An antique-style ceramic brick

Abstract

This invention relates to an antique-style ceramic tile, belonging to the field of architectural ceramics technology. The antique-style ceramic tile provided by this invention comprises, in sequence, a body layer, a base glaze layer, a pattern layer, a functional ink layer, and a surface glaze layer. The raw materials for preparing the base glaze layer include specific weight parts of air-knife clay, calcined kaolin, wollastonite, strontium carbonate, zirconium silicate, nano-alumina, potassium feldspar, and sodium feldspar. The raw materials for preparing the surface glaze layer include specific weight parts of calcined kaolin, air-knife clay, nano-alumina, wollastonite, matte frit, nano-silica, nano-zinc oxide, talc, polyacrylate microspheres, potassium feldspar, and sodium feldspar. The antique-style ceramic tile provided by this invention has a gloss level ≤3°, possessing a essentially matte glaze surface, achieving a non-glaring, non-dazzling, and elegant decorative effect; it also has a delicate, smooth, and warm texture, not rough or dry to the touch; and it also exhibits excellent stain resistance, wear resistance, and acid and alkali resistance.

Description

Technical Field

[0001] This invention relates to the field of building ceramics technology, and in particular to an antique-style ceramic brick. Background Technology

[0002] Currently, traditional matte ceramic tiles generally suffer from the following problems: the glaze gloss is still too high (usually ≥5°), which cannot meet the needs of minimalist style decoration; the surface has a microporous structure that easily traps dirt and grime, making cleaning difficult; insufficient wear resistance, resulting in easy wear and tear on the texture; and a monotonous texture, lacking aesthetic appeal and depth.

[0003] Existing matte antique-style products primarily achieve their matte finish by increasing the glaze formulation temperature and controlling the flux during firing to create diffuse reflection. However, the gloss level of these products is generally 6-8° or higher, resulting in visible surface shine under light, failing to achieve a natural, elegant, and authentic antique texture. Research into low-gloss antique-style tiles often involves adding excessive high-melting-point materials to the glaze, resulting in an under-fired state. This creates closed pores within the glaze layer, making it prone to absorbing and trapping dirt, affecting aesthetics and increasing cleaning costs. Furthermore, lowering the gloss level can lead to a rougher glaze surface with less refined texture and lower wear resistance, causing wear during use and shortening its lifespan.

[0004] Therefore, there is an urgent need to develop an antique-style ceramic tile with a better matte finish, which also needs to have a delicate and smooth warm texture, as well as superior stain resistance, wear resistance, and acid and alkali resistance. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide an antique-style ceramic tile. The antique-style ceramic tile provided by this invention has a basically matte glaze, a delicate and smooth texture, and excellent stain resistance, wear resistance, and acid and alkali resistance.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] In a first aspect, the present invention provides an antique ceramic tile, which sequentially comprises a body layer, a base glaze layer, a pattern layer, a functional ink layer, and a surface glaze layer;

[0008] The raw materials for preparing the base glaze layer include the following components in parts by weight: 4-10 parts of air knife clay, 12-18 parts of calcined kaolin, 3-6 parts of wollastonite, 7-11 parts of strontium carbonate, 6-12 parts of zirconium silicate, 3-6 parts of nano alumina, 22-30 parts of potassium feldspar, and 25-30 parts of sodium feldspar.

[0009] The raw materials for preparing the surface glaze layer include the following components in parts by weight: calcined kaolin 7.5-12.5 parts, air knife clay 4-8 parts, nano alumina 4-9 parts, wollastonite 8-12 parts, matte frit 20-30 parts, nano silica 1-5 parts, nano zinc oxide 2-6 parts, talc powder 4-8 parts, polyacrylate microspheres 2-6 parts, potassium feldspar 10-17 parts, and sodium feldspar 8-16 parts.

[0010] The antique ceramic tile provided by this invention achieves an antique glaze effect with a matte finish and delicate texture through the reasonable selection and combination of raw materials for the base glaze layer and the surface glaze layer. Its gloss level is ≤3°, and it also has excellent self-cleaning properties, as well as wear resistance and acid and alkali resistance.

