The tinting process for water-based wall paint requires a balance between color accuracy and stability, necessitating comprehensive management across the entire chain, from raw material selection and tinting techniques to application control. Firstly, the compatibility between the colorant and the base paint is the core factor determining color accuracy. Water-based colorants are broadly classified into inorganic and organic types. Inorganic colorants are primarily iron oxide-based, offering excellent weather resistance but lower color saturation; organic colorants, on the other hand, boast vibrant colors but inconsistent lightfastness. When tinting, priority should be given to colorants compatible with the base paint's resin system. For example, acrylic base paints require the same type of colorant to avoid uneven pigment dispersion due to differences in resin molecular structures. Simultaneously, the colorant concentration must be adjusted according to the base paint's viscosity. Excessive concentration can lead to sedimentation, while insufficient concentration necessitates increasing the amount added, resulting in decreased film gloss.
The standardization of the tinting process directly impacts color stability. In practice, the principle of "primary colors first, secondary colors later; light colors to dark colors" should be followed. This means adding the primary color (e.g., white, yellow) first, using a large quantity and having weak tinting strength, then gradually adding the darker colors (e.g., black, red). Each addition should not exceed 5% of the total amount, and continuous stirring is necessary to ensure thorough dispersion of the pigments. During this process, a standard color chart or spectrophotometer should be used for real-time comparison to avoid deviations caused by differences in human color sensitivity. For mixing multi-color paints, special attention must be paid to the "floating" phenomenon of pigments. For example, the density difference between yellow and blue pigments in green wall paint may cause layering. In this case, 0.1%-0.5% of a leveling agent or anti-floating agent can be added to reduce surface tension and ensure uniform pigment suspension.
Controlling the construction environment is crucial for ensuring color stability. Temperature and humidity significantly affect the drying speed of the paint and the orientation of the pigments. Excessive temperature accelerates solvent evaporation, leading to uneven surface tension and color spots; excessive humidity may cause water-based paints to absorb moisture, resulting in whitening. Therefore, the ambient temperature during construction should be controlled between 15-35℃, and the relative humidity should not exceed 85%. Furthermore, substrate preparation is crucial for color rendering. Differences in substrate surface roughness can lead to uneven paint absorption. For example, wooden substrates need to be sanded to at least 600 grit, and metal substrates require rust prevention treatment and the application of an adhesion promoter to ensure uniform coating thickness.
Dry-wet film color differences are a common challenge in color matching. Water-based paints are typically lighter in color when wet due to their higher light refractive index. After drying, the pigment particles are more tightly packed, causing the color to deepen by 10%-20%. To address this, adjustment margins should be allowed during color matching. For example, if the target color is dark gray, it can be adjusted to medium gray in the wet film state, achieving the desired effect after drying. Simultaneously, the sample color matching process should simulate actual construction conditions. Samples should be applied using the same tools as the wall surface (such as rollers or spray guns), and compared with a standard color card after complete drying to avoid misjudgment due to differences in film thickness.
Batch consistency control is a core requirement of industrialized production. Different batches of base wall paint may exhibit color variations due to differences in raw materials. Therefore, a strict raw material inspection system is necessary, requiring colorimetric testing of each batch of resin and filler to ensure a ΔE value (color difference unit) of less than 1.5. Automated metering equipment should be used during production to avoid human weighing errors, and each batch of paint should be sampled and retained for at least three months for traceability. For large-scale projects, it is recommended to prepare the required amount in one batch to avoid color differences caused by batch mixing.
The impact of auxiliary materials is often overlooked but crucial. Additives such as driers and hardeners may alter the hue of the paint due to their own color or chemical reactions. For example, some amine hardeners can neutralize acidic pigments, causing the color to darken. Therefore, colorless or light-colored auxiliary materials should be selected when tinting, and a margin for adjustment should be reserved in the formulation. Furthermore, the choice of thinner must be compatible with the solvent system. For example, alcohol-based thinners are suitable for acrylic paints, while ester-based thinners may cause yellowing of the paint film.
Long-term stability maintenance requires attention to storage and transportation. Water-based paints may separate during storage due to pigment sedimentation, therefore regular stirring and avoidance of violent vibration are necessary. During transportation, temperatures should be protected from excessively high (above 40°C) or excessively low (below 5°C) temperatures; the former may cause resin cross-linking, and the latter may cause pigment precipitation. For pre-mixed colored paints, it is recommended that the storage time not exceed 3 months. Before use, the paint should be stirred again and filtered to ensure uniform color and no impurities. Through meticulous control throughout the entire process, the accuracy and stability of water-based wall paint colors can be maximized.
