Low-shading high-contrast reddish brown colored drawing porcelain glaze and preparation method thereof

Abstract

The invention discloses a low-shading high-contrast reddish brown colored drawing porcelain glaze and a preparation method thereof, and belongs to the technical field of inorganic non-metallic materials. The porcelain glaze comprises the following components in percentage by mass: 20%-30% of quartz, 20%-35% of feldspar, 8%-15% of calcite, 15%-25% of kaolin, 15%-25% of pre-sintered iron-rich clay, 0.5%-1.0% of sodium carboxymethyl cellulose and 0.2%-0.5% of sodium tripolyphosphate. Wherein the pre-sintered iron-rich clay is prepared by pre-sintering natural iron-rich clay at 700-900 DEG C, and the content of Fe2O3 is 5%-8%. The preparation method comprises the following steps: pre-sintering the iron-rich clay, mixing the pre-sintered iron-rich clay with other glaze raw materials, carrying out ball milling to obtain glaze slip, applying the glaze slip to a glaze blank, preheating, and carrying out heat preservation sintering in an oxidizing atmosphere of 1180-1220 DEG C. The iron element crystal form is stabilized through pre-sintering treatment, a specific glaze formula and an optimized sintering system are combined, anorthite microcrystals which are decomposed and promoted by calcite are used for wrapping alpha-Fe2O3 colored particles, iron ion migration is effectively inhibited, the technical problems that traditional reddish brown colored drawing patterns are blurred, and boundaries are blurred are solved, and the service life of the reddish brown colored drawing is prolonged. And the high-quality colored drawing porcelain with bright and saturated color, high contrast ratio and clear pattern is obtained.

Description

Technical Field

[0001] This invention relates to the field of inorganic non-metallic materials technology, specifically to a low-bleeding, high-contrast reddish-brown painted porcelain glaze and its preparation method. Background Technology

[0002] Reddish-brown painted porcelain is an important category of traditional iron-based underglaze porcelain. It uses iron-containing minerals as colorants and, after firing in an oxidizing atmosphere, achieves a rustic and elegant reddish-brown decorative effect. Unlike white-ground black-decorated porcelain, which uses mottled stone to form black glaze under a reducing atmosphere, reddish-brown glaze requires the formation of stable α-Fe₂O₃ (hematite) crystals under an oxidizing atmosphere to develop its color. However, in actual firing processes, fluctuations in mineral raw material composition and improper firing control can easily lead to iron ion migration and diffusion, causing problems such as pattern blurring, indistinct boundaries, and unstable hues, severely affecting the artistic effect and yield of the painted decoration.

[0003] Currently, there is a lack of effective methods for systematically controlling the smudges and contrast of reddish-brown enamel paintings. In particular, how to stabilize the formation of α-Fe2O3 crystals and inhibit iron ion migration by pretreating iron-rich mineral raw materials and combining them with an oxidation firing process remains a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a low-bleeding, high-contrast reddish-brown painted porcelain glaze and its preparation method. By selecting iron-rich clay raw materials, adopting a pre-firing process, and precisely controlling the oxidizing atmosphere firing regime, the coloring behavior and crystal formation process of iron elements are regulated, thereby enabling the reddish-brown painted porcelain glaze to exhibit a low-bleeding, high-contrast effect.

[0005] This invention is achieved through the following technical solution: A low-bleeding, high-contrast reddish-brown painted porcelain glaze, comprising the following components by weight percentage: Quartz 20%~30%, Feldspar 20%~35%, Calcite 8%~15%, Kaolin 15%~25%, Pre-fired iron-rich clay 15%~25%, Sodium carboxymethyl cellulose 0.5%~1.0%, Sodium tripolyphosphate 0.2%~0.5%; The pre-fired iron-rich clay is obtained by pre-firing natural iron-rich clay at 700℃~900℃, and its Fe2O3 content is 5%~8%.

[0006] Preferably, the quartz is at least one of natural quartz and synthetic quartz.

[0007] Preferably, the feldspar is at least one of potassium feldspar, sodium feldspar, and calcium feldspar.