[0011] In the base glaze layer, the air-knife clay primarily provides suspension for the glaze, while its organic matter provides viscosity, ensuring uniform distribution of material particles before glazing and guaranteeing uniformity during subsequent glazing. It also provides the chemical components Al2O3 and SiO2, forming the main framework of the glaze after firing and the primary components of the mullite crystal phase. Calcined kaolin also provides Al2O3 and SiO2, while simultaneously improving the firing range and high-temperature viscosity of the base glaze, ensuring good smoothness and hiding power. Potassium feldspar and sodium feldspar primarily provide the monovalent oxide K2O. Na₂O acts as a flux to lower the melting temperature of the formula, promoting the formation of the glassy phase during firing and accelerating the maturation of the glaze. Wollastonite mainly provides divalent oxide CaO, which can reduce high-temperature viscosity during firing, promote the maturation of the glaze, and form anorthite crystals, increasing the strength of the glaze layer. Strontium carbonate mainly provides SrO after firing, which not only makes the base glaze easier to fire but also helps to reduce the gloss of the glaze surface. Zirconium silicate mainly provides ZrO₂, which mainly improves the whiteness and hiding power of the base glaze, and is more conducive to the color development of the product.

[0012] The present invention also uses nano-sized alumina in the surface glaze layer. Its main function is to broaden the firing temperature of the base glaze, increase the hardness of the base glaze layer, form mullite crystals after firing, increase the strength of the glaze layer, and ensure that the base glaze is smoother, providing a better base for the delicate and warm texture of the tile surface.

[0013] In the surface glaze layer, calcined kaolin and air-knife clay form the main framework, echoing the high-alumina formula in the base glaze to create a glaze system with similar light refractive indices. This improves the glaze slurry suspension, strengthens the bond between the body and glaze, and, together with talc, promotes microcrystalline structure, further reducing gloss. Wollastonite primarily provides CaO; introducing CaO crystals into the glaze layer improves its wear resistance. Simultaneously, the introduction of a calcium network enhances wear resistance and promotes microcrystalline precipitation, synergistically with talc for matting. Talc forms magnesium silicates, which reduce gloss and regulate the coefficient of thermal expansion, minimizing the risk of cracking. Potassium feldspar and sodium feldspar primarily act as solvent aids.

[0014] Meanwhile, the present invention also employs three types of nano-oxide particles in the surface glaze layer, which can synergistically construct a framework structure that assists in matting, wear resistance, stain resistance, and self-cleaning:

[0015] Among them, after firing, the nano-alumina, with its numerous nano-micropores and mullite crystals, ensures the strength and wear resistance of the glaze layer, reduces glaze wear during product use, and improves glaze hardness; nano-zinc oxide has the effect of high-temperature fluxing, which can broaden the firing range of the glaze; nano-silica aerogel can combine with nano-alumina to form a gradient structure, enhancing the anti-fouling properties of the glaze.

[0016] The three types of nanoparticles mentioned above work together to construct a wear-resistant framework and form submicron-level surface irregularities, which can help to matte and reduce gloss, and work synergistically with polyacrylate microspheres to achieve a "self-cleaning" effect: the polyacrylate microspheres are distributed in the sub-surface or surface layer of the glaze layer, and after burning, they form closed pores, which can reduce the contact between contaminants entering the surface and the deeper layers; while the micro-nano structure framework constructed by the three types of particles can anchor contaminants on the glaze surface. Combined with the good flexibility of the polyacrylate microspheres, contaminants are more easily desorbed from the surface under the drive of environmental forces (such as rain, sunlight, temperature rise, etc.), achieving self-cleaning without human intervention.

[0017] This invention primarily addresses the problem of excessively high gloss in existing antique-style ceramic tiles by optimizing the formulations of the base glaze and top glaze layers, providing a product with a essentially matte glaze surface. It also solves the problems of poor stain resistance and wear resistance found in existing matte glaze products. The base and top glaze formulations provided by this invention, after firing, create a glaze layer that combines a delicate feel, stain resistance, wear resistance, and durability with an excellent matte finish, enabling the commercialization of a series of low-gloss, high-performance products.

[0018] Preferably, the particle size of the nano-alumina is 20-50 nm.

[0019] Preferably, the particle size of the nano-silica is 50-100 nm.

