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Réponse rapide: I would not test primer and foundation as two isolated formulas. I would test one primer on a defined foundation matrix, standardized sub-layers of skincare and sunscreen, fixed dry-down intervals, controlled application methods and time-course wear conditions. The protocol should document pilling, sliding, levage, irrégularité, uniformity of coverage, tack, pore settling, creasing and shine at pre-defined checkpoints.
For regulatory context, I do not treat this as an FDA- or ISO-mandated primer/foundation test method. FDA states that it does not maintain a fixed list of tests required for every cosmetic product or ingredient; manufacturers remain responsible for determining appropriate testing and supporting product safety. FDA Product Testing of Cosmetics
Why Testing Primer Only on Bare Skin Creates a Development Blind Spot
There is still a place for bare-skin evaluation. It tells me how it slips, how it tacks up, how it dries down, how it blurs, how it feels after application and whether the primer itself pills when rubbed. I would leave it as a control condition.
But I would not make it the primary condition for approval.
A customer can use serum, moisturizer and sunscreen before primer. The next level can be silicones, volatile carriers, pigments, poudres, film-forming polymers and a completely different emulsion architecture. By the time foundation hits the skin it is no longer “skin”; it is a multi-layer cosmetic surface.
This way of thinking is supported by research published on cosmetic pilling. UN 2024 study on skincare, sunscreen and foundation layering in 528 femmes, published in Skin Research and Technology, found that pilling was affected by stage of product application, application method and skin properties, rather than indicating one universal ingredient mismatch. 2024 Study: Understanding the Causes of Skincare Product Pilling
That changes the question of development for me. Rather than asking, “Does this primer feel good?” I ask:
“Will this primer give a stable, repeatable surface for the make-up systems that our customer is likely to actually use?»
That question must be answered by the compatibility protocol.
For brands that are still defining the wider primer concept before reaching this testing stage, I would treat compatibility as one part of the complete development process rather than a final check added at the end.
Comment développer une base de maquillage de marque privée | FERMÉ
Start With a Primer–Foundation Testing Matrix
je le ferais’t take ten random foundations off the market and start applying them to the sample. That leads to a lot of observations, but not necessarily useful formulation information.
D'abord, I categorize the foundation systems that I want the primer to cover.
That is how a practical B2B testing matrix could look:
| Foundation Test Class | What I Am Trying to Challenge | Main Compatibility Risks I Watch |
|---|---|---|
| Water-in-silicone / silicone-continuous liquid foundation | Silicone-rich continuous phase, glisser, volatile dry-down | Sliding, coverage thinning, levage, excessive lubricity |
| Anhydrous or silicone-rich foundation | High compatibility with lipophilic/silicone sensory phases | Primer migration, glissement excessif, reduced anchoring |
| Oil-in-water foundation | Water-continuous emulsion and mixed polymer system | Pilling, uneven wetting, localized drag |
| Water-heavy serum foundation | Low viscosity, rapid spreading, lighter pigment load | Uneven grip, streaking, primer film disturbance |
| Long-wear / high-film-former foundation | Fast film formation and transfer resistance | Localized fixation, irrégularité, levage |
| High-pigment matte foundation | Higher solids/powder load and faster dry-down | Caking, pore settling, zones sèches, reduced blendability |
One terminology item I’d keep clear for a Product Development team: “high-pigment matte foundation” is a performance category, not necessarily an emulsion architecture. Matte foundations can be water-in-silicone, oil-in-water or another system. So I document the architecture, and also the performance profile when I can.
The supplier formulation technology demonstrates how diverse these systems can be. Silicone emulsifiers can be designed for water-in-silicone color cosmetics, while other formulation systems are intended for oil-in-water foundations and pigment dispersion.
This is exactly why the INCI list alone is not enough for my compatibility matrix.
When I build this matrix for an actual project, I also want the reference foundations to represent the type of products the target customer really uses rather than simply selecting whatever samples happen to be available in the laboratory.
XIRAN Private Label Foundation Range
I Have a Tiered Matrix, Instead of Testing Everything Against Everything
A full matrix can grow very big very quickly. If I have three primers, six foundations, three sub-layer conditions and three application tools, I already have 162 combinations before I repeat anything.
Therefore I usually divide the work into two stages.
Tier 1 is a screening tool. I use representative foundation architectures and the most relevant application condition to identify obvious risks like pilling, severe sliding, uneven coverage or rapid lifting.
