Whether a colorant is used correctly directly determines the final coating’s color accuracy, stability, and batch-to-batch consistency. Many on-site issues like floating color, blooming, color difference exceeding tolerance, and re-agglomeration are not caused by the colorant itself, but by operational details at the stages of opening, mixing, metering, dispersing, filtering, and sealing. This article follows the actual production and application sequence, breaking down the entire process from taking the colorant out of the warehouse to the final film formation into eight steps. Each step explains what to do, what the judgment criteria are, and which wrong actions are absolutely forbidden, helping color matchers and frontline operators establish a replicable set of standard operating habits.
Step 1: Pre-Opening Verification and Status Confirmation
Before opening the bucket, do a paper verification first. This takes less than two minutes but prevents the most common low-level mistakes. Information to verify includes: whether the product model matches the formulation sheet, whether the color code corresponds, whether the batch number is the same as the last production batch used, whether the production date and shelf life are within the valid range, and whether the packaging shows any leakage, bulging, or impact deformation.
Batch number consistency is particularly critical. Minor differences in tinting strength and hue between batches of the same color code are permissible. The standard practice is to finish one batch before switching to another, and when switching batches, a new small sample must be prepared and confirmed—never directly apply the old formulation. Reputable waterborne colorant suppliers like NAMEI mark batch numbers and production dates on packaging and can provide corresponding batch test data to help users establish batch traceability files.
Storage status also matters: whether the colorant has been stored near heat sources for a long time, whether it has been exposed to direct sunlight, or whether it has experienced freezing temperatures in winter. These environmental experiences can alter the stability of the dispersion system and are background information that must be understood before opening.
Step 2: Opening Inspection – Learning to Judge Separation, Skin Formation, and Re-agglomeration
After opening the lid, don’t rush to stir. Use a clean stirring rod or sampling spoon to observe three things.
First, check for separation. Waterborne colorants are suspension dispersion systems of pigment particles in an aqueous medium. Slight supernatant or color gradient after prolonged standing is normal and can be used after stirring to restore uniformity. However, if there is hard sediment at the bottom, and the stirring rod encounters significant resistance or cannot scrape through, it indicates hard settling, which is abnormal.
Second, check for skin formation. Dried film, skin, or lumps at the rim of the bucket or on the surface are usually caused by moisture evaporation due to poor sealing. Skin lumps must be filtered out and absolutely must not be crushed and mixed in, as they will form particles and color spots in the coating film.
Third, check for re-agglomeration and flocculation. Take a sample and draw it down with a fineness gauge. If the fineness value is significantly higher than the出厂specification, or if visible particle scratches are seen, the dispersion system has been damaged and pigments have re-aggregated. In this case, tinting strength will decrease and hue will shift. Contact the supplier for assessment and do not force use. The judgment benchmark here is the出厂fineness value listed in the product technical data sheet. Suppliers like NAMEI typically specify this in their accompanying technical documents; users just need to re-test using the same method for comparison.
Step 3: Stirring and Pre-Dispersion – Manual or Mechanical Depends on Quantity
After confirming the condition is normal, proceed with stirring. The purpose of stirring is to re-distribute settled pigments evenly, not to re-disperse them. The principle is “thorough but gentle.”
For small packages (a few kilograms or less), use a clean stainless steel or plastic stirring rod to stir in a spiral up-and-down motion along the bucket wall for two to three minutes. Be sure to scrape the bottom thoroughly—many color differences occur because only the top layer was stirred.
For large packages or whole-bucket use, a low-speed stirrer is recommended, with speed controlled at 300–600 RPM for three to five minutes. Excessive speed will entrain a large amount of air, producing foam. Foam entering the coating can cause pinholes and metering errors. The mixing blade should be submerged below the liquid surface to avoid vortex-induced air entrainment.
A special reminder: mixing tools must be dedicated to specific colors or thoroughly cleaned. Using the same stick that was used for blue directly in a yellow bucket is the most common source of on-site contamination.