[0020] Preferably, the particle size of the nano zinc oxide is 80-120 nm.

[0021] By using a combination of nano-sized particles with specific particle sizes, the wear resistance and acid and alkali resistance of the surface glaze can be comprehensively improved.

[0022] Preferably, the particle size of the polyacrylate microspheres is 250-350 μm.

[0023] The present invention preferably uses organic polyacrylate microspheres to improve the tactile feel and regulate the stress distribution of the glaze layer to prevent cracking.

[0024] Preferably, the raw materials for preparing the base glaze layer include the following components in parts by weight: 6-8 parts of air-knife clay, 14-16 parts of calcined kaolin, 4-5 parts of wollastonite, 8-10 parts of strontium carbonate, 6-7 parts of zirconium silicate, 4-5 parts of nano-alumina, 24-26 parts of potassium feldspar, and 27-29 parts of sodium feldspar.

[0025] Preferably, the raw materials for preparing the surface glaze layer include the following components in parts by weight: 9-11 parts calcined kaolin, 5-7 parts air-knife clay, 5.5-7.5 parts nano alumina, 9-11 parts wollastonite, 24-26 parts matte frit, 2-4 parts nano silica, 3-5 parts nano zinc oxide, 5-7 parts talc, 3-5 parts polyacrylate microspheres, 13-14 parts potassium feldspar, and 11-13 parts sodium feldspar.

[0026] Preferably, in the raw materials for preparing the surface glaze layer, the mass ratio of nano-alumina to nano-zinc oxide is (6.2-6.8):(3.7-4.3).

[0027] Nano-alumina and nano-zinc oxide in specific ratios can further improve the wear resistance of the formed glaze layer.

[0028] Preferably, in the raw materials for preparing the surface glaze layer, the mass ratio of nano-silica to polyacrylate microspheres is (2.8-3.2):(3.6-4.4).

[0029] Nano-silica and polyacrylate microspheres in a specific ratio can further improve the self-cleaning effect of the formed glaze layer.

[0030] As a preferred embodiment of the present invention, the raw materials for preparing the surface glaze layer include nano-alumina, nano-zinc oxide and nano-silica in a mass ratio of (6.2-6.8):(3.7-4.3):(2.8-3.2).

[0031] By constructing a micro / nano framework using nano-alumina, nano-zinc oxide, and nano-silica in a specific mass ratio, the optimal surface texture, wear resistance, acid and alkali resistance, and self-cleaning properties can be achieved.

[0032] Preferably, the matte frit comprises the following components in weight percentage: 17.52-22.54% Al2O3, 41.02-46.65% SiO2, 1.57-5.65% K2O, 1.25-4.87% Na2O, 6.58-11.57% BaO, 2.14-7.59% SrO, 3.54-9.52% ZnO, 1.36-5.68% CaO, and 1.05-6.67% MgO.

[0033] The aforementioned specific matte frit is rich in alkali metal and alkaline earth metal oxides, which can reduce the gloss of the glaze and at the same time reduce the roughness of the matte glaze.

[0034] Secondly, the present invention provides a method for preparing the above-mentioned antique ceramic bricks, comprising the following steps:

[0035] S1. Applying the base glaze: Press and dry the brick blanks, then apply a base glaze slurry to the dried brick blanks. The amount of base glaze applied is 250-350 g / m². 2 ;

[0036] S2. Applying Surface Glaze: The brick blanks, after being coated with a base glaze, are inkjet printed, followed by the application of a surface glaze slurry. The glaze application rate is 150-200 g / m². 2 ;

[0037] S3. Firing: The glazed brick blanks are fired at 1180-1195 ℃ for 50-60 minutes to obtain the antique ceramic bricks.

[0038] Preferably, in step S1, the dried brick blank has a moisture content of 0.3-0.5% and a modulus of rupture ≥1.8 MPa. This ensures sufficient strength for subsequent glazing.

[0039] Preferably, the specific gravity of the base glaze slurry is 1.85-1.92 g / mL, and the specific gravity of the surface glaze slurry is 1.30-1.35 g / mL.

