Getting started with color mixing techniques and color paste selection
Water-based color paste refers to a stable pigment suspension formed by dispersing organic and inorganic pigments and surfactants in an aqueous medium and pulverizing them.
Inorganic color paste: Most of them are iron oxide-based; acid and alkali resistance, weather resistance, light resistance, etc. are relatively excellent. For example: Y42 iron yellow, iron black, R101Y/R101V iron red
Organic color paste: organic synthesis; the unit price of color paste is relatively high, and some color pastes have low light resistance and weather resistance; use according to order requirements; pay attention to the selection of color paste. Y74\83 and R112 are not recommended to be used on exterior walls; they can only be used on exterior walls when the amount of color paste added reaches 4%. For specific applications, please consult the technical department immediately.
For example: R254/112 bright red, O73 orange, BK7/6800HT carbon black, Y74\154\83\110 yellow, B153 phthalocyanine blue, G7 phthalocyanine green, V23 purple, R122 rose red, titanium white (titanium white color reducing power strong, covering effect)
Precautions for color application:
① Under the condition of ensuring the hiding power, try to reduce the cost. That is to reduce the amount of color paste, but can not reduce the amount of color paste without limit
l If the color paint contrast ratio is greater than 0.95, it can generally be judged that the hiding power is qualified
l The construction test should be carried out for darker bright colored paints: there is little difference in the color of the dry film after two coats and three coats (judging by experience). It is not included in the quality inspection assessment; but it can be used as a reference.
② Avoid paint disease caused by floating color and blooming (consider the content of emulsion and titanium dioxide)
Finger grinding method: Take 100 grams of white paint, add 2-3 grams of color paste to be tested, stir well, and apply it on the surface of the object to be coated. After penetrating, observe whether there is a color difference between the place rubbed with your fingers and the place that has not been rubbed. If the difference is large, the compatibility of the color paste with the tested paint is not good, and the paint prepared with this color paste is easy to produce Floating color phenomenon. If the color is the same, generally there will be no floating color phenomenon.
Color system: 1. Iron oxide system 2. Blue gray system 3. Warm color system
Light color: the total amount of color paste is less than 1%, and the black paste is less than 0.5%
Medium dark color: the amount of color paste used is between 1% and 3%
Dark color: more than 3% (covering ability reaches more than 95%)
Note: Determine the main color, but it does not mean that the main color colorant is added more. Consider the inorganic class first, then the organic class.
When mixing dark paint, the amount of titanium dioxide should be reduced to reduce the decolorizing power and improve the tinting power. When tinting extremely dark colors, use a white paint with close to “0” TiO2 content. For particularly bright and bright colors, use a lot of emulsion.
There are many types of colorants to choose from, and the color that is adjusted is gray and dark. On the contrary, there are fewer types of color pastes, and the colors that are adjusted are brighter and more saturated.
1. Tinting strength of color paste (tinting power)
Tinting strength is an important index, which reflects the color concentration, color development performance and flocculation of pigment dispersion of color paste. The data is measured by the number of parts of pigment slurry required for the color to reach 1/25 of the International Standard Depth (ISD), the smaller the value, the higher the tinting strength. The value represents the number of grams of color paste that needs to be added to the white base paint: in latex paint—the white base paint has a titanium dioxide content of 25% (1/25ST)
2. Compatibility of color paste (color development performance – finger research method)
The compatibility of the color paste and the application system is the key to affect the color floating, flocculation and some surface defects of the paint film. If the fineness of the color paste is not enough, poor dispersion performance will lead to poor color development of the color paste, which will affect the reproducibility of the paint.
3. Dispersion performance of color paste (degree of flocculation)
The dispersion performance of the color paste is not good, and the migration difference between the pigment flocs in the color paste and the white pigment and filler particles in the base material is relatively easy to reflect. This difference often makes the pigment flocs no longer evenly distributed. Small differences in temperature, density and surface tension exist inside the film, the pigment flocs and paint base naturally participate in this movement, and the pigment flocs separate, resulting in floating and blooming. If the dispersion performance of the color paste is good, the generation of floating color and blooming can be avoided.
4. Light resistance and weather resistance of color paste
Light fastness: grade 1 is the worst, grade 8 is the best
Weather resistance: grade 1 is the worst, grade 5 is the best
5. Pigment content of the color paste
The tinting strength of the color paste is not directly proportional to the pigment content. Same pigment content. The tinting strength of different fineness is also very different.
6. Fineness of color paste
The fineness is an intuitive indicator reflecting the color dispersion effect and storage stability of the color paste. Generally, for the same pigment paste, the smaller the particle size, the larger the specific surface area, and thus the larger the hiding power, and the higher the tinting strength; the smaller the fineness, the higher the gloss, and the better the dispersion effect and storage stability. the better. Of course, the fineness of the color paste is not as fine as possible, because when the particle becomes smaller and its specific surface area increases, the absorbed light energy increases and the degree of damage increases, resulting in a decrease in its weather resistance; and the particle size is too large When the paint film is dry, with the precipitation of water, the color paste migrates to the surface together, which may easily cause inaccurate color matching and wall color difference.
7. Acid and alkali resistance of color paste
8. The following factors must be considered for external use: a. light and weather resistance; b. acid and alkali resistance; c. compatibility with the use system; d. coloring strength, hiding power and color development; Quality inspection matching; f. Storage stability of color paste
