Storage Stability in Paints and Coatings

How stability affects performance, longevity, and real-world reliability of coating systems.

Paints and coatings seem straightforward from the outside, a colorful product packed neatly in cans, ready to bring life and protection to surfaces. But behind that apparent simplicity lies a complex and constantly evolving world of chemistry, physics, material science, and environmental interactions.

From the moment a paint batch is produced to the final moment it is applied on a wall or structure, it undergoes several stages of transportation, handling, temperature exposure, and storage conditions.

This entire journey tests one invisible yet incredibly important property: Storage Stability in Paints and Coatings.

At Sakshi Chem Sciences, we understand stability not just from a laboratory perspective but from real operational experience.

With two decades of work in the chemical and construction industry, supplying globally across multiple climatic zones, we know that a paint formulation is only as good as its ability to remain stable and predictable through its shelf life.

A coating may have a beautiful finish, excellent adhesion, superior coverage, and perfect durability, but none of these qualities matter if it fails inside the container.

This long-form guide explores everything you need to know about storage stability: what it means, why it matters, how different factors affect it, how to identify instability early, and how formulators can enhance stability through proper formulation choices.

Whether you’re a manufacturer, technician, contractor, or coatings professional, this article gives you the clarity and depth needed to understand this crucial property.

What does Storage Stability Mean? 

The successful application of a coating or paint is dependent on the ability of the coating/paint to maintain the properties for that coating/paint maintained throughout the expected shelf-life of the product based on the manufacturer’s guidelines (or normal conditions) of use and storage, such as:

As a result of the details of the storage stability definition, some might identify a well-maintained/conditioned coating/paint because it behaves in accordance with expected characteristics when opened.

Some examples of coating/paint characteristics that would indicate storage stability are:

1. No physical or chemical deterioration occurs during normal use of the product

2. Coatings/paints retain their application characteristics after the re-opening of the container(s).

3. Coatings/paints remain chemically compatible with themselves after opening and being put back into use.

A Paint with Good Storage Stability Remains:

1. All components would remain uniform and well-mixed.

2. The viscosity would remain within standards.

3. There would be no lumps or foul odors or microbial contamination.

4. All colors would remain the same in color strength and opacity.

5. The paint would be ready to use after mixing with the appropriate solvent.

For that reason, storage stability cannot simply be looked at as a technical measurement of a given product but rather represents the quality of the overall production of a paint—formulation quality, manufacturing precision, compatibility of all raw materials, and reliability of the added additives.

The Impact of Storage Stability Upon Paints and Coatings

While storage stability may appear to be an afterthought concern, it truly affects overall product performance, customer service, overall cost to manufacture a product, and, ultimately, a manufacturer’s reputation regarding their brand.

1. The Influence on Product Usability

When a customer opens a coating or paint product that has separated, gelled, or has a foul smell, that product will be rendered unfit for use, thus creating waste.

2. Financial Costs Associated with Storage Stability

The rejections, returns, rework and loss of product batches can be very expensive.

3. Customer trust and long-term relationships

Distributors and contractors lose confidence in brands quickly when they experience inconsistencies.

4. Compliance/Regulatory Alignment

Many countries require stability testing to be done prior to importing/transporting a product into their market.

Real World Resistance:

Paints are shipped through diverse climates and must be able to withstand anything from the most severe heat, to freeze-thaw cycles, to extremely high humidity and shipping/transportation vibration.

At Sakshi Chem Sciences, stability is not a checkbox; it is the basis for all phases of R&D, raw material testing, and manufacturing.

Why Powder Coatings Have Different Stability Concerns Than Liquid Coatings?

It is helpful to understand what the paint system is to understand why paints have different levels of storage stability due to their formulation.

Powder Coatings

• Primarily Solid State Raw Materials.
• Very Stable at Standard Temperatures.
• Minimal Risk of Microbial Growth.
• Minimal Chemical Reactivity.
• Primarily Susceptible to Excessive Heat.

Powder Coatings are able to maintain stored stability significantly more effectively than Liquid Coatings.

Liquid Coatings

Liquid Paints Contain:

• Water or Solvent.
• Dispersed Pigments.
• Binders and Polymers.
• Various Types of Additives.
• Preservatives.
• Stabilizers.

These components are all interacting; temperature, microbial presence, chemical compatibility, and quality of the container all influence their long-term stability.

Most of the time, water-based and solvent-based liquid coatings will fail in storage due to gelling, sedimentation, and/or odor.

Key Factors That Affect Storage Stability

A description of how chemical interactions and scientific principles dictate the ability of paint to remain uniformly consistent throughout its shelf life.