[0040] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0041] (1) The antique ceramic tile provided by the present invention can achieve a gloss level of less than 2° on the surface glaze, so that the surface of the tile is basically without glare when exposed to natural light, and is not dazzling or dizzying, and achieves an elegant and antique decorative effect.

[0042] (2) The antique ceramic tiles provided by the present invention have a delicate and smooth texture, are not rough or dry, and have an overall warm and moist feel;

[0043] (3) The antique ceramic tile provided by the present invention further improves the glaze formula. On the basis of achieving a glossy effect with basically no gloss, it also has a better anti-fouling, wear-resistant and acid and alkali synergistic effect, and has high practical value. Attached Figure Description

[0044] Figure 1 This is a matte finish image of the antique ceramic tile in Embodiment 1 of the present invention.

[0045] Figure 2 This is a matte finish image of the antique ceramic tiles in Comparative Example 6. Detailed Implementation

[0046] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods; the materials and reagents used, unless otherwise specified, are commercially available reagents and materials.

[0047] Examples 1-10 and Comparative Examples 1-13

[0048] The antique ceramic tiles in the following embodiments and comparative examples all include, in sequence, a body layer, a base glaze layer, a pattern layer, a functional ink layer, and a surface glaze layer.

[0049] The methods for preparing antique ceramic tiles in Examples 1-10 and Comparative Examples 1-13 all include the following steps:

[0050] S1. Applying the base glaze: Press and dry the brick blanks (moisture content 0.3%, modulus of rupture 2.0 MPa), then apply the base glaze slurry to the dried brick blanks. The amount of base glaze applied is 300 g / m². 2 The specific gravity of the base glaze slurry is 1.89 g / mL;

[0051] S2. Applying Surface Glaze: The brick blanks that have undergone base glazing are inkjet printed, followed by the application of a surface glaze slurry. The glaze application rate is 180 g / m². 2 The specific gravity of the surface glaze slurry is 1.30 g / mL;

[0052] S3. Firing: The glazed brick blanks are fired at 1185 ℃ for 50 min to obtain the antique ceramic bricks.

[0053] The weight composition of the base glaze formulations 1-8 and the surface glaze formulations 1-12 used in the embodiments and comparative examples is shown in Tables 1 and 2 below.

[0054] The only difference between base glaze formulation 9 and base glaze formulation 1 is that nano alumina is replaced with an equal amount of micron-sized alumina.

[0055] The only difference between base glaze formulation 10 and base glaze formulation 1 is that strontium carbonate is replaced with an equal amount of calcium carbonate.

[0056] The only difference between surface glaze formulation 13 and surface glaze formulation 1 is that nano zinc oxide is replaced with an equal amount of nano magnesium oxide.

[0057] The only difference between surface glaze formulation 14 and surface glaze formulation 1 is that nano alumina, nano silica, and nano zinc oxide are replaced with equal amounts of micron-sized alumina, micron-sized silica, and micron-sized zinc oxide, respectively.

[0058] Among them, the particle size of nano-alumina is 20-50 nm;

[0059] The particle size of nano-silica is 50-100 nm;

[0060] The particle size of nano zinc oxide is 80-120 nm.

[0061] The particle size of nano-magnesium oxide is 100-300 nm;

[0062] The particle size of micron-sized alumina is 40-80 μm;

[0063] Micron-sized silica has a particle size of 50-100 μm;

[0064] The particle size of micron-sized zinc oxide is 50-100 μm;

[0065] Nano-alumina and micron-sized alumina, nano-silica and micron-sized silica, and nano-zinc oxide and micron-sized zinc oxide are all selected from the same manufacturer's system products.

[0066] Polyacrylate microspheres were purchased from Cospheric (PMMA) with a particle size of 250-300 nm.

[0067] The matte frit is composed of the following components in weight percentage: 21.33% Al2O3, 43.84% SiO2, 3.61% K2O, 3.36% Na2O, 9.08% BaO, 4.87% SrO, 6.53% ZnO, 3.52% CaO, and 3.86% MgO.