[0008] A method for preparing a low-bleeding, high-contrast reddish-brown painted porcelain glaze includes the following steps: Step 1: Pre-fire the iron-rich clay raw material at 700℃~900℃ to obtain pre-fired iron-rich clay; Step 2: Mix the pre-fired iron-rich clay and other glaze raw materials and then perform wet ball milling to obtain a reddish-brown painted glaze slurry; Step 3: Apply the reddish-brown painted glaze obtained in step S2 onto the glazed body, and let it dry to obtain the painted body; Step 4: Preheat the colored blank obtained in step S3, and then heat it to 1180℃~1220℃ in an oxidizing atmosphere for holding and firing. After natural cooling, the low-bleeding, high-contrast reddish-brown painted porcelain glaze is obtained.

[0009] Preferably, the wet ball milling process conditions are as follows: the mass ratio of raw material, milling stone, and water is 1:1.2:0.8, and the specific gravity of the resulting glaze slurry is 1.50 g / cm³. 3 ~ 1.60 g / cm 3 .

[0010] Preferably, the wet ball milling process conditions further include: The ball milling speed is 280 r / min ~ 320 r / min, and the ball milling time is 50 min ~ 60 min.

[0011] Preferably, the specific preheating conditions are: preheating at 800℃~900℃ for 2~4 hours.

[0012] Preferably, the specific conditions for the heat preservation firing are: heat preservation in an oxidizing atmosphere at 1180℃~1220℃ for 15~30 minutes.

[0013] A type of porcelain comprising a white glazed body and a reddish-brown painted glaze layer attached thereto.

[0014] Preferably, the glaze body comprises 35%~40% kaolin, 25%~30% feldspar, 15%~20% quartz and 10%~20% porcelain stone.

[0015] Compared with the prior art, the present invention has the following beneficial technical effects: This application provides a low-bleeding, high-contrast reddish-brown painted porcelain glaze. It introduces pre-fired iron-rich clay, pre-fired at 700℃~900℃ with Fe2O3 content controlled at 5%~8%, as a key colorant. This fundamentally solves the problem of pattern bleeding and blurred boundaries caused by iron ion migration in traditional reddish-brown painted porcelain. The pre-firing treatment promotes the pre-conversion of iron elements into thermally stable α-Fe2O3 crystals, significantly improving the chemical inertness of the colorant during subsequent high-temperature firing. Simultaneously, the CaO produced by the decomposition of 8%~15% calcite in the formula during firing can react with other components in the glaze to form anorthite microcrystals. These microcrystals effectively encapsulate and anchor α-Fe2O3 particles, inhibiting their diffusion and migration. Other components, such as quartz, feldspar, kaolin, and small amounts of sodium carboxymethyl cellulose and sodium tripolyphosphate, together constitute a suitable glaze matrix, ensuring good process performance, glaze surface smoothness, and bonding strength with the body. This composition range represents the optimal balance point for achieving a low-bleeding, high-contrast decorative effect. If the component content is too low or too high, it will be difficult to simultaneously achieve ideal color rendering, stability, and glaze quality.

[0016] The method for preparing the painted porcelain glaze provided in this application begins with a pre-firing treatment of iron-rich clay raw materials at 700℃~900℃. This step is crucial for stabilizing the colorant crystal form, removing impurities and water of crystallization, and reducing gas release during subsequent high-temperature firing, directly determining the clarity and color stability of the final pattern. Subsequently, a wet ball milling process ensures that all components, especially the pre-fired iron-rich clay, are uniformly dispersed in the glaze slurry, forming a stable painted glaze slurry system. After applying the color to the glaze body, the key firing regime employs a specific procedure of preheating at 800~900℃ followed by holding at 1180~1220℃ in an oxidizing atmosphere. This firing process complements the pre-firing treatment and glaze composition: the preheating stage helps decompose organic matter and release stress, while the specific high-temperature oxidation and heat preservation stage precisely promotes the stable precipitation and growth of α-Fe2O3 microcrystals and optimizes the formation of glaze structure such as anorthite microcrystals, thereby firmly locking in the colorant and maximally suppressing the high-temperature migration of iron ions. This ensures that the final product can stably achieve a low-bleeding, high-contrast reddish-brown decorative effect, with high repeatability and industrial utilization value. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a cross-sectional view of the reddish-brown painted porcelain glaze of the present invention. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0021] A low-bleeding, high-contrast reddish-brown painted porcelain glaze, comprising, by weight percentage: 20%~30% quartz, 20%~35% feldspar, 8%~15% calcite, 15%~25% kaolin, 15%~25% pre-fired iron-rich clay, 0.5%~1.0% sodium carboxymethyl cellulose and 0.2%~0.5% sodium tripolyphosphate.