1. Dispersion Stability – The Primary Ingredient in Coating Consistency

Fillers and pigments are considerably denser than their dispersive agent; should dispersion become unstable, those components will settle at the bottom or bond in a hardened state, rendering them unre-usable.

What Good Dispersion Provides?

• Uniform and smooth surface.
• Consistent viscosity throughout.
• Even colour shade.
• The right degree of hiding and opacity.
• Stability for extended periods of time.

Common Indicators of Dispersion Problems:

• Hard settlement in the base of the container.
• Clumps that won’t break apart easily.
• Inconsistent colour.
• Non-uniform application.
• Defects in the film.

How Dispersion Becomes A Problem?

The Dispersant was incorrectly selected:

• There was too little or too much dispersed agent used.
• Poor wetting occurred when connecting to any pigment.
• Re-agglomeration of particles.
• Exposure to Heat.

At Sakshi Chem Sciences we conduct research on pigment surface chemistry to select those dispersants that provide the most electrostatic and/or steric stability for maximum durability.

2. Rheology And Flow Characteristics When Stored

The Rheological properties of a given paint indicate how the material will operate while being stored as well as how it will flow, and resist settling during application.

Rheological breakdown leads to:

• Stringiness.
  
• Phase separation.
  
• Thick lumps.
  
• Inconsistent spread.

Why Rheology Changes Over Time?

• Temperature fluctuations.
  
• Polymer degradation.
  
• Water loss.
  
• Additive interaction.

To maintain a stable paint system, it is important to select the correct rheology modifiers. Selecting rheology modifiers will provide stability during all phases of paint production, from the lab to transportation and on the shelf.

3. Colloidal Stability: Maintaining Balance

Paints are colloidal shortenings that have a specific relationship with the liquid medium (solvent) in which they are suspended. The ability for pigment particles to remain suspended is determined by the balance between the pigment particle and the medium around it.

Reasons for Colloidal Unstability

1. Low repulsive forces.

2. Lack of compatibility between the stabilizer and the media.

3. Shifts in pH.

4. Imbalances in particle size distribution.

Consequences of Colloidal Unstability

1. Flocculation.

2. No shine.

3. Poor film formability.

4. Decreased gloss and opacity.

To provide good colloidal stability, the following need to be used in combination:

1. Electrostatic stabilizers

2. Steric stabilizers

3. Polymeric dispersants

These types of stabilizers keep the particles from coming into contact with each other and forming agglomerates.

4. Microbial Contamination: The Greatest Threat to Water-Based Paints

Water-based paints are the most favourable environment for microbial growth. If microorganisms infiltrate the paint, they consume the organics in the paint and produce harmful byproducts.

Indications of Microbial Contamination in Paint

1. Unpleasant odour of decayed or fermented substances.

2. Bubbles of gas or bloated laundry-type containers.

3. Very low viscosity.

4. Stringy texture.

5. Change in colour.

6. Sedimentation.

Causes of Microbial Contamination

1. Introduction of contaminated water.

2. Poor practice in the production area.

3. Poor containment of the end product.

4. Inadequate preservative systems.

Ways to Prevent Microbial Contamination

1. Use of broad-spectrum, in-can preservatives.

2. Enforcing strict hygiene procedures in the production plant.

3. Testing raw materials for microbial contamination.

4. Regular monitoring of the pH of paints.

Microbial contamination can destroy storage stability and must be controlled aggressively.

5. Temperature Instability: The Most Unpredictable Stability Factor

Temperature plays a major role in how stable a coating remains.

Effects of High Temperatures

• Accelerates solvent loss.
  
• Increases viscosity.
  
• Promotes skin formation.
  
• Speeds up chemical reactions.
  
• Causes bacterial growth.

Effects of Low Temperatures

• Causes freeze-thaw damage.
  
• Breaks emulsions permanently.
  
• Leads to coagulation.
  
• Promotes particle agglomeration.

Temperature is especially important during transportation. Many regions experience seasonal extremes that push coatings beyond their normal stability limits.

6. Chemical Reactions Inside the Paint Can

The chemical composition of paint continues to slowly undergo predictable chemical transformations, even when stored.

Examples of reactions that decrease stability include:

Oxidation

• Yellowing 
• Thickening
• Decreased binder integrity

Hydrolysis

Hydrolysis occurs when moisture interacts with reactive ingredients.

Acid-Base Reactions

Acid-base reactions can initiate changes in viscosity and, therefore, can destabilize the paint.

Photochemical Reactions

Ultraviolet (UV) light can cause pigment degradation and color fading.

Container Corrosion

Metal oxides can contaminate a product and change its chemical structure.

Reactions such as the ones listed above are why manufacturers need to use stabilizers, antioxidants, and corrosion-resistant containers.

