In the production of paints, plastics, or white masterbatch, TiO₂ is indispensable. However, many focus solely on whiteness and overlook a crucial factor coverage. Coverage determines how effectively TiO₂ hides the substrate color and influences its real-world efficiency. So how do we test it accurately? This article walks you through the entire process.
1. WHAT IS TIO₂ COVERAGE AND WHY IS IT IMPORTANT?
Coverage is the ability of a TiO₂ containing layer to hide the background surface. It’s expressed as the contrast ratio—based on light reflectance over black and white areas. Thanks to its high refractive index (~2.7), TiO₂ scatters light well, creating strong opacity. A high coverage TiO₂ achieves desired results even at lower loadings.
On the other hand, low coverage grades require higher doses, increasing cost and risk of defects. Accurate testing is not just quality control, it’s part of cost optimization and formulation strategy.
2. COMMON METHODS FOR TESTING TIO₂ COVERAGE
2.1. Black-and-White Chart Method (Contrast Ratio)
This method follows ASTM D2805 or ISO 6504-3 standards. A paint sample with TiO₂ is applied over a black–white contrast chart. After drying, the reflectance values (Y) over each background are measured. Contrast Ratio formula: (Y_black / Y_white) × 100%
A higher contrast ratio (closer to 100%) means better coverage. Exterior paints typically require ≥ 95% contrast ratio.
2.2. Consumption Rate Method (g/m²)
Prepare paint formulas with different TiO₂ grades and apply standard film thickness. Measure how much paint is needed to achieve target coverage. TiO₂ that delivers the same coverage at lower loading = better efficiency and lower cost.
3. FACTORS THAT AFFECT TIO₂ COVERAGE TEST RESULTS
3.1. Poor TiO₂ Dispersion
Undispersed TiO₂ forms agglomerates, reducing light scattering and coverage. The test won’t reflect the true potential of the material.
3.2. Inaccurate Film Thickness
Films that are too thick or thin distort reflectance readings. Dry film thickness should follow standards: typically 38–50 µm.
3.3. Resin System and Formulation Variables
TiO₂ performs differently across acrylic, alkyd, PU, or PVC systems. The same TiO₂ may yield different results depending on the formulation base.
4. BEST PRACTICES FOR ACCURATE TiO₂ COVERAGE TESTING
To compare TiO₂ grades fairly, use the same base formula and only change the TiO₂. Control key parameters such as mixing speed, dispersion time, and resin-to-filler ratio. Apply the coating using a standard drawdown bar on a black–white panel for even film thickness. After drying under controlled time and temperature, measure reflectance with calibrated devices. Repeat the test 2–3 times to minimize error and improve accuracy.
5. QUICK COVERAGE TESTING AT THE FACTORY FLOOR
Even without lab equipment, quick coverage tests can be done in production. Use a black-white panel and a 50 µm gap drawdown bar to ensure consistent film thickness. Weigh each paint sample accurately before applying for reliable comparison.
Once dry, observe color contrast with a white light source. If available, use portable reflectance meters (BYK, X-Rite) to measure Y values. Compare results to select the TiO₂ with the best coverage for your current formula.
6. CONCLUSION
Not all TiO₂ grades perform the same—even if they look equally white. Only through proper coverage testing can you identify which offers the best value and efficiency. Though it takes effort, testing helps reduce costs and improve product quality in the long run.
Looking for consistent, high-quality TiO₂ with professional support? Vichem provides technical advice, product recommendations, and testing guidance. From raw material to final product – we help you get coverage right.
📞 Phone: 0817 901 790
📧 Email: contact@vichem.vn
🔎 LinkedIn: Vichem JSC
🌐 Website: Vichem.vn