Tier 2 is confirmatory testing. After the formula survives the first screen, I take the challenge to other foundations, sunscreen conditions, application tools and wear times.
That makes development more efficient because I don’t take 12 hours to evaluate a sample that fails badly at minute one.
R.&D Protocol Standard: How I Would Run the Test
I lock the protocol for repeatability and then compare Sample A to Sample B. The amounts and environmental settings should be the same as the product and intended-use conditions of the brand, so I wouldn’t pretend one universal dose is good for every primer. The important thing is to have the same dose, substrate, waiting time and application technique between samples.
This is how my working protocol would look:
1. Set Up the Test Environment and Samples
I write down the batch number, the age of the sample, the storage conditions, the room temperature and the relative humidity. Primer and foundation should be evaluated under similar controlled conditions across repeat runs.
2. Standardization of Substrate or Sub-Layer
As a technical control I maintain a bare-skin or controlled substrate condition and then add a standardized moisturizer condition and a standardized broad-spectrum sunscreen condition. For the entire comparison I use the same formula, lot and amount of application.
3. Use a Fixed Dose of Primer on a Given Area
The quantity should be based on the intended consumer dose and, where possible, expressed as mass per area. I don’t let one technician apply “a pea-sized amount” one day and a different technician make a different call the next.
4. Measure the Dry-Down Profile at Intervals
À 30 seconds, 60 seconds and 180 seconds I evaluate tack, glisser, visible film uniformity, displacement under light touch and whether the formula has reached its desired finish.
5. Apply a Set Foundation Dose
I repeat the test with representative foundation architectures from the testing matrix, keeping the foundation amount fixed in each comparison.
6. Run the Application-Tool Challenge
Sponge, brush and fingers all give different friction and shear conditions, so I test all three if they are relevant to the brand. I standardize technician, number of passes, pressure, sponge condition and brush type as much as possible.
7. Score Immediate Compatibility
I measure pilling, drag, slide, lift, streak, irrégularité, coverage uniformity, pore settling and change in finish both immediately after application and after the foundation film has settled.
8. Run the Wear Analysis
I usually review the system again at 2 hours and 6 heures, with a 12-hour checkpoint if the product positioning or wear claim makes that relevant. I note separation, creasing, briller, migration of pigment, retention of coverage, accentuation of pores and visible flaking.
9. Repeat the Condition
I cannot consider a formula characteristic on the basis of one observation. In technical screening I conduct replicate runs and then confirm relevant finalists under human-use conditions appropriate to the intended claim.
10. Compare Against Acceptance Criteria Defined in Advance
The pass/fail rule should be in place before the team knows the result. Otherwise it is all too easy to start tweaking the standard because everyone likes one sample better than another.
That last point is more important than it sounds. A good compatibility protocol does more than just generate data; it prevents a development team from moving the goalposts during sample approval.
Sub-Layer Standardization: Bare Skin Is the Control, Not the Consumer Reality
A serious compatibility program would include at least three substrate conditions: a control condition, a moisturizer challenge and a sunscreen challenge.
The state of the sunscreen is especially important.
Primer and foundation can both work beautifully on bare skin, but act differently over a film-forming sunscreen. Le 2024 pilling study found that sunscreen was an important stage in observed pilling behavior, which reinforces why I don’t treat it as an optional afterthought in complexion-product development.
The goal isn’t to find one “perfect sunscreen” that makes the primer look good. The objective is to choose a stable reference product to apply the same challenge to all prototypes.
I might also add a richer moisturizer condition for a skincare-led brand because the target customer is probably going to use more emollient skincare before makeup. The bigger real-world challenge for a makeup-led audience could be sunscreen.
The sub-layer should follow the customer, not some arbitrary laboratory habit.
I Want a Dry-Down Curve, Not One Waiting Time
One of the most useful changes I can make to primer development is to no longer document only the final texture.
Par exemple, a gripping primer can behave very differently at 30 seconds, 1 minute and 3 minutes. It may be wet at 30 seconds. The tack may be at the desired level at one minute. At three minutes the film might be stiffer.
That evolution changes what happens when you put foundation on.
I therefore document at least tack, glisser, surface displacement and visible film state during the dry-down interval. A simple trained-panel test can be used for screening, but instrumented measurement can be useful when a brand is trying to quantify subtle differences between prototypes.