[0022] The quartz is at least one of natural quartz and synthetic quartz, and is the main skeleton component of the glaze, providing good high-temperature resistance and chemical stability.

[0023] The feldspar is at least one of potassium feldspar, sodium feldspar, and calcium feldspar, and plays a role in fluxing and lowering the melting temperature in the glaze.

[0024] Calcite is an important flux in the glaze, mainly providing CaO, with its content controlled between 8% and 15%. When its content exceeds 8%, during high-temperature firing, the CaO produced by the decomposition of calcite will react with Al2O in the glaze. 3、 SiO2 reacts to form anorthite (CaAl2Si2O8) microcrystals. These precipitated anorthite microcrystals effectively encapsulate α-Fe2O3 colorant particles, physically isolating them and significantly inhibiting the migration and diffusion of iron ions in the glaze melt. This is one of the key mechanisms for achieving low bleeding and high contrast in painted patterns. However, its content should not exceed 15%, otherwise it will lead to excessive opacity in the glaze surface, affecting the vibrancy of the reddish-brown color. The kaolin is one of the key components in the glaze, possessing good plasticity and binding properties, which can enhance the adhesion and formability of the glaze.

[0025] The pre-fired iron-rich clay is the main colorant for underglaze painting decoration. It is made from natural iron-rich clay through pre-firing at 700~900℃, which converts the iron element into stable α-Fe2O3, resulting in bright reddish-brown patterns. Its Fe2O3 content is controlled at 5%~8%.

[0026] The sodium carboxymethyl cellulose (CMC-Na) has good thickening, water retention and binding properties, which can improve the stability of the glaze slurry and the smoothness of the finished glaze surface.

[0027] The sodium tripolyphosphate, as a dispersant, helps improve the fluidity and stability of the glaze and strengthens the bond between the glaze and the body.

[0028] Correspondingly, this application also provides a type of porcelain, comprising a white glazed body and a reddish-brown painted glaze layer attached to its surface.

[0029] By weight percentage, the glaze body comprises 35%–40% kaolin, 25%–30% feldspar, 15%–20% quartz, and 10%–20% porcelain stone.

[0030] By weight percentage, the reddish-brown painted glaze layer comprises: 20%–30% quartz, 20%–35% feldspar, 8%–15% calcite, 15%–25% kaolin, 15%–25% pre-fired iron-rich clay, 0.5%–1.0% sodium carboxymethyl cellulose, and 0.2%–0.5% sodium tripolyphosphate.

[0031] Correspondingly, this application also provides a method for preparing a low-bleeding, high-contrast reddish-brown painted porcelain glaze, comprising the following steps: Step 1: Prepare the glaze blank: The clay body is made by crushing the raw materials (35%~40% kaolin, 25%~30% feldspar, 15%~20% quartz and 10%~20% porcelain stone); the clay body is then repeatedly pounded by hand to remove excess gas, shaped, and dried to obtain the body; a transparent glaze is applied to make a glazed body, which is then left to stand for later use.

[0032] Step 2, Pre-treatment of pigments: The iron-rich clay raw material is pre-calcined at 700~900℃ to promote its conversion into stable α-Fe2O3.