[0068] The formulations of the base glaze and the surface glaze of the antique ceramic tiles in Examples 1-10 and Comparative Examples 1-13 are as follows:

[0069] Example 1 uses base glaze formulation 1 and surface glaze formulation 1;

[0070] Example 2 uses base glaze formulation 2 and surface glaze formulation 1;

[0071] Example 3 uses base glaze formulation 3 and surface glaze formulation 1;

[0072] Example 4 uses base glaze formulation 4 and surface glaze formulation 1;

[0073] Example 5 uses base glaze formulation 5 and surface glaze formulation 1;

[0074] Example 6 uses base glaze formulation 1 and surface glaze formulation 2;

[0075] Example 7 uses base glaze formulation 1 and surface glaze formulation 3;

[0076] Example 8 uses base glaze formulation 1 and surface glaze formulation 4;

[0077] Example 9 uses base glaze formulation 1 and surface glaze formulation 5;

[0078] Example 10 uses base glaze formulation 1 and surface glaze formulation 6;

[0079] Comparative Example 1 uses base glaze formulation 6 and surface glaze formulation 1;

[0080] Comparative Example 2 uses base glaze formulation 7 and surface glaze formulation 1;

[0081] Comparative Example 3 uses base glaze formulation 8 and surface glaze formulation 1;

[0082] Comparative Example 4 uses base glaze formulation 9 and surface glaze formulation 1;

[0083] Comparative Example 5 uses base glaze formulation 10 and surface glaze formulation 1;

[0084] Comparative Example 6 uses base glaze formulation 1 and surface glaze formulation 7;

[0085] Comparative Example 7 uses base glaze formulation 1 and surface glaze formulation 8;

[0086] Comparative Example 8 uses base glaze formulation 1 and surface glaze formulation 9;

[0087] Comparative Example 9 uses base glaze formulation 1 and surface glaze formulation 10;

[0088] Comparative Example 10 uses base glaze formulation 1 and surface glaze formulation 11;

[0089] Comparative Example 11 uses base glaze formulation 1 and surface glaze formulation 12;

[0090] Comparative Example 12 uses base glaze formulation 1 and surface glaze formulation 13;

[0091] Comparative Example 13 uses base glaze formulation 1 and surface glaze formulation 14.

[0092] Table 1

[0093]

[0094] Table 2

[0095]

[0096] Example of effect

[0097] To investigate the application performance of the antique ceramic tiles provided by this invention, the antique ceramic tiles in the embodiments and comparative examples were subjected to the following tests:

[0098] (1) Gloss: The WGG60-E4 photometer was used, referring to GB / T 13891-2008 "Method for Determination of Specular Gloss of Building Facing Materials";

[0099] (2) Stain resistance: Refer to Appendix G of GB / T 4100-2015 "Ceramic Tiles", dry-pressed ceramic tiles (E≤0.5%Bia class);

[0100] (3) Stain resistance and durability: Refer to Appendix G of GB / T 4100-2015 "Ceramic Tiles" for the requirements of stain resistance for dry-pressed ceramic tiles (E≤0.5%Bia class). After grinding for 1500 revolutions, the stain resistance is tested. The stain resistance and durability are defined as qualified if the stain level is ≥3.

[0101] (4) Abrasion resistance: Refer to Appendix G of GB / T 4100-2015 "Ceramic Tiles", dry-pressed ceramic tiles (E≤0.5%Bia class);

[0102] (5) Acid and alkali resistance: GB / T 4100-2015 "Ceramic Tiles" Appendix G, Dry-pressed ceramic tiles (E≤0.5%Bia class);

[0103] (6) Surface roughness: Ra value was obtained by testing according to GB / T 1031-2009.

[0104] The test results are shown in Table 3.

[0105] Table 3

[0106]

[0107] As shown in Table 3:

[0108] Compared with the comparative example, the antique ceramic tile provided by this invention has a lower gloss, while maintaining low surface roughness and excellent wear resistance and stain resistance. The gloss of the antique ceramic tile provided by this invention is below 3°, and under natural light, the surface is basically without glare, without being dazzling or causing dizziness, thus achieving an elegant and antique decorative effect. Its surface roughness is less than 1.5 μm, maintaining a delicate and smooth texture, without being rough or dry, and with an overall warm and smooth feel. It has excellent stain resistance and good stain resistance durability, achieving a self-cleaning stain-resistant effect during long-term use. Furthermore, it has superior wear resistance and acid and alkali resistance, exhibiting good durability and practicality.

