Titanium dioxide buyers have a new international testing reference. On October 16, 2026, the International Organization for Standardization published ISO 787-24:2026, covering photometric comparisons of pigment tinting strength and the relative scattering power of white pigments.
For manufacturers using titanium dioxide (TiO₂, CAS 13463-67-7) in paints, plastics and coatings, the new edition provides a timely reason to examine how suppliers report optical performance.
A pigment described as having 110% relative scattering power is not automatically 10% more effective in every coating formulation. The number depends on the reference pigment, testing method and controlled preparation conditions.
The main purchasing question is whether two pigments were tested using a genuinely comparable optical method—not which supplier reports the largest percentage.
The new standard also highlights an important technical distinction: scattering power, relative tinting strength, tint undertone and finished-coating hiding power are related properties, but they do not measure precisely the same thing.
What Changed With ISO 787-24:2026?
The new edition of ISO 787-24:2026, Photometric Methods for Pigment Testing replaces ISO 787-24:1985.
Its published scope covers two different applications.
The first concerns the relative tinting strength of similar coloured pigments.
The second concerns the relative scattering power of white pigments of the same type.
For both applications, the standard specifies comparison methods involving pigments dispersed in an alkyd resin without a drier.
This is important because the measurement is performed within a defined laboratory system rather than directly in every customer’s finished product.
The standard was published on October 16, 2026, after progressing through ISO’s international development and approval process.
It is now the current international edition.
However, the publicly available ISO description does not establish every procedural difference between the 1985 and 2026 editions.
Laboratories should review the complete published requirements before claiming that historical results are directly interchangeable with results obtained under the new edition.
The publication also does not automatically require every titanium dioxide supplier to replace its existing testing procedure.
The correct requirement depends on the applicable purchasing specification, contractual agreement and any relevant regulatory or industry obligations.
For buyers, the immediate value is clearer technical comparison and better document control.
Why Titanium Dioxide Scattering Power Matters
Titanium dioxide is widely used as a white pigment because its high refractive index enables it to scatter visible light effectively.
Light scattering contributes to whiteness and the ability of a coating to conceal the surface beneath it.
When light enters a pigment-containing coating, it interacts with pigment particles and the surrounding binder.
Some light is scattered, some may be absorbed, and the resulting optical behavior affects the coating’s appearance.
The performance depends on several characteristics, including pigment particle size, size distribution, crystal structure, surface treatment and the surrounding formulation.
Commercial titanium dioxide pigments may also be engineered for specific applications.
A grade intended for an architectural coating may have different formulation priorities from one developed for plastic masterbatch production.
This is why nominal TiO₂ content alone does not establish optical superiority.
A pigment with a lower assay because of engineered surface treatments may perform better in a particular application than a nominally purer material.
The site’s existing guide to titanium dioxide purchasing specifications explains how purity, crystal form, dispersibility and surface treatment contribute to grade selection.
The newly published ISO method provides a more specific tool for comparing one aspect of optical performance.
Scattering Power Is Not a Complete Hiding-Power Test
Relative scattering power describes a pigment’s light-scattering behavior compared with an appropriate reference under specified laboratory conditions.
Hiding power describes how effectively a coating conceals the substrate beneath it.
These properties are closely connected, but the finished coating also depends on pigment loading, film thickness, dispersion, binder characteristics and other formulation variables.
A pigment with favorable relative scattering power may not deliver an equivalent percentage improvement in finished-coating opacity.
The laboratory result is useful evidence for screening and comparison. It is not an independent guarantee of commercial coating performance.
Scattering Power and Tinting Strength Are Not the Same Measurement
The terminology surrounding white pigment testing can create confusion.
ISO 787-24:2026 distinguishes relative tinting strength for coloured pigments from relative scattering power for white pigments.
However, other established test methods also use the term tinting strength when assessing white pigments.
For example, ASTM D2745-00(2023) describes the determination of relative tinting strength of white pigments through reflectance measurements of black tints.
The method compares a test pigment with a reference pigment of the same type and grade.
ASTM describes this as a useful quality-control measurement.
It also cautions that results obtained using laboratory dispersion equipment do not necessarily reproduce the behavior of the same pigments under different industrial dispersion conditions.
This creates an important purchasing distinction.
A result described as white pigment tinting strength under ASTM D2745 should not automatically be treated as equivalent to relative scattering power obtained under ISO 787-24:2026.
The two methods may both provide valuable optical information, but their sample preparation, reference system and calculation requirements must be examined.
A supplier comparing its product against a different reference pigment may also report a different relative percentage without any change to the actual material.
What a Relative Percentage Really Means
Consider a hypothetical laboratory comparison in which a reference white pigment is assigned a relative scattering-power value of 100%.
A candidate pigment produces a value of 108% under the same validated comparison procedure.
The result indicates that the candidate performed 8% higher than that reference on the measurement scale used.
It does not establish that the pigment contains 8% more titanium dioxide.
It does not prove that the buyer can reduce pigment loading by 8%.
It also does not demonstrate an 8% improvement in outdoor durability, gloss or finished-paint coverage.
The percentage is relative to the particular reference and test conditions.
These values are illustrative rather than actual supplier test results.
For procurement teams, the useful evidence is a controlled comparison against an appropriate agreed reference material.
A stand-alone percentage without that context has limited value.
Why Tint Undertone Needs a Separate Test
Another commonly reported pigment property is tint undertone.
This describes whether a titanium dioxide pigment produces a relatively bluish or yellowish appearance when evaluated in a tinted system.
It is relevant because white pigments can change the appearance of coloured coating formulations.
Two titanium dioxide grades may have similar whiteness in their untreated or untinted state but behave differently after a small amount of coloured pigment is introduced.
