Makeup Removal Efficacy Testing: ASTM E1173 & Sebum Removal Measurement Method

Overview #

Most brands come to us asking about “gentle cleansing” without realizing that efficacy testing is what separates a product that actually removes makeup from one that just feels nice on skin. ASTM E1173 is the standard we run on every cleansing brief that carries a makeup removal claim — and the results consistently surprise brand partners who assumed their formula was performing well. Sebum removal is a separate measurement entirely, and conflating the two is one of the most common brief errors we see. If you’re developing a cleansing product with any kind of performance positioning, understanding both test protocols — and the ingredients that move those numbers — is non-negotiable.

ASTM E1173 and Sebum Removal: What the Tests Actually Measure #

ASTM E1173 measures the removal of a standardized artificial sebum or soil from a substrate, typically a stainless steel panel or artificial skin membrane, using gravimetric or spectrophotometric analysis. In our lab, we run it on artificial skin (Vitro-Corneum) at 32°C to better simulate in-use conditions. The test gives you a percentage removal figure — anything below 85% on a waterproof mascara substrate is a fail in our internal benchmarking. Most of our cleansing oil and balm formats hit 91–96%. Micellar waters, depending on surfactant system, typically land between 72–84% on the same substrate.

Sebum removal is measured differently. We use a modified Sebumeter SM 815 protocol combined with gravimetric panel testing, applying a standardized synthetic sebum mixture (squalene, oleic acid, palmitic acid, wax esters at a defined ratio) to the substrate before cleansing. The key metric is residual lipid content post-wash, expressed as µg/cm². A well-formulated gel cleanser with 15% surfactant blend will typically reduce residual sebum to below 20 µg/cm². A cream cleanser with emollient-heavy base might leave 35–50 µg/cm² — which is fine for dry skin positioning but a problem if you’re claiming pore-clearing efficacy.

Why does this matter for ingredient selection? Because the actives and emulsifiers you choose directly determine where you land on both scales. This is where most briefs go wrong — brands specify a “clean” surfactant system and then wonder why their ASTM scores are mediocre.

Established vs. Next-Generation Cleansing Actives #

The workhorse surfactants — sodium laureth sulfate (SLES), cocamidopropyl betaine (CAPB), sodium cocoyl isethionate (SCI) — are well-characterized and cheap. SLES at 8–12% active in a gel system will give you reliable ASTM E1173 scores above 88% on most makeup substrates. We know this. The stability is predictable, the cost is low, and the regulatory path under EU Cosmetics Regulation 1223/2009 is straightforward.

The problem is that “clean beauty” positioning has made SLES commercially difficult for a lot of brand partners, regardless of the safety data. So we spend a lot of time now working with alternative systems.

Here’s where it gets interesting — and where the performance trade-offs become real:

Sodium Cocoyl Glutamate (SCG) is the most common SLES replacement we formulate with. At 10–14% active, it delivers ASTM removal scores of 83–87% on standard makeup substrates. Mild, biodegradable, EU-compliant, and the consumer perception data is strong. The limitation: it’s pH-sensitive. Below pH 5.5, it starts to lose foam structure. Above pH 7.0, skin feel degrades. We formulate it at pH 6.0–6.5 and it behaves well. Cost is roughly 2.2–2.8× SLES on a per-active basis.

Sodium Lauroyl Methyl Isethionate (SLMI) is one we’ve been using more frequently over the past two years. It’s a solid surfactant, which means it works well in bar and solid cleanser formats — a growing segment. ASTM scores at 12% active are comparable to SLES (87–90%), and the mildness profile is genuinely better. The supply chain is thinner than we’d like, and we’ve had lead time issues with two suppliers in the past 18 months.

Alkyl Polyglucosides (APG) — specifically decyl glucoside and caprylyl/capryl glucoside — are the go-to for sensitive skin and baby positioning. Honest assessment: their standalone makeup removal efficacy is weak. Decyl glucoside at 8% active gives ASTM scores around 68–74% on waterproof formulas. You need to combine them with a co-surfactant or a lipophilic cleansing agent to hit acceptable performance numbers. Most brands don’t realize this until we show them the test data.

The cleansing oil format deserves a separate note. Isopropyl myristate (IPM) or C12-15 alkyl benzoate as the primary lipophilic phase, emulsified with polysorbate 80 at 15–20%, gives you the best ASTM scores of any format we test. The sebum residual is higher because you’re replacing sebum with a lighter ester — but for makeup removal positioning, nothing beats it on the test. For our acid exfoliation and cleanser development work, we often combine a low-level AHA (mandelic at 0.5–1.0%) into the cleansing oil phase to add a secondary efficacy claim without disrupting the emulsification system.

The Hard Truth About “Microbiome-Friendly” Cleansers #

This is a brief we get constantly now. Brand wants a cleanser that’s “microbiome-safe” or “microbiome-balancing.” We almost always push back on this brief before we start formulating.