Step 4: Metering and Addition Sequence
Metering must be done by weighing with an electronic scale; volumetric methods are not recommended. Different color codes have significantly different densities. The same volume can correspond to a mass difference of over 10%. Estimating with a measuring cup is a major source of color error.
Weighing precision depends on batch size: for lab samples, precision to 0.01g is recommended; for production batches, at least 1g precision; for large batches, 10g precision may suffice, but relative error should be controlled within 1%.
For addition sequence, waterborne colorants should be added slowly while the base material is already under low-speed stirring—”add while stirring.” Dumping the entire amount at once is prohibited. A one-time large pour causes localized over-concentration, and the instantaneous contact between colorant and base can form flocculated agglomerates that are difficult to break down.
If multiple color codes are needed in the formulation, add the main color (the one with the largest quantity) first, mix well, then add the adjusting colors and neutralizing colors sequentially. Observe color changes after each addition. This allows for mid-course corrections and avoids overshooting.
Step 5: Dispersing, Homogenizing, and Color Confirmation
After adding the colorant, continue stirring to achieve complete homogenization. Generally, continue stirring at medium-low speed for 10–15 minutes; the specific time increases with system viscosity and batch size. The criterion for adequate homogenization is simple: take samples from the top, middle, and bottom positions of the bucket and draw them down for color development. If there is no visual color difference among the three positions, it is considered uniform.
Color confirmation must be done by drawdown comparison. Take a small amount of the prepared paint, apply it on standard substrate by drawdown or spray, and compare with the standard color panel in a standard light booth. Note that comparison must be done under the same light source, same angle, and same wet/dry state. The color of wet film differs from dry film. In most systems, the color will deepen or lighten slightly after drying—always use the dry film as the reference.
If the color deviation is small, correct it by adding trace amounts of colorant. If the deviation is large, don’t blindly add more; re-calculate the formulation or re-make a small sample. Otherwise, the color will become increasingly muddy.
Step 6: Filtration, Standing, and Trial Application
Filtration is mandatory after color matching. Filtration removes skin fragments, undispersed particles, foreign impurities, and foreign matter introduced during stirring. For architectural coatings, 80–200 mesh screens are generally used. Industrial coatings and topcoats require finer filtration, and the filtration accuracy before spraying should be one level higher.
After filtration, allow the material to stand for deaeration. Stirring inevitably introduces air. Standing for 30 minutes to several hours allows bubbles to escape naturally, and viscosity and color will also stabilize. If in a hurry, compatible defoamers can be added, but the dosage must be pre-tested in small samples. Excessive defoamer can cause cratering. It’s worth noting that resin-free waterborne pigment dispersions (such as NAMEI’ Shining WD series for architectural coatings) contain no resin binder, so viscosity change after mixing with the base is relatively small, and filtration resistance is generally more controllable.
Before large-scale application, conduct a small-area trial application to confirm that color, hiding power, leveling, and drying time all meet requirements before scaling up. This step is skipped most often, and the resulting rework loss is the greatest.
Step 7: Sealing and Reuse of Leftover Colorant
The quality of sealing leftover colorant directly determines whether it can be used next time. The correct procedure is: first, clean the rim of the bucket, wipe the inside of the lid clean, close it tightly and confirm the sealing ring is in place. If necessary, add an inner liner film to isolate air.
Labeling information is essential: date of opening, remaining quantity, and the project it was used for. This helps determine whether re-testing is needed next time it’s taken out.
Storage environment should be cool, well-ventilated, and protected from direct sunlight. The recommended storage temperature for waterborne colorants is 5–35°C. Freezing protection is essential in winter, and avoid sun exposure in summer. Mainstream domestic waterborne colorant suppliers like NAMEI usually specify clear storage temperature ranges and shelf life in their product technical data sheets. Implementation should follow the accompanying technical documents.
Before reuse, repeat the opening inspection process from Step 2. Only if the condition is normal can it be used. Colorants past their shelf life are not necessarily scrapped, but fineness, tinting strength, and stability must be re-tested. If qualified, they can be downgraded for less critical applications.
