An Introduction To Color Paste Performance Indicators, You Shouldn’t Miss It!

1. Tinting strength of color paste (tinting power)
For the comparison of water-based color pastes, tinting strength is an important indicator, which reflects the color concentration, color development performance and pigment dispersion flocculation of the color paste. Data are measured as the number of parts of pigment slurry required to achieve 1/25 of the International Standard Depth (ISD) of the color, with the smaller the number, the higher the tinting power. The numerical value represents the grams of color paste required to be added to the white base paint: In latex paint - the titanium dioxide content of the white base paint is 25% (1/25ST).

2. Compatibility of color paste (color development performance - finger grinding method)
The compatibility of the color paste and the system used is the key to affecting the floating, flocculation and surface defects of some paint films. Before using color paste for color matching, be sure to do a compatibility test. Additives can often be used to solve the compatibility problem between color paste and paint. Add the color paste to the white paint, usually into a medium or light color, and apply it on the surface of the object to be coated or the surface of the imitation object to be coated. When it is about to solidify, grind the surface part of the coating with your fingers. After it dries, observe whether there is any obvious color difference. (Visual inspection). If the fineness of the color paste is not enough and the dispersion performance is poor, the color development of the color paste will be poor, which will affect the reproducibility of the paint.

3. Dispersion performance of color paste (degree of flocculation)
The degree of deflocculation of pigment particles by additives determines the size and stability of the color paste dispersion. Generally speaking, it is impossible to achieve complete deflocculation (that is, the pigments exist uniformly and stably in the system as primary particles), and they are only uniformly distributed in the system in the form of agglomerates of pigment particles. A good color paste has a very high degree of deflocculation, that is to say, the agglomerates are as small as possible, so that it has good tinting power, excellent color development and storage stability. Due to the poor dispersion performance of the color paste, 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 be reflected. This difference often makes the pigment flocs no longer evenly distributed and becomes a film due to Due to the small differences in temperature, density and surface tension within the paint film, the pigment flocs and paint base naturally participate in this movement, and the pigment flocs separate, resulting in floating colors and blooming. If the dispersion performance of the color paste is good, floating color and blooming can be avoided. In addition, the dispersion of the paint itself also directly affects the floating color and blooming of the paint.

4. One of the structural properties of color paste (light resistance, weather resistance)
The light and weather resistance of color pastes is tested through outdoor exposure, but the actual outdoor exposure time is too long. Generally, color paste performance testing is mostly done through simulation tests of instruments and equipment.
Lightfastness: Use outdoor acrylic latex paint to make 1/3ISD and 1/25ISD standard color swatches for exposure. Use xenon light source (1000W) to expose for 72 hours, use a 1-8 grade blue wool ruler to expose at the same time as the standard color sample, and get the color difference to grade, grade 1 is the worst, grade 8 is the best, (has been evaluated by color measurement software )
Weathering: Use outdoor acrylic latex paint in 1/3ISD and 1/25ISD standard color swatches for exposure. The ATLAS artificial aging instrument was used for 500 hours of exposure, and the ISD gray card was used for color difference rating, with level 1 being the worst and level 5 being the best. (Evaluated by color measurement software)

5. Pigment content of color paste
The pigment content is for reference only and cannot be used as an indicator to evaluate the performance of the color paste. The tinting power of the color paste is not simply proportional to the pigment content. The same pigment content has great differences in tinting strength with different fineness. In order to ensure the stability of the tinting strength of the color paste, the pigment content of the color paste changes within a certain range. The value provided in the color paste data is a typical reference value.

6. Fineness of color paste
Fineness is an intuitive indicator that reflects the coloring power dispersion effect and storage stability of the color paste. Generally speaking, for the same pigment paste, the smaller the particle size, the greater the specific surface area, thus increasing the covering ability and the higher the tinting power; the smaller the fineness, the higher the gloss, and the dispersion effect and storage stability are poor. The better. Of course, the fineness of the color paste is not as fine as possible, because when the particles become smaller and their specific surface area increases, the absorbed light energy increases and the degree of damage also increases, resulting in a decrease in weather resistance; and the particle size is too large When the paint film forms and dries, as the water precipitates, the color paste migrates to the surface, which can easily lead to inaccurate color matching and color differences on the wall.

7. Compatibility of color paste and paint
Use the finger grinding method to take 100 grams of white paint, add 2-3 grams of the color paste to be tested, mix thoroughly, and apply it on the surface of the object to be coated. When it is about to solidify, use your fingers to grind the surface part of the coating film until the paint film is completely dry. Finally, observe whether there is a color difference between the areas that have been rubbed with your fingers and those that have not been rubbed. If the difference is large, the compatibility between the color paste and the paint being tested is not good, and the paint prepared with this color paste is prone to floating. color phenomenon. If the colors are the same, there will generally be no floating color phenomenon.

8. Structural properties of color paste 2 (resistance to chemical media)
The chemical media resistance of water-based colorants is mainly acid and alkali resistance, that is, chemical migration resistance. This performance is essentially dependent on the pigment itself and must be taken into account in colorants for outdoor use. Generally, water-based coatings also require acid and alkali resistance, but do not require resistance to organic solvents and other chemicals. Acid resistance and alkali resistance: According to the DIN16524 standard, the color paste is dried (105°C) and placed in 1% sulfuric acid and 2.5% sodium hydroxide solution for 24 hours, then taken out and washed to measure its acid and alkali resistance. . Based on bleeding and color changes, it is evaluated according to the 5-level standard. Level 5 indicates excellent acid and alkali resistance, and level 1 indicates extremely poor acid and alkali resistance.

9. Other physical and chemical parameters of color paste
(density, viscosity, pH value, pigment content, solid content, fineness and gloss)
Density: The unit is grams/cubic centimeter, and the measurement method is in accordance with the provisions of GB/T1756.
Viscosity: an important indicator reflecting the storage stability of color paste. (STM-Ⅲ Stormer Viscometer)
PH value: PHB-2 portable pH meter measures the pH value (PH value) of water-based high-quality color paste systems, which is generally between 7-10. Therefore, the color retention and tinting strength of color pastes in coating systems with a pH value of 7-10 Excellent color development and other properties.
Fineness and gloss: an intuitive indicator reflecting the dispersion effect and storage stability of the color paste. Generally speaking, for the same pigment paste, the smaller the fineness, the higher the gloss, and the better the dispersion effect and storage stability.

10. Quality stability of color paste
Generally, the consistency of the solid content, fineness, viscosity, tinting strength, color development, light and weather resistance, etc. of the color paste is ensured through strict control of the production formula - raw materials - production process - finished product. (Evaluate using color matching software, Lab value and color difference control DE < 1.0)
Generally, the storage stability of water-based color pastes does not show obvious defects such as delamination, agglomeration, coarsening, and precipitation when stored at room temperature of about 25°C for one year, and the tinting strength, color development, and other physical and chemical properties do not decrease significantly. Generally, aging determination can be accelerated through thermal storage and freezing experiments, and evaluation can be done through can opening effect evaluation and color matching software.