7. Packaging Quality: The First Line of Defense

When a manufacturer uses a poor container, the following will likely occur:

• Leaking from container.
• Rust flakes in paint.
• Exposure to oxygen.
• Contaminated product.
• Evaporation of solvents.

A good quality container has the following characteristics:

• Keeps a tight seal on container.
• Does not corrode.
• Stays at a constant temperature.
• Protects from contamination.

Packaging may appear to be simple, but packaging is very important for keeping paint secure over an extended time period.

Signs That Paints Will Have Poor Storage Stability

Manufacturers and / or users can identify quality rapidly by looking for the following signs:

1. Phase separation 

The appearance of layers in paint suggests temperature-stress or incompatible ingredient issues.

2. Sedimentation 

If the pigments start to settle to the bottom of the container, soft sedimentation is reversible; however, hard sedimentation is not.

3. pH drift 

Tends to indicate that chemical reactions or microbial activity are happening.

4. Color change

Due to oxidation or UV degradation.

5. Viscosity indexing 

Paints can drastically increase or decrease in viscosity.

6. Gelling

Paint turns into jelly and becomes unusable.

7. Skinning

Surface drying due to solvent loss or oxygen exposure.

8. Gassing

Caused by microbial metabolism or chemical instability.

9. Odor Formation

Strong indication of microbial spoilage.

Every defect listed above reduces the coating’s ability to deliver its intended performance.

Standard Methods to Test Storage Stability in Paints and Coatings

Manufacturers use the following internationally recognized methods to properly measure stability:

• ASTM D1849 – Packaging Stability Test – evaluates: The odor of material, The effect of environmental factors (temperature) on the stability of coating materials, and whether the application of the coating materials causes skinning.

• ASTM D3925 – Practice for Sampling – provides an unbiased method of collecting a representative sample without introducing contamination into the sample.

• ASTM D869 – Evaluating Settling of Pigments – determines: How well pigments settle, The ease of remaking pigment mixtures, And whether or not the pigment will remain usable after being stored.

• ASTM D2243 – Freeze and Thaw Resistance – Tests the impact that cold climates and shipping will have on water-based (latex) coatings.

A manufacturer’s best way to maintain stability is by:

• Selecting the right cannot-dissolve materials.
• Selecting the appropriate ratio of materials for keeping consistency.
• Adding a stabilizer that maintains proper distances between pigment particles.
• Using anti-microbial preservatives in water-based systems to protect against mould growth during storage.
• Controlling the conditions used during manufacturing materials to ensure correct performance.
• Monitoring pH (or acidity) levels during the entire manufacturing process and through storage of finished materials.
• Using antioxidants and UV light blockers in the manufacturing process when necessary.
• Using only high-quality, strong containers (corrosion-resistant containers) that do not contribute to the decline of the product.
• Conducting performance tests of finished products prior to packaging.

At Sakshi Chem Sciences, we apply these concepts and techniques when developing our products to provide consistent and reliable performance globally.

Best Handling Practices for Users and Distributors

Once a paint product leaves the manufacturer, proper Handling Techniques should be in place to protect the storage stability of the paint.

✓ Store the paint at the ideal Temperature.

Avoid freezing (lower than 32F) and overheating (higher than 100F).

✓ Keep the Container closed off and sealed.

This will help to avoid any possible oxidation or microbial contamination.

✓ Protect the Paint from direct sunlight.

The UV rays will degrade the paint faster than time itself.

✓ Do not use contaminated tools.

Using contaminated tools will introduce bacteria into the paint or coating.

✓ Always stir the paints slowly before application.

This will redistribute all the pigments and ensure that they have a uniform texture.

By following these basic techniques, users of paint products will be able to maintain the quality of the paint and be concerned with the longevity of the paint.

Conclusion

The Quiet Guardian of Paint Quality is Storage Stability

Once the paint is made, Storage Stability is the deciding factor on whether or not a Coating can withstand the effects of shipping, storage, and fluctuations in Climate over time without compromising the integrity of the coating. 

The Paint Manufacturer (Not the end-user/customer) will determine whether or not The Paint performs based on conditions, not just the way it looks once applied.

At Sakshi Chem Sciences, Storage Stability is one of our 6 founding Principles. We have been designing and manufacturing paint for over 20 years and have the necessary R&D support, Equipment, and Quality Commitment to ensure that our coatings are as stable/reliable and Compatible as possible across every possible real-world environment.

The science is not simple, but our Company’s Philosophy is.

A paint that performs on Day 300 should be just as reliable as it was on Day 1.

Frequently Asked Questions (FAQs)About Storage Stability in Paints and Coatings