Shimmer is not a colour. An effect pigment works by reflecting and interfering with light rather than by absorbing it, which means the same chemical substance can appear silver, gold, red or green depending on how thick a coating is on its surface. The property that makes effect pigments attractive is also the property that makes them difficult to specify, because a colour that depends on structure rather than on chemistry cannot be checked by a certificate of analysis alone.
This article covers the three parts of an effect pigment that a brand actually chooses: the substrate, the coating and the particle size. It then sets out the regulatory position a brand has to confirm for each market and the sourcing question that has moved from a niche concern to a standard item on a supplier questionnaire.
Why effect pigments behave differently from absorption pigments
A conventional pigment absorbs some wavelengths and reflects others, and the colour it produces is fixed by its chemistry. An effect pigment does almost the opposite. It reflects the light that reaches it, and it produces colour by interference between the part of the light reflected from the top of a coating and the part reflected from the bottom.
That structure is what makes the appearance dependent on the angle of view and on the light source. A bronze pigment in a pressed powder can look warm and matte in a compact under an office light and take on a metallic green cast on a cheek in daylight, and both readings are correct. It also explains why a shade standard agreed on a swatch table can look wrong on a printed carton, and why an effect pigment is usually specified with an instrument that measures at several angles rather than one.
The practical consequence for a brand is that an effect pigment specification cannot be reduced to a colour index number. Two suppliers offering the same index can deliver a noticeably different effect, because the index describes the chemistry and not the layer structure on top of it.
The substrate decides the effect
Every effect pigment is a thin platelet with something coated on it, and the platelet is the part the brand usually glosses over.
Natural mica is the traditional substrate. It is a mined mineral that splits into thin sheets, which makes it well suited to being coated, and it is inexpensive and widely available. Its limitations are variability between deposits, a supply chain that has attracted sustained scrutiny, and a degree of light absorption that reduces the brightness of the effect.
Synthetic mica is made rather than mined, which gives a more consistent platelet and a more controlled particle size distribution. It is brighter than natural mica for the same coating, it broadens the range of colours that can be built by interference, and it removes the mining question from the supply chain. It costs more, which is the reason it has not replaced natural mica everywhere.
Glass flake is a third substrate, made from a borosilicate sheet, and it produces the highest sparkle of the three because its surface is smoother and more uniform. It is the substrate behind the small, sharp glints that a highlighter relies on, and it is also the most expensive. Aluminium flake sits alongside these as a distinctly different look: it is opaque and mirror-like rather than translucent, and it produces a metallic effect with an entirely different relationship to light.
The choice among them is usually a decision about the promise on the pack. A soft, lit-from-within finish and a sharp sparkle are different products, and the substrate is what separates them.
Coating thickness and the colour that comes out of it
The colour of an interference pigment is set by the thickness of the coating, and by nothing else in the formula.
A titanium dioxide layer on a mica platelet reflects light from two surfaces, and the two reflections reinforce each other at a wavelength that depends on the layer thickness. A thin layer produces a silvery white, a slightly thicker layer produces gold, and progressively thicker layers produce red, blue and green. The same substrate and the same coating material therefore yield a family of colours, which is one reason a supplier's catalogue is organised by interference colour rather than by chemistry.
Iron oxide coatings behave in a related way with a different result, producing the bronze, copper and russet effects that a warm palette depends on. A combination coating, with iron oxide over titanium dioxide, produces the strongly saturated effects used in fashion-led ranges.
Multi-layer pigments, with several alternating layers, produce the most pronounced colour travel, where the shade shifts markedly between two viewing angles. They are the most expensive group and the most sensitive to any change in the coating process, so a shade matched on one production run may need to be re-matched for the next.
Particle size, and matching the pigment to the format
Particle size controls the visual texture of the effect, and the specification window differs by product type because the format decides how the platelet sits on the skin.
A fine fraction in the region of five to twenty-five microns produces a soft shimmer that reads as a sheen rather than as a sparkle, which is what a pressed eyeshadow or a foundation wants. A coarser fraction from ten to sixty microns produces the visible glints a loose highlighter or a baking powder depends on, and it is also the fraction most likely to be felt as grit on the face. A liquid lip product needs a fine fraction because a large platelet will not sit smoothly in a thin film and will be felt on the lip. A cream blush tolerates a broader range because the film is thicker.
