it must be thoroughly stirred again, the bottom must be turned over, and the soft sediment must be thoroughly dispersed before it can be put online.
2. Filtering control standards
Conventional glaze with 100 mesh filtration, high-quality transparent glaze and ultra white glaze with 120 mesh fine filtration; Regularly inspect the screen mesh for damage, leaks, and slag accumulation during each shift; The newly formulated glaze slurry must be double filtered to eliminate fish eye suspension agent particles, coarse melt particles, and external impurities.
3. Linkage control of solid content, viscosity, and temperature
The viscosity of glaze slurry varies greatly with temperature: in winter, the viscosity is higher at low temperatures and the rheological properties are poor; In summer, the viscosity is low and prone to sagging due to high temperatures. It is absolutely prohibited to add water alone to adjust viscosity. Fine adjustments must be made based on solid content, viscosity as an auxiliary, and rheology as the core. The parameters must be recalibrated during seasonal changes, and the Spring and Autumn standards cannot be used.
4. Precise control of pH value
The optimal pH for ceramic tile glaze is in the weak alkaline range of 8.0-9.0. Low pH (neutral/acidic): collapse of inorganic suspended colloid network, rapid settling, layering, hard agglomeration, and rheological failure of glaze slurry; Excessive pH (strong alkalinity): The glaze slurry has strong activity, is prone to foaming, and hydrolysis intensifies. The risk of burning pinholes increases sharply, and at the same time, the color of the pigment deviates.
5. Stability control of suspension system
After the qualified glaze slurry is left to settle, it must form a soft precipitate and be stirred gently to mix evenly; If there is hard precipitation or clumping that cannot be stirred, it indicates that the suspension system has failed (electrolyte exceeding the standard, excessive gelatinization, unhydrated suspension agent, and imbalanced ratio), and production is prohibited from going online.
6. Water and material replenishment standards
It is strictly prohibited to add a large amount of water or original solution at once. Fine tuning must be done in small amounts and multiple times, while adding and stirring, stirring evenly, and retesting parameters; Excessive hydration can instantly disrupt the ion balance of the glaze slurry, leading to flocculation, instability, and rheological drift.
4、 Mechanism, causes, and on-site remediation plan of high-frequency defects during construction process
1. Flow hanging, hanging glaze, and bottom edge accumulation glaze
Core causes: low viscosity of glaze slurry, insufficient thixotropic yield, imbalanced solid content ratio, low body temperature, excessive glaze flow rate, and slow conveying speed.
Radical solution: Fine tune and increase the proportion of inorganic suspension agents to enhance low shear anti sagging performance; Properly increase the temperature of the billet; Reduce glaze flow rate and match conveying speed; Do not simply add water to reduce viscosity.
2. Glaze threads, water ripples, and glaze stripes
Core causes: instability of glaze curtain, unresolved bubbles in glaze slurry, fluctuation of circulating pressure, slow recovery speed of thixotropy, and dry slag formation at the glaze pouring mouth.
Radical solution: Extend the defoaming and settling time; Clean the narrow slit of the glaze applicator; Stabilize the pump body frequency; Optimize the suspension and compounding system to enhance the balance of thixotropy.
3. Uneven thickness of glaze layer, exposed base, and uneven appearance
Core cause: rapid dehydration and crust formation due to high billet temperature; High viscosity and poor fluidity of glaze slurry; The concentration of glaze slurry settling layer varies from top to bottom; The equipment is shaking during transportation.
Radical solution: stabilize the temperature of the billet; Reduce viscosity to the standard range; Strengthen bottom circulation flipping; Calibrate the smoothness of the conveying equipment.
4. Shrinkage glaze, rolling glaze, shrinkage hole needle hole
Core causes: dust and oil stains on the surface of the blank, oil and water in compressed air, uneven surface tension of the glaze slurry, poor local wetting of the glaze layer, and uneven dryness and wetness of the blank.
Radical solution: Strengthen the dust and oil removal of the billet; Inspect the air compressor drying system; Fine tune the wetting and dispersing system; Unified moisture content of the blank body.
5. Batch production of pinholes, bubbles, and rough surfaces
Core causes: mixing brings in a large number of bubbles, CMC organic additives exceed the standard, the moisture content of the body is high, the pH of the glaze slurry is too high, and the glaze layer is too thick.