Research into cosmetic films has shown that tack can be measured mechanically by means of texture-analysis techniques rather than on the basis of subjective feel alone. For routine product-development work, cependant, I still want instrumental measurements to support—not replace—the application behavior the consumer actually experiences.
Surface Energy? Big Deal?
je le ferais’t put “measure surface energy at 30 seconds” into a standard bench SOP if the lab didn’t actually have the instrumentation and validated method to do it.
Surface energy and wettability are real, relevant variables in makeup adhesion. Published cosmetic research has used contact-angle measurements to investigate the affinity between model skin surfaces and makeup layers, and one study reported improved makeup-layer uniformity when the difference in surface energy between substrate and makeup layer was reduced. Study: Makeup Adhesion, Stability and Surface Energy
But this is an advanced instrumental measurement normally involving controlled films, known probe liquids and contact-angle analysis. Je n'en ai pas’t visually infer it from whether a primer “feels dry.”
For most product-development teams, je’d differentiate the methods:
Routine SOP: tack, glisser, film integrity, displacement and application behavior.
Advanced diagnostic work: contact angle, calculated surface energy, tribology, rheology or instrumental tack, if the failure mode justifies the additional investigation.
The distinction keeps the protocol technically credible.
Application Tool Shear Challenge: Sponge, Brush and Fingers Are Not the Same
I think compatibility testing gets a lot more realistic when I stop thinking of foundation application as one generic action.
A sponge mainly involves pressing and repeated movement over a short distance. Repeated directional shear can be produced by a brush. Fingers provide warmth, variable pressure and a very different contact surface.
These mechanical differences can reveal failures I might otherwise never observe when I gently spread the product once in the laboratory.
This is especially relevant for pilling.
The published pilling study found that application motion affected the observed pilling behavior, confirming that the problem has a mechanical component as well as a formulation component.
Parfois, for internal testing, je’ll call this an application-tool shear challenge, but I wouldn’t want to pass that phrase off as some well-established ISO method. The manual method is still semi-quantitative unless the pressure, velocity and number of strokes are carefully controlled.
If a project calls for better repeatability, a mechanical applicator, texture analyzer or tribology setup can move the assessment from “trained evaluator” toward objective measurement.
I do both for most beauty-brand projects: controlled lab methods to compare samples and human application to see if the result still makes sense in the real world.
What I Score Right After Foundation Application
I do not want the evaluator to write only “good” or “bad.” I use a predefined score system.
| Compatibility Metric | What I Am Looking For |
|---|---|
| Pilling | Rolls, flakes, crumbs or polymer/powder aggregation |
| Blendability | Ability to spread foundation without excessive drag |
| Sliding | Foundation moving across rather than anchoring to the primer |
| Lifting | Foundation or primer film being removed during application |
| Patchiness | Local areas of high/low pigment deposition |
| Coverage uniformity | Whether intended coverage remains visually even |
| Streaking | Directional pigment lines after brush/finger application |
| Pore settling | Pigment or powder concentrating in pores |
| Caking | Excessive visible solid build-up or dry texture |
| Finish change | Primer unintentionally shifting foundation matte/satin/radiant character |
| Tack after foundation | Residual stickiness that remains after the complete system is applied |
I tend to use a simple severity scale, Par exemple 0 = none and 4 = severe, but I don’t think the numbers themselves are as important as the definitions behind them.
Two evaluators should be able to differentiate between a Grade 1 trace defect and a Grade 3 obvious failure.
Most importantly, the team should determine before testing which defects are critical. Controlled tack would be fine in a gripping primer but visible pilling could be an immediate fail. A pore-blurring primer can take a little bit of a finish change but may not work if the foundation coverage is drastically reduced.
The scorecard should mirror the product brief.
Time-Course Wear: Compatibility Doesn’t End After 5 Minutes
A primer/foundation combo can look flawless immediately and be a flop a few hours down the road.
By the 2-hour mark, I’m usually looking for early signs of shine, local separation around the nose, pigment migration and whether the foundation has started to settle into pores or expression lines.
Normally, at 6 heures, the differences in sebum interaction, film flexibility and retention of coverage are more obvious. Par exemple, if the brand is developing a long-wear system, a 12-hour test can show if a formula that looked great for the first few hours eventually ends up creasing, inégal, lifting or too shiny.
Chemistry of film formers, poudres, rheology and interaction with sweat and sebum influence long-wear foundation performance. Surface-energy, contact-angle, rheological and optical measurements can also provide additional information when the project needs deeper instrumental analysis.
