Aluminum paste is widely used in coatings, inks, plastics, and industrial coatings. However, many manufacturers and users still face the problem of sedimentation and stratification, a common but easily misunderstood issue. As a leading manufacturer in Asia, Zhangqiu Metal Pigment Co., Ltd., based on materials science and nearly forty years of production experience, provides you with professional solutions.

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Understanding Aluminium Paste: Core Principles

Aluminium paste is a mixture of aluminium flakes + solvent + additives. Its stability depends on flake density, solvent viscosity, particle size distribution, surface treatment, and storage conditions.

Even high-quality aluminium paste can settle, but controlled settling without hard sediment is acceptable. The real problem occurs when settling becomes hard, compact, or forms a clear liquid layer, affecting performance.

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Typical Manifestations of Settling and Layering

1. Clear Liquid Layer on Top

You open the drum and see a bright solvent phase separated from the metallic portion.

2. Aluminium Flakes Accumulating at the Bottom

Soft sediment is normal; hard sediment indicates formulation or storage problems.

3. Viscosity Drop During Storage

Paste appears thinner because the heavy metallic phase has moved downward.

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Why Aluminium Paste Settles: Main Scientific Reasons

1. Density Difference (Physical Law)

Aluminium has a density of 2.7 g/cm³, much heavier than organic solvents (~0.85 g/cm³).
This natural density difference causes downward movement over time.

2. Particle Size Distribution Issues

• Large flakes settle faster

• Small flakes stay suspended longer

An uneven distribution or excessively coarse particles accelerate layering.

3. Insufficient Surface Treatment

Untreated or poorly treated aluminium flakes may:

• Lose compatibility with resin systems

• React weakly with dispersing agents

• Cause flocculation → faster settling

Resin-coated aluminium flakes have significantly improved stability.

4. Incompatible Resin or Solvent System

When aluminium paste enters a coating system, incompatibility causes:

• Flocculation

• Agglomeration

• Density-driven separation

This is common in low-polarity or acidic environments.

5. Storage Conditions

Authoritative laboratory data from ASTM D2196 stability tests show:
High temperature accelerates sedimentation by 2–3×.

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Key Factors Behind Settling: Expert Breakdown

Oil-Based vs Water-Based Systems

• Oil-based coatings: Most aluminium paste applications; more stable.

• Water-based coatings: Higher risk due to hydrogen reaction; must use water-based aluminium paste.

Leafing vs Non-Leafing Aluminium Paste

• Leafing: Flakes float closer to the surface → slower settling

• Non-leafing: Disperse throughout system → more sedimentation risk
  Most industrial coatings use non-leafing, so settling is unavoidable.

Coated vs Uncoated Aluminium Paste

• Uncoated (standard): More settling, weaker chemical stability

• Resin-coated or silica-coated: Better suspension, better oxidation resistance, lower hydrogen risk

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Applications & Comparative Insights

How Different Industries Manage Settling

Key Insight

According to industry reports from the Asia-Pacific Coatings Journal, demand for high-stability aluminium paste grew over 12% in 2024, mainly due to stricter quality standards.

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FAQ — Common Questions About Aluminium Paste Settling

Q1: Is settling normal?

Yes. Aluminium paste naturally settles because of density differences. Abnormal settling forms hard sediment.

Q2: How can I prevent severe layering?

Use resin-coated aluminium paste, increase viscosity, avoid high temperature, and ensure resin compatibility.

Q3: Can stirring restore stability?

Soft sediment can be stirred back easily; hard sediment indicates formulation issues.

Q4: Does settling affect brightness?

Yes. Agglomerated flakes cannot orient properly, reducing metallic effect.

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Conclusion — Get Professional Support from an Industry Leader

Stable aluminium paste comes from correct formulation + proper surface treatment + right application conditions.
If your current material shows settling, layering, or stability issues, our technical team can help analyze your system and provide optimized solutions.
Contact ZHANGQIU METALLIC PIGMENT
Website: https://zqmetallic.com/
Email: info@zqmetallic.com