The appropriate reference depends on the intended coating application.
ASTM D6131-17(2023) specifically addresses the relative tint undertone of titanium dioxide pigments.
Its purpose is to evaluate the blueness or yellowness of a test pigment compared with an agreed reference.
The standard also connects tint undertone with the pigment’s effective particle size.
However, it recognizes that variations in the dispersion medium and mechanical dispersion method can affect the measured result.
That means a supplier’s undertone claim cannot be evaluated fairly without knowing the comparison conditions.
A bluish undertone is not automatically better than a yellowish undertone.
The desired appearance depends on the target color, formulation and customer requirements.
An industrial coating manufacturer may prefer a different pigment undertone from a plastic masterbatch producer.
A purchasing specification should define which appearance characteristic matters and how it will be tested.
The Difference Between Scattering Power and Lightening Power
A further distinction involves lightening power, sometimes called reducing power.
This describes a white pigment’s ability to lighten an appropriately prepared coloured mixture compared with a reference white pigment.
The relevant international standard is ISO 787-17:2019, Comparison of Lightening Power of White Pigments.
The standard specifies a general comparison method using an agreed reference pigment of the same type.
ISO identifies two procedures, including one suited to evaluating an individual sample and another more suitable for assessing several samples.
This is related to the commercial value of a white pigment, but it remains a distinct test framework.
A manufacturer may therefore receive several optical measurements for the same titanium dioxide grade.
One reports relative scattering power.
Another reports lightening power.
A third provides tint undertone.
A fourth may describe finished-coating opacity.
These measurements should not be combined into one supplier ranking without identifying what each method actually measures.
The results can complement one another, particularly when the buyer needs both a reproducible incoming quality-control test and evidence of finished-formulation performance.
Why Dispersion Conditions Can Change the Optical Result
Titanium dioxide pigments may contain fine particles that form larger agglomerates during handling or processing.
A pigment’s effective optical behavior can change depending on how successfully those agglomerates are dispersed within the test medium.
This creates a potential difference between the intrinsic characteristics of the pigment and the result obtained from a prepared dispersion.
For example, two laboratories may use the same nominal pigment grade but different mixing equipment or dispersion conditions.
Their measured optical properties may differ because the pigment was incorporated into the test medium differently.
The existing article on Hegman grind gauge versus particle size explains why the fineness of a prepared dispersion should not be confused with the full particle-size distribution of the original material.
That distinction also matters for optical evaluation.
A supplier may report a promising scattering-power result under controlled laboratory conditions.
The customer’s actual production equipment may disperse the pigment differently.
For that reason, initial pigment tests should be supported by representative coating or plastics trials when application performance is critical.
Why the Reference Pigment Must Be Controlled
Relative measurements are only as useful as their reference.
If Supplier A uses one reference grade while Supplier B uses another, their reported values may not be directly comparable.
The same problem arises if the suppliers use different binders, pigment concentrations, dispersion procedures or instrumental settings.
Before ranking products, the purchasing and quality teams should establish whether the reference material and applicable procedure are sufficiently consistent.
Where a critical commercial decision depends on the result, controlled comparative testing using a common reference can provide stronger evidence than comparing independent technical data sheets.
How Buyers Should Respond to the New ISO Edition
The October 2026 publication gives manufacturers a useful opportunity to review how optical performance is specified.
That review should begin by identifying which optical properties are important to the finished product.
For some coatings, hiding power is the main purchasing concern.
For others, undertone, shade consistency or behavior in a tinted formulation may be more important.
A company developing highly loaded plastic masterbatches may place different weight on dispersion behavior and processing performance.
The next step is to identify the testing procedures already used by suppliers and internal laboratories.
If a specification references ISO 787-24:1985, the buyer should examine the 2026 edition before changing its acceptance criteria.
Historical results should remain traceable to their original testing basis.
The buyer should not simply replace an edition number in the purchasing document and assume the measurements remain equivalent.
Similarly, a supplier’s previous declaration of compliance does not automatically establish compliance with an edition that was published later.
Appropriate laboratory personnel should review the revised standard and determine whether method validation, correlation testing or other document-control actions are necessary.
What Should Appear in the Supplier Qualification File
When relative optical measurements are part of the purchasing specification, the documentation should identify the tested pigment grade, method and edition, reference pigment, preparation conditions, reporting basis and agreed acceptance criteria.
The supplier should distinguish typical technical data from guaranteed specification limits.
A certificate of analysis should report the relevant result for an identified production lot when that property forms part of routine lot acceptance.
A technical data sheet may describe expected optical characteristics, but a typical value does not necessarily represent an agreed minimum performance requirement.
A safety data sheet communicates chemical hazards and appropriate handling information. It is not a certificate of scattering power, tinting strength or finished-coating opacity.
Independent laboratory testing can provide additional evidence, provided the tested samples and methods are suitable for the comparison.
Where measurements differ, the buyer should investigate the test basis before concluding that the pigment itself has changed.
A Better Optical Comparison Leads to Better Product Selection
The publication of ISO 787-24:2026 is a meaningful technical development for manufacturers evaluating white pigments.
It provides a current international reference for photometric comparison of relative scattering power within the standard’s defined conditions.
It does not eliminate the need for other optical measurements or finished-product testing.
For titanium dioxide buyers, the most useful approach is to distinguish scattering power from undertone, lightening power and hiding power.
Each property answers a different question.
A higher relative percentage is valuable only when the reference material, testing conditions and application requirements are understood.
The purchasing advantage comes from using these measurements together—not from treating the largest number on a supplier’s technical data sheet as proof of the best pigment.