Two coating formulations can contain the same weight of titanium dioxide yet deliver different opacity, gloss, water resistance and durability. One reason is that coating performance depends on the volume occupied by pigments and binders, not simply their weight.
This relationship is described by pigment volume concentration (PVC), a fundamental measurement in paint and coatings formulation.
For manufacturers purchasing titanium dioxide (TiO₂, CAS 13463-67-7), understanding PVC can help explain why changing pigment grades, replacing extenders or reducing binder content may alter finished-coating performance.
A second concept, critical pigment volume concentration (CPVC), identifies a transition where the binder is no longer sufficient to fill the spaces between pigment particles.
Crossing that threshold can change coating porosity, appearance and mechanical properties.
For industrial buyers, the important question is not whether a pigment has the lowest price per kilogram. It is whether the proposed pigment package delivers the required coating performance at a suitable pigment-to-binder volume ratio.
What Pigment Volume Concentration Actually Measures
Pigment volume concentration describes the proportion of a dry coating’s conventional pigment-and-binder volume occupied by pigments and extenders.
It includes primary pigments such as titanium dioxide and extender materials such as calcium carbonate, when present.
The basic calculation is:
PVC (%) = Pigment and extender volume ÷ (Pigment and extender volume + nonvolatile binder volume) × 100
Water and volatile solvents are excluded from this calculation because they are not intended to remain as part of the dry coating’s pigment-and-binder structure.
The UL Prospector technical explanation of pigment volume concentration emphasizes that ingredient weights must be converted into volumes using the relevant material densities.
It also notes that the nonvolatile portion of the binder must be distinguished from the liquid binder product as supplied.
This matters because an acrylic emulsion may contain substantial water.
Using the entire liquid emulsion volume as the dry binder volume would distort the calculated PVC.
The same issue can arise with solvent-based resins.
Buyers comparing formulations should therefore verify whether a supplier’s reported PVC reflects actual nonvolatile binder content rather than an assumed liquid-resin volume.
Why Equal Pigment Weights Can Produce Different PVC Values
Titanium dioxide has a relatively high density compared with many commonly used mineral extenders.
That means a kilogram of titanium dioxide can occupy less volume than a kilogram of a lower-density filler.
Consider two simplified hypothetical coating systems.
Both contain 40 kilograms of solid particulate material and 40 litres of nonvolatile binder.
In the first example, assume the particulate material is titanium dioxide with a density of 4.0 kg/L.
Its volume is:
40 kg ÷ 4.0 kg/L = 10 L
The pigment volume concentration becomes:
10 ÷ (10 + 40) × 100 = 20.0% PVC
In the second example, assume the particulate material is a mineral extender with a density of 2.7 kg/L.
Its volume is:
40 kg ÷ 2.7 kg/L = approximately 14.81 L
The resulting PVC is:
14.81 ÷ (14.81 + 40) × 100 = 27.0% PVC
Both hypothetical formulations contain the same mass of particulate material and the same volume of dry binder.
Yet their calculated pigment volume concentrations differ by approximately seven percentage points.
These calculations illustrate the relationship between density and volume. The density values are assumptions for this example, not measured specifications for particular commercial grades.
They are also not suggested production formulations.
Crucially, the second formulation would not necessarily provide better hiding power.
Titanium dioxide and mineral extenders have different optical properties. Replacing one with the other changes more than PVC.
The calculation demonstrates why weight-based comparisons alone cannot predict coating performance.
What Happens at Critical Pigment Volume Concentration?
Critical pigment volume concentration is the point at which the binder is just sufficient to fill the spaces between pigment particles and form the required binder structure.
Below CPVC, the binder can occupy the spaces between properly dispersed particles and form a comparatively continuous film.
Near CPVC, the formulation becomes more sensitive to pigment packing, binder properties and dispersion.
Above CPVC, insufficient binder is available to fill all the spaces within the pigment network.
Air-filled voids may remain after the coating dries.
These voids can significantly affect the film’s properties.
The Museum of Fine Arts Boston’s CAMEO materials reference explains that coatings above and below CPVC can show sharply different characteristics.
A high-PVC coating may become more matte and opaque but show reduced washability or increased chalkiness.