[0033] Pre-firing (700~900℃) allows the iron in iron-rich clay to transform into α-Fe2O3 crystals in advance, while simultaneously removing water of crystallization and organic matter. Because α-Fe2O3 crystals have high thermal stability, they are less likely to decompose into free Fe³⁺ during high-temperature firing (free Fe³⁺ easily migrates and causes bleed-through). Pre-firing also reduces gas release during firing, preventing the formation of micropores in the glaze layer (micropores become channels for Fe³⁺ migration). Therefore, pre-firing reduces the migration ability of iron ions from the "source," laying the foundation for "low bleed-through."

[0034] The calcite content is 8%~15%, because calcite decomposes into CaO at high temperatures. CaO reacts with Al2O3 and SiO2 in the glaze to form anorthite microcrystals. These anorthite microcrystals are the core material that "encapsulates α-Fe2O3 particles," causing them to be distributed in a cage-like pattern. This contrasts quantitatively with the highly diffused "iron ion diffusion halo (10-20μm wide)," directly affecting the degree of diffusion. These microcrystals encapsulate the α-Fe2O3 coloring particles like "cages," physically isolating free Fe³⁺ and completely inhibiting its migration, ultimately achieving "clear pattern boundaries and strong contrast between color and white glaze." When the calcite content is below 8%, "anorthite formation is insufficient, and it cannot completely encapsulate α-Fe2O3," and when it is above 15%, "the glaze opacity increases, and the brightness of the reddish-brown color decreases."

[0035] Step 3: Prepare the glaze for painting: Weigh the iron-rich clay and other glaze raw materials (quartz, feldspar, calcite, kaolin, sodium carboxymethyl cellulose and sodium tripolyphosphate) from step 2 according to the specified ratio, and use wet ball milling to obtain a reddish-brown painted glaze slurry. During the ball milling process, the ratio of raw materials: milling stone: water is 1:1.2:0.8, the ball milling speed is 280~320 r / min, the time is 50~60 min, and the specific gravity of the glaze slurry is controlled to be 1.50-1.60 g / cm³.

[0036] Step 4, Apply color: The reddish-brown glaze obtained in step 3 is applied to the glaze blank prepared in step 1 using the drawing method, and after drying, the glazed blank is obtained.

[0037] Step 5, firing: The colored blank obtained in step 4 is preheated at 800-900℃ for 2-4 hours; after preheating, the temperature is further increased to 1180-1220℃ and fired in an oxidizing atmosphere for 15-30 minutes. After natural cooling, the low-bleeding, high-contrast reddish-brown painted porcelain glaze is obtained.

[0038] This method introduces zinc phosphate stabilizer, optimizes the ratio of iron and manganese colorants, and adopts an oxidizing atmosphere firing process to control the color development process and interface behavior of red-brown painted glaze, thereby enabling the red-brown painted porcelain glaze to exhibit a low-bleeding and high-contrast effect.

[0039] This invention utilizes pre-firing treatment (700~900℃) of iron-rich clay to effectively remove organic impurities and water of crystallization from the raw materials, promoting the transformation of iron into a stable α-Fe2O3 crystal form, thus greatly improving the thermal and chemical stability of the colorant. Pre-firing also promotes carbonate decomposition, reduces gas release during firing, and avoids bubbles and glaze defects. Pre-fired colorant particles are uniform and have better dispersion in the glaze slurry, which is beneficial for painting operations and the formation of a uniform and dense glaze layer. Combined with an optimized oxidation firing regime, it effectively promotes the precipitation and growth of α-Fe2O3 microcrystals, firmly anchoring them in the glaze layer and fundamentally inhibiting the high-temperature migration of iron ions. This results in a decorative effect with clear pattern boundaries, vibrant and saturated colors, and extremely high contrast, significantly improving production efficiency and product qualification rate.

[0040] Example 1 A low-bleeding, high-contrast reddish-brown painted porcelain glaze, the composition of which is as follows (by weight percentage): Quartz: 20% Feldspar: 35% Calcite: 8% Kaolin: 25% Pre-fired iron-rich clay (Fe2O3 content 5%): 15% Sodium carboxymethyl cellulose: 0.5% Sodium tripolyphosphate: 0.2% The preparation method of this low-bleeding, high-contrast reddish-brown painted porcelain glaze is as follows: Step 1: Prepare the glaze blank: Step 2: Pre-fire the iron-rich clay at 700℃ for 2 hours to convert it into α-Fe2O3.