[0109] In summary, the antique-style ceramic tiles provided by this invention optimize the raw material composition and formula of the base glaze and surface glaze layers, and construct a wear-resistant, stain-resistant, and self-cleaning composite framework in the surface glaze layer. This achieves a gloss level of less than 2°, resulting in a surface with virtually no glare visible to the naked eye under illumination, avoiding glare and dizziness, and achieving an elegant, antique decorative effect. Simultaneously, it maintains a low surface roughness, providing a smooth and delicate texture. Further adjustments to the formula achieve excellent and durable stain resistance, wear resistance, and acid and alkali resistance, solving the problems of excessively high gloss in existing antique-style ceramic tiles and the inability of low-gloss tiles to simultaneously achieve stain resistance and wear resistance. With a good balance of various properties, it can be widely applied in the field of architectural ceramics technology.

[0110] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. An antique ceramic tile, characterized by, The body layer, the bottom glaze layer, the pattern layer, the functional ink layer and the surface glaze layer are sequentially arranged. The preparation raw materials of the bottom glaze layer include the following components in parts by weight: air knife clay 4-10 parts, calcined kaolin 12-18 parts, wollastonite 3-6 parts, strontium carbonate 7-11 parts, zirconium silicate 6-12 parts, nano-alumina 3-6 parts, potassium feldspar 22-30 parts, and sodium feldspar 25-30 parts. The preparation raw materials of the surface glaze layer include the following components in parts by weight: calcined kaolin 7.5-12.5 parts, air knife clay 4-8 parts, nano-alumina 4-9 parts, wollastonite 8-12 parts, matt frit 20-30 parts, nano-silicon dioxide 1-5 parts, nano-zinc oxide 2-6 parts, talc powder 4-8 parts, polyacrylate microspheres 2-6 parts, potassium feldspar 10-17 parts, and sodium feldspar 8-16 parts.

2. The ceramic tile according to claim 1, characterized in that, The nano-alumina has a particle size of 20-50 nm.

3. The ceramic tile according to claim 1, wherein The nano-silicon dioxide has a particle size of 50-100 nm.

4. The ceramic tile according to claim 1, wherein The nano-zinc oxide has a particle size of 80-120 nm.

5. The ceramic tile according to claim 1, wherein The polyacrylate microspheres have a particle size of 250-350 μm.

6. The ceramic tile according to claim 1, wherein The preparation raw materials of the bottom glaze layer include the following components in parts by weight: air knife clay 6-8 parts, calcined kaolin 14-16 parts, wollastonite 4-5 parts, strontium carbonate 8-10 parts, zirconium silicate 6-7 parts, nano-alumina 4-5 parts, potassium feldspar 24-26 parts, and sodium feldspar 27-29 parts.

7. The ceramic tile according to claim 1, wherein The preparation raw materials of the surface glaze layer include the following components in parts by weight: calcined kaolin 9-11 parts, air knife clay 5-7 parts, nano-alumina 5.5-7.5 parts, wollastonite 9-11 parts, matt frit 24-26 parts, nano-silicon dioxide 2-4 parts, nano-zinc oxide 3-5 parts, talc powder 5-7 parts, polyacrylate microspheres 3-5 parts, potassium feldspar 13-14 parts, and sodium feldspar 11-13 parts.

8. The ceramic tile according to claim 1, wherein In the preparation raw materials of the surface glaze layer, the mass ratio of the nano-alumina to the nano-zinc oxide is (6.2-6.8):(3.7-4.3).

9. The ceramic tile according to claim 1, wherein In the preparation raw materials of the surface glaze layer, the mass ratio of the nano-silicon dioxide to the polyacrylate microspheres is (2.8-3.2):(3.6-4.4).

10. The ceramic tile according to claim 1, wherein The matt frit includes the following components in mass percentage: 17.52-22.54 % Al2O3, 41.02-46.65 % SiO2, 1.57-5.65 % K2O, 1.25-4.87 % Na2O, 6.58-11.57 % BaO, 2.14-7.59 % SrO, 3.54-9.52 % ZnO, 1.36-5.68 % CaO, and 1.05-6.67 % MgO.

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