A lower-PVC coating may offer greater gloss and improved resistance to cleaning, depending on the complete formulation.
Neither outcome is automatically better for every application.
A decorative interior ceiling paint may prioritize a flat appearance and good hiding.
An industrial protective coating may place much greater importance on water resistance, adhesion and maintaining a continuous protective film.
The correct PVC must therefore be selected according to the finished product’s requirements.
Why CPVC Is Not One Fixed Percentage for Every Pigment
There is no universal CPVC value that applies to all titanium dioxide formulations.
The threshold depends on the complete pigment-and-binder system.
Important factors include particle size, particle-size distribution, particle shape, packing behavior, surface treatment and the binder’s ability to wet the particles.
Extender selection can also change the result.
For example, adding a mineral filler may influence how particles pack around titanium dioxide.
A suitable combination may improve packing efficiency, while a different combination may increase void space or binder demand.
These outcomes depend on the actual materials.
A coating manufacturer should not assume that replacing one extender with another preserves the original CPVC simply because the replacement has the same weight.
Likewise, switching between titanium dioxide grades can affect formulation behavior even when their nominal TiO₂ content is similar.
The Paint & Coatings Industry technical discussion of pigment calculations explains why resin wetting characteristics, surface area, particle dimensions and oil absorption complicate CPVC determination.
The article emphasizes that the critical transition must ultimately be established for the relevant formulation rather than assumed from a universal theoretical number.
For purchasing teams, this creates a useful qualification requirement.
A supplier’s stated pigment characteristics can help identify a candidate material, but the finished coating must still demonstrate acceptable performance under representative conditions.
Oil Absorption Provides a Clue, Not a Guaranteed CPVC
Oil absorption is often discussed alongside critical pigment volume concentration.
A pigment’s oil absorption result measures the amount of oil needed to bring the material to a defined consistency under a particular laboratory procedure.
Because the test relates to liquid demand and particle packing, it may provide useful information when estimating pigment binder requirements.
However, an oil absorption result is not automatically equivalent to CPVC.
The reference oil may interact with the pigment differently from the acrylic, alkyd, epoxy or other commercial binder used in the finished formulation.
Particle packing, formulation additives and dispersing conditions also influence the result.
The site’s guide to titanium dioxide oil absorption test methods explains why supplier oil absorption figures can differ when testing procedures and reference liquids are not equivalent.
That problem becomes especially important when a buyer attempts to estimate formulation changes using independently reported technical data.
A numerical difference in oil absorption does not automatically establish the same percentage difference in required binder.
Where CPVC is commercially important, the estimate should be checked through suitable laboratory evaluation.
Why Going Above CPVC Can Change Coating Durability
A formulation above CPVC may contain air-filled voids that influence the movement of water and other substances through the dry coating.
This can increase permeability and affect resistance to moisture.
For certain applications, that is a major consideration.
An exterior architectural coating may need to balance water resistance with other desired performance characteristics.
A protective coating on metal may require a continuous film that limits moisture and corrosive-substance access to the substrate.
The appropriate formulation depends on the protective mechanism and service environment.
In its ASTM D2697-22 standard on volume nonvolatile matter in coatings, ASTM discusses how pigment packing and binder-filled spaces affect the volume of a dry coating.
It notes that above CPVC, unfilled voids can make the apparent dry-film volume significantly greater than the theoretical value.
This means the predicted volume of a coating calculated from its ingredient quantities may not fully describe the resulting dry-film structure.
ASTM D2697-22 concerns a specific volume-nonvolatile measurement method. It is not a universal test for CPVC or an automatic qualification procedure for every coating type.
Nevertheless, the published discussion illustrates why unfilled voids matter when interpreting dry-film properties.
For procurement teams, this has an important consequence.
A formulation that appears economical because it contains less binder may create additional performance risks.
The initial material saving should be evaluated alongside resistance to wear, moisture, cleaning and the expected service environment.
Higher PVC Can Also Change Appearance
The relationship between PVC and optical performance is not entirely negative.
In some coatings, air-filled voids can contribute to light scattering, producing a form of dry hiding.
This can help explain why certain flat decorative coatings achieve good opacity at comparatively high PVC values.