This is why I don’t hold the primer accountable for every wear failure. The protocol is designed to test if the combination works.
Failure Analysis – What Various Problems Usually Tell Me
This is where compatibility testing is a real boon for R&D. I don’t just want to know that Sample C failed; I want the failure pattern to tell me what to change.
| Failure Signature | What I Investigate First | Useful Confirmation Test |
|---|---|---|
| Pilling during rubbing | Film disruption, polymer/powder/elastomer load, incomplete dry-down, friction | Change waiting time and application shear while keeping formulas constant |
| Sliding foundation | Excess lubricity, residual emollient/silicone phase, insufficient primer set | Longer cure interval; compare lower-slip primer control |
| Foundation lifting | Primer film cohesion, foundation solvent/emollient interaction, excessive mechanical shear | Press vs brush application; evaluate primer alone after foundation removal |
| Patchy coverage | Non-uniform tack/wettability, fast local fixation, uneven primer film | Map application immediately and compare lower-tack control |
| Coverage thinning | Excessive spreading/lubricity or pigment mobility | Compare deposited coverage at fixed foundation dose |
| Caking / pore settling | Powder load, fast evaporation, insufficient film flexibility, dry substrate | Repeat over hydrated standardized substrate |
| Late separation | Sebum/sweat interaction, emulsion-film compatibility, foundation wear system | 2/6/12-hour controlled wear comparison |
| Excess shine | Oil/emollient load, sebum interaction, insufficient oil control | Instrumental gloss/sebum measurement if required |
Note on “Coacervation” and Pilling
I’d be cautious about saying the primer pilling is “hyaluronic acid or carbomer interacting with silicone via coacervation.”
It sounds technical but it’s too wide.
Complex coacervation is classically described as associative liquid-liquid phase separation involving oppositely charged macromolecular species and electrostatic attraction. That means I would not diagnose an ordinary primer/silicone compatibility failure as coacervation simply because a carbomer-containing formula pills. PubMed: Recent Progress in Complex Coacervation Science
This is not to say that charged-polymer interactions can never be involved in cosmetic incompatibility. They are able to. But I see a carbomer-containing primer balling over a silicone-rich layer and I don’t just assume coacervation without experimental evidence.
More defensible initial hypotheses for many primer/foundation failures include mechanical film disruption, polymer aggregation under friction, powder/elastomer build-up, incomplete dry-down or incompatible wetting behavior.
That language is less dramatic, but far more useful to a formulation team.
Identifying Pilling Issues
If I see pilling, first I ask: when does it happen?
When the primer pills alone in rubbing, I look at polymer load, elastomer level, powder structure, dry-down and rheology in the primer system.
If the primer is stable until the foundation is introduced, I look into the interface between those films.
If pilling happens only with sunscreen underneath, I consider the sub-layer as part of the failure mechanism.
Then I vary one variable at a time. Longer wait time, less mechanical shear, one reference foundation or removing the sunscreen challenge gives me so much more information than all-at-once reformulation.
The same logic applies to Product Development management: a controlled diagnostic experiment is less expensive than random sample iteration.
Diagnosing Sliding & Lifting
Sliding is nearly the opposite experience of too much grip.
A primer can create such a slick surface that the foundation spreads too far, coverage decreases, and pigment moves around as the user blends.
Special emphasis is given here to silicone-rich systems as some elastomer and silicone technologies are designed to generate smooth, dry or highly spreadable sensory profiles. That’s good for primers but the sensory target still has to work with foundation.
Donc, I do not just consider if the primer feels silky, but whether the foundation can build a stable film over it.
If a primer has a three-minute volatile dry-down time before the foundation stops moving, that’s good information. The brand can then determine if that application behavior is appropriate to the target consumer experience or if the formula needs to be tweaked.
Brands can also use existing primer directions as benchmark references when defining the compatibility challenge, rather than developing and evaluating each concept in isolation.
XIRAN Private Label Makeup Primer Range
Patchiness and Uneven Coverage Diagnosis
Patchiness often has me looking at the local differences in grip and wetting.
If a gripping primer dries very quickly, the foundation may set almost immediately in the first area it touches. The consumer then attempts to diffuse the pigment outwards but the first section has already been partly fixed.
This can result in visible high- and low-coverage zones.
Surface science plays a role in this. Cosmetic research has demonstrated that substrate and makeup-layer affinity and differences in surface energy can affect makeup uniformity and adhesion.
