Introduction: For small and medium-sized paint factories, paint sedimentation and caking during production are far from minor issues. They directly lead to product scrap, increased rework costs, and delivery delays, acting as a clear indicator of shortcomings in production processes and quality management. Management must understand that these are not random occurrences solvable by a simple “shake.” They often reveal hidden risks across the entire chain, from formulation and raw materials to production and storage. This article provides an in-depth analysis of the causes and offers systematic solutions, from immediate countermeasures to root cause prevention.
What Are Sedimentation and Caking in Paints?
- Sedimentation: During storage, the solid components of the paint sink to the bottom of the container, resulting in a thin-on-top, thick-at-bottom phenomenon with sediment at the bottom.
- Caking: When sedimentation is severe, the material at the bottom forms dense lumps that cannot be re-dispersed by stirring.
- High-Risk Products: Products using high-density pigments like red lead paint, anti-rust paints (e.g., micaceous iron oxide), and anti-fouling paints are high-risk areas for this problem.
Common Causes of Paint Sedimentation and Caking
- Formulation Design Issues:
- Excessively high Pigment/Binder Ratio (P/B Ratio), high usage of fillers.
- Use of pigments with high specific gravity (e.g., red lead powder, chrome yellow, micaceous iron oxide, precipitated barium sulfate).
- Failure to add or insufficient use of anti-settling agents.
- Production Process Issues:
- Excessive addition of thinner, resulting in low paint viscosity.
- Poor grinding and dispersion, leading to coarse pigment particles.
- Raw Material and Storage Issues:
- Reaction or adsorption between pigments and paint resin, causing gelling.
- Storage temperature too high (exceeding 25°C) or storage time too long, exceeding the shelf life.
Solutions to Prevent and Fix Paint Sedimentation/Caking
- Formulation Optimization:
- Control the Pigment/Binder Ratio (P/B Ratio), generally not exceeding 2:1. Consider using lower-density pigments where appropriate.
- Add anti-settling agents such as stearate series, fumed silica, organoclay, hydrogenated castor oil to create thixotropic paints.
- Avoid using reactive pigments and fillers; consider separate packaging for zinc powder, aluminum powder, etc.
- Production Process Control:
- Ensure thorough grinding and dispersion to achieve specified viscosity and fineness.
- Strictly control the amount of thinner added to prevent excessively low viscosity.
- Storage and Management Measures:
- Store paint in a cool, ventilated place at 15-25°C.
- Regularly lay horizontally, invert, or shake the paint drums.
- Follow the FIFO (First-In, First-Out) principle and pay attention to the product shelf life.
- Problem Product Handling:
- Sedimented material can be used after uniform stirring.
- For caked material, pour out the liquid first, crush the sediment, and then remix. If it cannot be dispersed, it must be scrapped.
What We Can Offer
If your paint or ink factory faces sedimentation or caking issues, we provide:
- Custom formulation design – improve pigment dispersion and stability.
- Raw material supply – dispersants, wetting agents, and anti-settling additives.
- Technical guidance – from lab scale to full production.