However, the resulting film may differ from a lower-PVC coating in gloss, scrub resistance and durability.
A more opaque appearance is therefore not proof of better overall performance.
For industrial coatings, optical characteristics should be assessed alongside the protection and mechanical properties required by the application.
PVC Is Not the Same as Volume Solids
Another common reporting mistake is confusing pigment volume concentration with volume solids.
Both measurements use volume, but they describe different characteristics.
PVC concerns the relative volumes of pigment particles and nonvolatile binder in the conventional dry coating formulation.
Volume solids describes the volume of nonvolatile coating material remaining relative to the applied liquid coating volume, under a specified measurement basis.
A high-solids coating does not necessarily have a high PVC.
For example, a coating may contain relatively little volatile solvent while remaining rich in resin and relatively low in pigment.
Another coating may have a high pigment loading but contain substantial water before drying.
The two properties can therefore vary independently.
Purchasing teams should establish which measurement a supplier is reporting before comparing figures.
This is particularly important when a technical data sheet provides both volume solids and PVC without explaining the calculation basis.
The information may help estimate coating coverage and formulation characteristics, but neither value independently guarantees finished-film performance.
How Manufacturers Should Compare Alternative Titanium Dioxide Grades
A meaningful comparison should begin with the approved coating formulation.
If the existing product meets its performance requirements, that formulation provides a useful reference for evaluating an alternative pigment.
The buyer should confirm the identity and grade of the candidate titanium dioxide, along with relevant physical and optical characteristics.
The supplier’s technical information may include density, particle characteristics, surface treatment, oil absorption and other properties.
These measurements help identify possible differences.
They do not independently establish whether the new pigment will behave identically in production.
A controlled formulation comparison should establish whether changes to pigment volume, extender loading or binder requirements affect the finished coating.
Where necessary, qualified laboratory personnel can evaluate opacity, gloss, dispersion, viscosity, mechanical properties and other relevant performance criteria.
The purpose is not simply to match the original PVC.
A formulation can have the same calculated PVC while using different pigments or binders and still produce different results.
For exterior or protective coatings, service-related testing may be especially important.
The site’s article on titanium dioxide UV weathering and coating durability explains why accelerated testing must be interpreted alongside the actual coating system and its intended environment.
A favorable laboratory result should be connected to defined acceptance requirements rather than converted into an unsupported service-life promise.
What Buyers Should Put in Their Qualification Documents
A purchasing specification can identify titanium dioxide grade characteristics, relevant test methods and agreed material limits.
Where pigment density or another physical property affects formulation calculations, the reporting basis should be clear.
The supplier’s certificate of analysis can provide selected lot-specific measurements.
However, a CoA confirming pigment purity or another characteristic does not prove that the material will deliver acceptable PVC-related coating performance.
A safety data sheet communicates hazard and safe-use information. It does not certify critical pigment volume concentration or finished-film properties.
An independent laboratory report can provide additional evidence for the samples and tests performed, but its results need to be evaluated against the intended application.
For an important pigment substitution, the approval record should distinguish the supplier’s material properties from the manufacturer’s finished-product qualification results.
That makes later investigations more reliable.
If a coating changes appearance or performance after a supplier substitution, quality teams can examine the pigment, formulation calculations and production conditions separately.
Without those records, it may be difficult to determine whether the problem came from pigment characteristics, dispersion, binder content or another change.
The Best Pigment Value Depends on the Whole Coating
Pigment volume concentration connects raw-material selection with the structure of the finished coating.
It explains why equal pigment weights do not always produce equal results and why reducing binder content can affect more than the purchasing cost.
Critical pigment volume concentration adds another dimension by identifying where the pigment-and-binder structure begins to change significantly.
For titanium dioxide buyers, neither PVC nor CPVC should be treated as an isolated supplier ranking.
A pigment with a favorable price, density or oil absorption value may still need different formulation conditions to meet the customer’s requirements.
The strongest purchasing decision compares the total formulation, the relevant performance tests and the cost of achieving the required result.
The goal is not the highest pigment concentration or the lowest binder cost. It is a coating that delivers the intended performance consistently and economically.