Radical solution: prohibit high-speed mixing and eliminate foam in advance; Strictly lower the upper limit of organic additives; Strictly control the moisture content of the billet; Reduce the pH of the glaze slurry to a reasonable range.
6. Black spots, impurities, and particle defects
Core causes: high iron impurities in ordinary bentonite, damaged screen mesh, rust detachment from equipment, slag accumulation and mold growth in glaze grooves, and external dust falling in.
Radical solution: Replace magnesium aluminum silicate with high-end glaze; Regularly replace the screen mesh; Glaze groove anti-corrosion and rust prevention; Thoroughly clean the tank and remove debris in each shift.
5、 Standardized precautions for drying, transportation, and storage after glazing
The completion of glaze application does not mean the end of the process. The drying and curing of the glaze directly determine the firing qualification rate, which is a key control point that is easily overlooked.
1. Drying control
After glaze application, it is prohibited to use high-temperature hot air for direct blowing or rapid drying. Rapid single-sided dehydration can cause inconsistent shrinkage inside and outside the glaze layer, leading to cracking, curling, peeling, and delamination of the glaze surface. Gradient gentle drying must be used to ensure uniform dehydration and dense and stable structure of the glaze layer as a whole.
2. Glaze billet transportation standards
Handle with care to prevent collision, friction, and handprint contamination; It is strictly prohibited to stack and squeeze wet glazed blanks to prevent adhesion, deformation, and thickness indentation of the glaze layer; The conveyor belt should be kept clean, and it is forbidden to carry slag or oil.
3. Storage environment requirements
The glaze storage workshop should maintain a constant temperature and humidity to avoid high humidity storage, direct cold air blowing, exposure to sunlight, and drastic temperature changes. In high humidity environments, the glaze layer absorbs moisture and becomes soft, making it prone to foaming and pinholes when fired; The drastic temperature difference causes uneven stress in the glaze layer, leading to glaze cracking and uneven matte finish.
4. Storage cycle control
Glazed glaze should not be stored outdoors for a long time or accumulate dust and dirt. Dust adhering to the glaze will burn white spots, pockmarks, and dull spots; Try to enter the kiln on time after glazing to reduce inventory backlog.
6、 Differentiated fine-tuning plan for seasonal operating conditions
1. Low temperature in winter
Low water temperature and ambient temperature result in slower hydration of the suspension agent, overall higher viscosity of the glaze slurry, and poorer leveling. Process fine-tuning: Extend the pre hydration time of the suspension agent; Appropriately increase inorganic suspension by 0.1-0.2%; Reduce the amount of cellulose used to prevent excessive viscosity; Properly increase the temperature of the body to avoid excessive thickness and sagging of the glaze layer.
2. High temperature in summer
High temperature leads to degradation of organic cellulose, rapid viscosity decay, rapid evaporation of glaze water, and easy foaming. Process fine-tuning: Replace some CMC with heat-resistant HEC/HPMC; Reduce the amount of inorganic suspension appropriately; Strengthen the defoaming of glaze slurry; Strictly control the frequency of water addition to stabilize solid content.
3. High humidity during rainy season
The air humidity is high, causing the body to regain moisture, the glaze layer to dry slowly, and it is prone to moisture absorption and softening. Process fine-tuning: reduce the total amount of organic additives; Properly increase the drying strength of the billet; Extend the pre drying time of the glaze blank and prevent wet glaze blanks from directly entering the kiln.
7、 Stability of mass production batches and control of material and line changes
1. For each batch of glaze, color, and formula changes, the solid content and viscosity must be retested pH、 Flat state, prohibit using old parameters.
2. To replace the suspension agent, melt block, and pigment supplier, a small trial run must be conducted first to confirm that there are no defects before mass production.
3. It is prohibited to retain old materials for a long time in the glaze groove as they may cause continuous defects in the next batch due to coagulation, aging, and degradation of the old materials.
4. Establish a ledger for “glaze slurry parameters – glaze thickness – firing effect”, form a data loop, and thoroughly solve batch fluctuations.
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Post time: Aug-31-2026