[0041] Step 3: Mix the pre-fired iron-rich clay with the remaining raw materials according to the specified ratio, add an appropriate amount of water, and wet ball mill at a ratio of raw materials:milling stone:water = 1:1.2:0.8, at a speed of 280 r / min for 60 min to obtain a glaze slurry with a specific gravity of 1.50 g / cm³. 3 .

[0042] Step 4: Apply the glaze paste onto the glazed body with the transparent glaze and let it dry.

[0043] Step 5: Preheat the glaze blank at 800℃ for 4 hours, then raise the temperature to 1180℃ and hold for 30 minutes in an oxidizing atmosphere, and let it cool naturally.

[0044] The resulting porcelain glaze pattern has clear boundaries, a bright reddish-brown color, slight smudging, and high contrast.

[0045] Example 2 A low-bleeding, high-contrast reddish-brown painted porcelain glaze, the composition of which is as follows (by weight percentage): Quartz: 25% Feldspar: 28% Calcite: 12% Kaolin: 20% Pre-fired iron-rich clay (Fe2O3 content 6.5%): 20% Sodium carboxymethyl cellulose: 0.8% Sodium tripolyphosphate: 0.35% The preparation method of this low-bleeding, high-contrast reddish-brown painted porcelain glaze is as follows: Step 1: Prepare the glaze blank: Step 2: Pre-fire the iron-rich clay at 800℃ for 1.5 hours to convert it into α-Fe2O3.

[0046] Step 3: Mix the pre-fired iron-rich clay with the remaining raw materials according to the specified ratio, add an appropriate amount of water, and wet ball mill at a ratio of raw materials:milling stone:water = 1:1.2:0.8, at a speed of 300 r / min for 55 min to obtain a glaze slurry with a specific gravity of 1.55 g / cm³. 3 .

[0047] Step 4: Apply the glaze paste onto the glazed body with the transparent glaze and let it dry.

[0048] Step 5: Preheat the glaze blank at 850℃ for 3 hours, then raise the temperature to 1200℃ and hold for 20 minutes in an oxidizing atmosphere, and let it cool naturally.

[0049] The resulting porcelain glaze pattern has clear boundaries, saturated colors, excellent contrast, and no smudging.

[0050] Example 3 A low-bleeding, high-contrast reddish-brown painted porcelain glaze, the composition of which is as follows (by weight percentage): Quartz: 30% Feldspar: 20% Calcite: 15% Kaolin: 15% Pre-fired iron-rich clay (Fe2O3 content 8%): 25% Sodium carboxymethyl cellulose: 1.0% Sodium tripolyphosphate: 0.5% The preparation method of this low-bleeding, high-contrast reddish-brown painted porcelain glaze is as follows: Step 1: Prepare the glaze blank: Step 2: Pre-fire the iron-rich clay at 900℃ for 1 hour to convert it into α-Fe2O3.

[0051] Step 3: Mix the pre-fired iron-rich clay with the remaining raw materials according to the specified ratio, add an appropriate amount of water, and wet ball mill at a ratio of raw materials:milling stone:water = 1:1.2:0.8, at a speed of 320 r / min for 50 min to obtain a glaze slurry with a specific gravity of 1.60 g / cm³. 3 .

[0052] Step 4: Apply the glaze paste onto the glazed body with the transparent glaze and let it dry.

[0053] Step 5: Preheat the glaze blank at 900℃ for 2 hours, then raise the temperature to 1220℃ and hold for 15 minutes in an oxidizing atmosphere, and let it cool naturally.

[0054] The resulting porcelain glaze pattern has clear boundaries, saturated colors, excellent contrast, and no smudging.