For day-to-day R&D though I usually start with a simpler experiment. Increase playtime, reduce tack, change the dry-down interval or compare application tools.
I only use advanced surface-energy analysis when the simple experiments do not explain the pattern.
What a Brand Brief Should Tell the Formulator Before Testing Begins
One of the simplest ways to decrease unnecessary sample iteration is to define compatibility expectations prior to the first primer sample being made.
A brand should never simply say:
“Works great under foundation.”
Which foundation environment does it matter?
Is the primer mainly being designed for water-heavy serum foundations? Long-wear formulas with high coverage? Liquid foundations with a high percentage of silicone? Powder foundations? Does the customer usually start with a broad-spectrum sunscreen? Is the primer for use with fingers or for professional makeup artists using brushes?
I would also like to know the target dry-down time, desired tack profile, finish and expected wear window.
With those variables in the brief, formulation development is a whole lot more focused.
I can design the formulation and compatibility matrix with the intended use in mind from the get-go, rather than Sample 1 → feedback → random adjustment → Sample 2 → new complaint.
That is also why I prefer to connect compatibility requirements to the broader product-development brief at the beginning of the project.
XIRAN Cosmetic Product Development Process: De l'idée au marché
My Approach to Internal QC and Compatibility Screening Program at XIRAN
Chez XIRAN Cosmétiques, when we develop a primer for a brand, I don’t want the compatibility testing to stop once the R&D team has approved one attractive laboratory sample.
The first step is to map the product brief to the target foundation environment. If the brand is creating a compelling primer for long-wear liquid foundations then I build the screening around that use case. If the primer is intended for silicone-heavy complexion make-up and it blurs pores, the matrix is different.
Once I have the lab sample in the right texture and sensory profile, I would run the compatibility screen against representative foundation systems and standardized sub-layers. Then failures such as pilling, excess slip, patchiness or lifting go back into formulation development, rather than being discovered post-production.
Once the formula is approved, the same compatibility logic should be re-checked during pilot/scale-up production. A formula may be “within specification” but a subtle change in viscosity, evaporation behavior or sensory profile can become perceptible when foundation is applied over it.
That is why I prefer to have an approved reference sample and compatibility record separate from the normal QC specifications. Viscosité, look and pH can tell me the batch is within the formula specification. The compatibility reference helps me to confirm that the batch still creates the makeup experience the brand approved.
That’s also where GMP and R&D have to be conceptually separated. OIN 22716 provides guidelines covering cosmetic production, contrôle, storage and shipment, but the standard explicitly states that it is not applicable to research and development activities. A primer/foundation compatibility program therefore has to be designed internally during development and then translated into appropriate production and QC controls as the product moves toward commercialization. OIN 22716:2007 Cosmetics — Good Manufacturing Practices
Brands evaluating whether a manufacturer is suitable for this type of project should therefore look beyond whether “primer” appears in a catalog and consider formulation capability, sample iteration, testing support and the manufacturer’s ability to reproduce the approved sensory result.
Private Label Primer Manufacturers for Beauty Brands | FERMÉ
My Input to the Final Compatibility Report
A Product Development manager should be able to look at the report months later and know exactly what was tested.
For each approved primer I would like to see the final record identify the primer batch, reference foundations, foundation architecture where known, sub-layer products, quantities, application tool, waiting intervals, environmental conditions, evaluator or panel, immediate compatibility results and time-course wear observations.
Photos should be taken with the same lighting, distance, camera settings and facial zones where possible.
I would document the failures too.
A compatibility report that only lists successful combinations is worth a lot less than a report that says:
“Acceptable for Foundation Architecture A under sunscreen challenge. Minimal pilling with Foundation B when applied at 30 seconds, resolved at 180-second primer dry-down. Sample C failed due to extreme lifting with brush application.”
And that knowledge is institutional knowledge.
It also gives the future formulation team something much more useful than “the old version was better.”
What Does “Pass” Even Mean?
Je n'en ai pas’t think there should be a universal score of compatibility for all primers.
Hydrating primer, high-grip primer and pore-blurring primer are different in terms of product objectives.
I define critical attributes and then test them instead. For gripping primer, adhesion to the foundation and controlled tack may be important. If you have a silicone blur primer, smoothness and coverage retention may be more important. Even optical distribution, for an illuminating primer, may be more important than absolute matte control.