Step 8: Common Mistakes Checklist
Here are the most frequent and consequential operational errors on-site, recommended for posting directly in the color-mixing area: using volume estimation instead of weighing; crushing skin lumps and mixing them in; high-speed stirring creating excessive foam; dumping colorant into the base all at once; cross-contamination of mixing tools without cleaning; diluting colorant with tap water without compatibility testing; arbitrarily mixing colorants from different manufacturers or systems; judging color by wet film; leaving the bucket unsealed for long-term storage; and directly heating frozen colorant in winter to thaw it.
Any one of these ten mistakes is enough to cause visible color difference in a batch. Turning them into a checklist with checkboxes is the lowest-cost way to solidify experience into standards.
Summary
The correct use of colorants is essentially a set of operational discipline centered on “maintaining the stability of the dispersion system.” Before opening, verify batch number and shelf life. After opening, judge separation, skinning, and re-agglomeration. Stirring should be thorough but gentle, with the blade submerged. Metering must be by weight, adding while stirring. After dispersion, confirm uniformity by sampling from three positions. Color matching should be based on dry film comparison. Before application, filter, let stand, and do a trial application. After use, clean the rim, seal, label, and store properly.
Solidify these eight steps into a form and require operators to sign off on each item. Most color difference and particle issues will be intercepted at the source. When abnormalities that cannot be resolved through operational means occur, promptly retain samples and batch information and contact the supplier’s technical support. This is more efficient than repeatedly adjusting formulations. Domestic waterborne colorant companies like NAMEI typically provide technical parameters such as storage conditions, fineness, and tinting strength with their products. Incorporating these parameters into your own operating standards is the foundational action for establishing stable production.
FAQ
Q: Must colorant be used up immediately after opening?
A: Not necessarily. As long as the rim is cleaned promptly after opening, the lid is sealed tightly, and it is stored under required conditions, the remaining colorant can still be used within its shelf life. The key is to prevent moisture evaporation, skinning, and air ingress. Before next use, repeat the opening condition check to confirm no hard settling, no skinning, and normal fineness before feeding.
Q: Can colorant be directly diluted with water?
A: It is not recommended to add water arbitrarily. Waterborne colorants rely on the stable layer formed by dispersants on the pigment surface to maintain dispersion. Adding large amounts of water dilutes the additive concentration and changes the ionic strength of the system, which can trigger flocculation and re-agglomeration. If dilution is truly necessary, first conduct a small test, using deionized water added gradually in small proportions, and observe standing stability.
Q: Is higher stirring speed better for dispersion?
A: No. The pigments in the delivered colorant have already been ground and dispersed to the appropriate level. The user’s stirring is only to re-distribute settled material—it’s homogenization, not re-dispersion. Excessive speed only entrains air, creates foam, and may generate heat that affects system stability. Low-speed thorough stirring with the blade submerged is the correct approach.
Q: Why does the color look right when wet but show color difference after drying?
A: In the wet film, water and dispersion medium have not yet evaporated. The refraction and scattering of light within the film differ from the dry state, so the visual color perception differs. The correct practice is to use the fully dried coating film for color comparison, in a standard light booth, at the same angle as the standard panel, and avoid making judgments based on the wet film.
Q: Can colorants from different brands be mixed?
A: In principle, it is not recommended. Different manufacturers’ dispersant systems, pH ranges, and additive compatibilities may differ. Mixing can easily lead to flocculation, sudden viscosity changes, or storage instability. If mixing is absolutely necessary, a compatibility small test must be done first, followed by at least one week of room-temperature storage observation plus elevated-temperature accelerated storage observation. Only after confirming no abnormalities can a small trial batch be used.
Waterborne Pigments、Waterborne Colorant、Waterborne Pigment Dispersion、Color Paste、Pigment Paste、Water-Based Color Paste、Colorant Paste、Paste Coloring、Colorant Processing、Pigment Preparation、Colorant Blending、Pigment Dispersion、Colorant Preparation、Colorant Mixing、Water-Based Pigment dispersion、Water-Based Color Paste、liquid Color Paste、liquid Color Paste、liquid Colorant