[0055] See Figure 1 The reddish-brown painted porcelain glaze prepared by the method of this invention shows that the α-Fe2O3 particles in the image are regular in shape and without agglomeration, confirming that the pre-firing at 700-900℃ has transformed the iron element in the iron-rich clay into a stable crystal form, avoiding the generation of free Fe³+ (free Fe³+ will form a diffusion halo, corresponding to the blurred edges in the highly stained image). The anorthite microcrystals (generated by the reaction of CaO decomposed from calcite with Al2O3 and SiO2) are distributed in a continuous network, like "miniature cages", locking the α-Fe2O3 particles in a fixed area and physically isolating the migration path of Fe³+ at high temperature - this is the core structural basis of "low stainedness"; at the same time, the high temperature accelerates the formation of anorthite microcrystals, and the short heat preservation of 15-30 minutes avoids the excessive growth of α-Fe2O3 particles, making the α-Fe2O3 particle size uniform (2-5μm) and the color saturated; at the same time, the glaze layer is dense and without micropores (no migration channels), further suppressing stainedness.

[0056] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A low-bleeding, high-contrast reddish-brown painted porcelain glaze, characterized in that, By mass percentage, it includes the following components: Quartz 20%~30%, Feldspar 20%~35%, Calcite 8%~15%, Kaolin 15%~25%, Pre-fired iron-rich clay 15%~25%, Sodium carboxymethyl cellulose 0.5%~1.0%, Sodium tripolyphosphate 0.2%~0.5%; The pre-fired iron-rich clay is obtained by pre-firing natural iron-rich clay at 700℃~900℃, and its Fe2O3 content is 5%~8%.

2. The low-bleeding, high-contrast reddish-brown painted porcelain glaze according to claim 1, characterized in that, The quartz is at least one of natural quartz and synthetic quartz.

3. The low-bleeding, high-contrast reddish-brown painted porcelain glaze according to claim 1, characterized in that, The feldspar is at least one of potassium feldspar, sodium feldspar, and calcium feldspar.

4. A method for preparing a low-bleeding, high-contrast reddish-brown painted porcelain glaze according to any one of claims 1-3, characterized in that, Includes the following steps: Step 1: Pre-fire the iron-rich clay raw material at 700℃~900℃ to obtain pre-fired iron-rich clay; Step 2: Mix the pre-fired iron-rich clay and other glaze raw materials and then perform wet ball milling to obtain a reddish-brown painted glaze slurry; Step 3: Apply the reddish-brown painted glaze obtained in step S2 onto the glazed body, and let it dry to obtain the painted body; Step 4: Preheat the colored blank obtained in step S3, and then heat it to 1180℃~1220℃ in an oxidizing atmosphere for holding and firing. After natural cooling, the low-bleeding, high-contrast reddish-brown painted porcelain glaze is obtained.

5. The method for preparing the low-bleeding, high-contrast reddish-brown painted porcelain glaze according to claim 4, characterized in that, The wet ball milling process conditions are as follows: the mass ratio of raw material, milling stone, and water is 1:1.2:0.8, and the specific gravity of the resulting glaze slurry is 1.50 g / cm³. 3 ~ 1.60 g / cm 3 .

6. The method for preparing low-bleeding, high-contrast reddish-brown painted porcelain glaze according to claim 5, characterized in that, The process conditions for wet ball milling also include: The ball milling speed is 280 r / min ~ 320 r / min, and the ball milling time is 50 min ~ 60 min.

7. The method for preparing low-bleeding, high-contrast reddish-brown painted porcelain glaze according to claim 4, characterized in that, The specific preheating conditions are: preheating at 800℃~900℃ for 2~4 hours.

8. The method for preparing low-bleeding, high-contrast reddish-brown painted porcelain glaze according to claim 4, characterized in that, The specific conditions for the heat preservation firing are: heat preservation at 1180℃~1220℃ in an oxidizing atmosphere for 15~30 minutes.

9. A type of porcelain, characterized in that, It includes a white glazed body and a reddish-brown painted glaze layer as described in any one of claims 1-3 adhering to its surface.

10. A type of porcelain according to claim 19, characterized in that, The glaze body comprises 35%~40% kaolin, 25%~30% feldspar, 15%~20% quartz and 10%~20% porcelain stone.

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