Iron oxide red pigments are introduced mainly in the form of colorants in ceramic pigment formulations. So how does it apply in various colors? Today by the experts of the divine pigment for everyone to analyze it ~ ~
Colored cement bricks such as ceramic glazed tiles are used in large quantities of iron oxide red raw materials. Therefore, the amount of iron oxide red pigment in ceramic pigments is large, and it is estimated that the annual dosage is more than 10,000 tons. At present, the production method of iron oxide red pigment used in ceramic pigments is mainly divided into sulfuric acid method and mixed acid method (nitric acid method), and the iron oxide red pigment with bright red appearance is obtained after processing and processing with thin iron plate as raw material.
First, the application of iron oxide red in the brown series
Among the pigments used in ceramic glazes, the brown series pigments occupy a large market. Especially in the production of porcelain pieces and vintage tiles, the two series of golden and red brown are used extensively.
The brown series is mainly Fe-Cr-Zn-Al and Fe-Cr-Zn two crystal structures, and iron oxide red pigments are mainly added in the form of colorants. Trivalent iron ions remain red, colored by a complex of chrome green, producing a hue ranging from golden to black brown. This study did the following experiments: the use of chemical composition of the frit, to the frit to add 3% of the pigment, with the increase of iron oxide red pigment in the formula, the redness value and yellowness value are correspondingly reduced, the color of the pigment from golden yellow tone to reddish brown tone change, the brightness value of the pigment is also correspondingly reduced; at the same time, the experiment found that the glaze pinhole also increased accordingly.
This is due to the increase of iron oxide red pigment in the formula, the unsaturated iron ions in the pigment increase, which are easily separated from the high temperature liquid phase of the frit glaze, and the color saturation decreases accordingly while the pinhole increases. From the appearance of the pigment, with the increase of the content of iron red pigments, the degree of sintering of the pigments increases, indicating that iron red pigments have the effect of reducing the firing temperature in brown series products.
Second, the application of iron oxide red in the blank black material
In the production of ceramic wall and floor tiles, the main use of black, yellow, coffee three medium tones, of which ceramic body black material accounts for more than 35% of the body color, manufacturers consume more than 60,000 tons of body black material every year. Iron oxide red pigment is the main raw material for the formulation of blank black material, and the content can usually reach 50% to 80%. The color color of iron oxide red products produced by different manufacturers varies greatly.
Third, the application of iron oxide red in glazed black material
Black pigments for glaze cost more than other glaze pigments, with cobalt black pigments preferring the hue for pure blues. Because the black pigment does not contain cobalt oxide, the cost is slightly lower than that of cobalt black. However, there are some bright black products on the market, and their pure black tones are comparable to cobalt black. Iron oxide red pigments mainly play a role in color aiding in glazed black materials. It is generally believed that under the conditions of oxidation atmosphere, the NiO-Cr2O3 blue-green tone formed at 1000 °C, the NiO-Fe2O3 black with red tone, and the Co-Fe2O3 bluish black tone, through the composite coloring and present a purer black. At the same time, CuO-Fe2O3 can also show a blue-black hue in the glaze.
Since iron red has a greater influence on the firing temperature and hue, when selecting iron red for the production of black material for ceramic glaze, it is necessary to select according to the design requirements and test whether it meets the requirements through the calcination production formula.
Today for the application of iron oxide red in ceramic colors, the experts of Shencai pigments will share so much with you, and more professional content is looking forward to ~