The size distribution matters as much as the average, which is why a specification written as a single figure is not sufficient. A supplier quoting a median of twelve microns may be delivering a narrow distribution or a range from four to forty, and the second will look and feel different even though the median matches. Asking for the distribution and for a retained sample from the production lot is the way to make the specification meaningful.
Where the effect is central to the product promise, it is worth writing two limits into the specification: the median for the appearance and the top cut for the skin feel. Both are available from any pigment supplier who coats the substrate in-house.
Surface treatment and compatibility with the base
A pigment platelet has a surface, and the surface determines whether it disperses in the base or floats in it.
An untreated platelet is hydrophilic, which works well in a water-based gel and poorly in an anhydrous system, where it will agglomerate and reduce the effect. A silicone treatment makes the surface compatible with an anhydrous or silicone-heavy base and reduces oil absorption, which keeps a lip product from drying out over hours of wear. An amino acid or a surfactant treatment suits water-based formats and gives a lighter feel. A silane treatment improves adhesion and can reduce the photocatalytic activity of a titanium dioxide coating, which matters for light stability.
The mismatch to avoid is a pigment finished for one system used in another. A silicone-finished platelet in a water-based gel behaves as though the finishing were absent, and the formulator tends to blame the pigment rather than the pairing. Specifying the treatment alongside the base rather than separately removes the problem at the brief stage.
The regulatory position a brand has to confirm
Effect pigments are colourants for regulatory purposes, and the position differs enough between markets that a single pack rarely serves all of them without a decision.
In the European Union, mica is a permitted colourant under Annex IV of the Cosmetics Regulation, and it is also listed with anticaking, bulking and opacifying functions in the ingredient inventory. As with any colourant, its use is subject to purity criteria on heavy metals, so a brand should hold a specification for lead, arsenic and mercury rather than a general statement of compliance. In the United States, mica is listed as an exempt colour additive for drugs and cosmetics, with a restriction on which batch-certified dyes may be used to coat it. In China, colourants must be on the permitted list and the product dossier is filed before market entry, which makes the pigment documentation an input to a filing rather than a purchase record.
Titanium dioxide deserves separate attention because it is both the most common coating and a powder that can be inhaled. In the European Union, titanium dioxide in pigmentary powder form is restricted in cosmetics, with a higher limit for loose face powder and a much lower one for hair aerosol sprays, and with a general condition that it is not used in applications that may lead to inhalation exposure to the lungs. The classification that prompted the restriction was annulled by the General Court in November 2022, while the entries in the cosmetics annexes remained in place, so the position is one a brand should verify for its own market and product form rather than take from a supplier summary.
There is a second, unrelated trend that has moved the choices in this category: the European restriction on intentionally added microplastics, adopted in 2023, phases out conventional plastic glitter over a transitional period. Brands that built a visual identity on plastic glitter have been reformulating toward mineral and glass-based effects, which increases demand for the substrates described above.
Sourcing, traceability and what a supplier questionnaire should ask
The mica supply chain has become a standard item in brand due diligence, and the questions a buyer asks have become more specific over the past few years.
Mica is mined in a number of regions, and informal mining in some of them has been associated with child labour and unsafe working conditions. Industry initiatives exist that audit and trace the supply chain, and a supplier claim under one of them should be backed by documentation that identifies the mine or the processor rather than a statement of principle. The most defensible position for a brand is a supplier that either operates under a recognised traceability framework with third-party verification, or supplies a synthetic substrate whose origin is a factory rather than a mine.
Traceability also has a practical dimension for a formulator. A pigment whose substrate varies between deposits will vary in effect, so a brand that has approved a shade on one lot and does not control the substrate source will see the shade move without any change to the formula. Specifying the substrate source, and not only the interference colour, is what makes an effect standard reproducible.