I still use the same defect vocabulary—pilling, sliding, levage, irrégularité, settling and creasing—but the threshold of acceptability should be according to the product brief.
What I would never do is decide the cutoff after the team has already seen what sample it prefers.
This is not normal procedure. That’s post hoc rationalization.
Résumé
The biggest mistake I see in primer product development is not the wrong silicone or polymer selection. It is approving the formula under conditions that are too easy.
Bare skin is good for a control, but not the same as a customer with moisturizer, crème solaire, primer and a high-pigment foundation. One foundation does not represent a whole complexion category and a five-minute visual check does not tell me if the system will remain stable six hours later.
A useful primer and foundation compatibility testing protocol must therefore challenge the whole system: substrate, dry-down, foundation architecture, application shear and wear time.
As brands set these conditions out in the development brief, and manufacturers screen for compatibility before going into mass production, sample feedback becomes more specific, formulation decisions are easier to diagnose and the risk of finding basic layering problems after launch is much lower.
That’s ultimately what I want out of the protocol: not more testing just for testing’s sake, but better evidence before a brand commits to production.
Frequently Asked Questions About Primer and Foundation Compatibility Testing
1. Is there an official FDA or ISO standard for testing primer and foundation compatibility?
No single FDA or ISO protocol specifically defines how cosmetic brands must test primer/foundation compatibility. FDA states that it does not maintain a prescribed list of tests for every cosmetic product, while ISO 22716 covers manufacturing GMP rather than R&D activities. I therefore treat primer/foundation compatibility as a brand-defined internal development method that should be scientifically reasonable, documented and repeatable.
2. How many foundation types should I test against one primer?
I would rather test a smaller, deliberately selected architecture matrix than a large number of random commercial foundations. At minimum, I want the matrix to represent the foundation systems most relevant to the target customer, such as water-in-silicone, oil-in-water, water-heavy serum, high-film-former long-wear and high-pigment matte formats where appropriate. Once the primer passes the screening matrix, I can expand the confirmation set.
3. Should sunscreen always be included in primer compatibility testing?
If the target customer is likely to wear sunscreen under makeup, I think it should be part of the compatibility program. Le 2024 pilling study found that sunscreen application was an important stage in observed pilling behavior, making it a meaningful challenge condition rather than an irrelevant extra layer. I would still maintain a bare-skin control so I can distinguish an intrinsic primer problem from a sub-layer interaction.
4. How long should primer dry before foundation is applied during testing?
I do not believe one waiting time should be applied to every primer. Plutôt, I prefer predefined checkpoints such as 30 seconds, 60 seconds and 180 seconds so I can build a dry-down profile. A gripping primer may reach its intended tack at a different time from a silicone blur primer, and understanding that curve can reveal whether an apparent compatibility failure is actually a timing issue.
5. How many repeat tests are needed before approving a primer formula?
I would never call something a formula characteristic on the basis of one application. During screening, I want repeat runs under the same controlled conditions; finalists should then be confirmed under human-use conditions appropriate to the intended product positioning and claims. The exact number of replicates depends on the project and method, but the key principle is that the result should be reproducible rather than dependent on one evaluator or one application.
6. Does a cosmetic brand need surface-energy or tribology testing?
Not for every project. For routine R&D screening, a standardized evaluation of tack, glisser, film integrity, pilling, levage, coverage and application behavior is often much more actionable. Contact angle, surface-energy analysis, rheology, tribology or instrumental tack become useful when simpler diagnostic experiments cannot explain the failure or when the brand needs objective differentiation between closely matched prototypes. Research does support the relevance of surface-energy differences to makeup-layer adhesion and uniformity.
7. What should count as an automatic compatibility failure?
I define critical failures before the test based on the product brief. Visible pilling may be an automatic fail for almost any primer, while a small amount of controlled tack could be acceptable—or desirable—for a gripping formula. Severe lifting, major coverage loss, obvious patchiness or foundation migration would also concern me. The important part is that the acceptance threshold is written before the team knows which sample performed best.
8. Should compatibility testing be repeated after pilot or scale-up production?
Oui, I would re-check the approved compatibility behavior after pilot and scale-up production. A production batch can technically remain within specification while subtle differences in viscosity, evaporation, rheology or sensory profile change how foundation behaves over the primer. I also want an approved reference sample and compatibility record so later batches can be compared not only on pH, appearance and viscosity but also on the makeup experience the brand originally approved.