Effect pigment variables at a glance
| Variable | Typical position | What it controls | Failure sign if wrong |
|---|---|---|---|
| Substrate | Natural mica, synthetic mica, glass flake or aluminium | Brightness, sparkle character and sourcing story | A finish that reads as dull against the approved standard |
| Coating thickness | Set by interference colour rather than by weight | The colour of the effect itself | Shade drift between production lots |
| Particle size window | 5 to 25 microns for pressed formats, 10 to 60 for loose | Sheen against sparkle, and skin feel | Gritty feel, or an effect that disappears on application |
| Size distribution | Median plus a top cut, both specified | Consistency between lots | Two batches that match on paper and not on skin |
| Surface treatment | Matched to the base, silicone for anhydrous, amino acid for aqueous | Dispersion and oil absorption | Agglomeration and a weaker effect than designed |
| Titanium dioxide coating | Checked for photocatalytic activity where light stability matters | Colour retention in the pack | Shade change under retail or daylight exposure |
| Purity documentation | Heavy metal specification per colourant rules | Market acceptance | A dossier that cannot be filed |
| Sourcing evidence | Traceability framework or a synthetic substrate | Due diligence and brand risk | A supplier claim with no documentation behind it |
Stability and the loss of effect
An effect pigment can remain chemically unchanged and still lose its appearance, because the appearance depends on structure that can be broken.
The first loss mechanism is platelet damage. A glass flake or a mica platelet that is broken in a mill, in a high-shear mixer or in a pump loses its interference behaviour, and the result is a duller, flatter finish. This is why effect pigments are added late in the process, after the pigment dispersion has been milled, and why the mixing step is specified as gentle and short.
The second is agglomeration. Platelets that are not properly wetted clump, and a clump behaves optically as a larger particle, which shifts the effect toward a coarse sparkle. The remedy is in the wetting step and in the surface treatment rather than in the mixing speed.
The third is migration in storage. An anhydrous stick or a cream can let the platelet settle or concentrate at a surface over time, which shows up as a product that looks different in the middle of the pan from the edge. A stability study for a format with a high effect load should include a close look at the surface distribution rather than only at the bulk colour, because the difference will be noticed by the customer on the first use.
A stability check for a format containing more than a few per cent effect pigment should also measure colour at more than one angle. A single-angle measurement can show a match between two samples that differ visibly in colour travel, which is exactly the complaint a customer makes.
What to put in the brief
An effect specification is only reproducible when the substrate, the coating, the size window and the sourcing route are all named, and the brief is the place they get named.
Describe the finish in observable terms, since a phrase like luminous or multi-dimensional means different things to different people. State the format, because the format sets the size window. State the base chemistry, because it sets the treatment. And state which markets the product will be sold in, because the pigment documentation has to satisfy all of them.
- The finish in observable terms, sheen, sparkle, metallic or colour travel.
- The format and the film thickness it produces, which sets the size window.
- The base chemistry, aqueous, anhydrous or silicone-heavy.
- The substrate preference, including whether a synthetic route is acceptable.
- The interference colour family, if the effect is central to the shade.
- The particle size window with both a median and a top cut.
- The markets of sale, so the colourant documentation follows from the start.
- The traceability evidence the brand will need for its own due diligence.
Answering those lines before a shade is approved avoids the two outcomes that cost the most: a standard that cannot be reproduced because the substrate was never fixed, and a documentation set that cannot meet a market's filing requirement.
Where our capability fits
We develop colour cosmetics with effect pigments specified by substrate, coating, size window and treatment rather than by colour index alone, so a shade standard holds between production lots and the finish that was approved is the finish that ships. Colour is measured at more than one angle, and pigment entries are documented against the colourant rules of the markets each product is destined for.
We work with brands on private label (your brand on a proven base), OEM/ODM contract manufacturing, and full custom formula development — whichever matches where your brand is today. Our lines include a long-lasting waterproof foundation, a colourful fragrance range and a vitamin C brightening face cream, all of which rest on the same pigment documentation and dispersion disciplines that an effect programme needs.
Tell us the finish you are aiming for, the base and the markets, and we will map the substrate choice, the size window, the treatment and the documentation set against your shade standards. Start at our inquiry page, email capsulebiotech@163.com, or message the right team on WhatsApp: Capsule Series (capsules only) +86 158-7655-5319, Cosmetics Series (serum, hair care, body care, fragrance) +86 158-7655-5319. Pigment architecture is covered in our article on shade ranges and pigments, and ingredient documentation in our guide to INCI names and ingredient rules.
General manufacturing information, not regulatory or legal advice. Permitted colourants, purity limits, concentration limits and labelling requirements vary by market and by product, and the applicable rules should be confirmed for each market before a formula is finalised.