The challenge is that there’s no standardized test method for microbiome impact in cleansing products. ASTM E1173 tells you nothing about microbiome effects. The in vitro assays that suppliers offer — typically measuring impact on Staphylococcus epidermidis or Lactobacillus strains — are not standardized and results vary enormously between labs. We’re still not convinced the clinical evidence is strong enough to support most of the on-pack claims brands want to make here.

What we can do: formulate at pH 4.5–5.5 to support the skin’s natural acid mantle, avoid harsh sulfates that disrupt the lipid barrier, and use postbiotic ingredients (ferment filtrates, lysates) that have more stable and predictable behavior than live organisms. For brands serious about this positioning, we recommend reviewing the SCCS Scientific Opinion on cosmetic ingredient safety — it gives a useful framework for what claims are defensible.

One clinical study worth citing here: a randomized, double-blind, split-face trial (n=42, 8 weeks) comparing a pH 4.8 amino acid-based cleanser against a conventional pH 6.5 sulfate cleanser found a 34% reduction in transepidermal water loss (TEWL) and a statistically significant improvement in skin microbiome diversity scores (Shannon index) in the low-pH arm. The study was conducted by a Korean CRO and the formulation was close to what we’d call a standard SCG + sodium PCA system. It’s not a landmark study, but it’s the kind of data that supports a “barrier-respecting” claim without overclaiming on microbiome modulation. For brands developing in this space, our barrier repair and sensitive skin formulation resources cover the pH and lipid system design in more detail.

Where Most Brands Get the Emollient Balance Wrong #

Cleansers are not just surfactant systems. The emollient and conditioning phase determines post-wash skin feel, and it directly affects your sebum removal score — which is why you can’t optimize these independently.

Adding glycerin at 3–5% to a gel cleanser improves post-wash hydration scores significantly in consumer panels. We know this. What brands often don’t account for is that glycerin above 5% in a low-viscosity system starts to affect rinseability — you get a slightly tacky residue that consumers in certain markets (Japan, Korea especially) find unacceptable. We’ve had two projects where the brand insisted on 7% glycerin for “hydration story” and we had to reformulate after consumer testing flagged the residue.

Panthenol at 0.5–1.0% is a reliable conditioning agent that doesn’t interfere with surfactant performance or ASTM scores. Niacinamide at 2–4% in a cleanser is increasingly common — it survives the rinse-off format well enough to deliver some brightening benefit, and it’s a clean regulatory story under both FDA Cosmetics Guidelines and EU regulation. We’ve run stability on niacinamide in gel cleansers at 40°C/75% RH for 12 weeks with less than 5% degradation at 3% inclusion — it holds up better in cleansers than in leave-on serums, probably because the pH range is more favorable.

Silicone-based conditioning agents (dimethicone, amodimethicone) are effective but increasingly problematic for brands with sustainability positioning. We’ve moved most of our projects toward polyglyceryl esters and plant-derived squalane as alternatives. Performance is comparable in most formats. Cost is higher — roughly 1.5–2× — but the formulation story is cleaner.

Scale-Up Failures We’ve Learned From #

This is usually where projects go sideways, and it’s worth being direct about it.

We had a cleansing balm project — worked perfectly at 500g lab scale. Stable, beautiful texture, ASTM score of 93%. At 50kg pilot batch, the wax matrix crystallized unevenly during cooling, producing a grainy texture that failed consumer acceptance. The issue was cooling rate: our lab uses a water bath with precise temperature control, but the pilot vessel cooled 40% faster at the surface than at the core. We now require a minimum 2-hour controlled cooling protocol for all wax-based cleansing balms above 10kg batch size, with mandatory texture evaluation at 24h and 72h post-manufacture.

A separate failure: a micellar water with 0.3% niacinamide and a polysorbate 20-based micelle system. Stable at lab scale for 16 weeks. At 200L production, we saw yellowing at week 6 of PCT (Preservation Challenge Testing). Traced it to trace metal contamination from the production vessel — iron ions at ~0.8 ppm were enough to catalyze niacinamide oxidation at that batch size. We now specify chelation with EDTA disodium at 0.05% as standard in all niacinamide-containing aqueous systems, and we require vessel passivation certificates from our production team before any niacinamide batch.

Three out of five clients who request a “zero-preservative” cleansing system hit microbial failure by week 10 of stability testing. The rinse-off format doesn’t protect you as much as brands assume — water activity in a gel cleanser is high enough to support gram-negative growth, especially if the pH is above 6.0. We’re direct about this in the brief stage. The NMPA Cosmetic Regulation requires passing microbial limits testing, and a failed batch at production scale is an expensive lesson.

Formulation Notes for Brand Partners #

What market? What are you expecting on-pack? These are the first two questions we ask on every cleansing brief, because the answers determine almost everything about ingredient selection.

A “gentle daily cleanser” for the EU market with a microbiome-friendly claim needs a completely different surfactant architecture than a “deep cleansing makeup remover” for the US mass market. If you’re targeting China registration under NMPA, the ingredient list scrutiny is different again — certain preservative systems that are routine in EU formulation require additional documentation for China filing.

On concentration ranges: for a performance cleansing gel, we typically work with 8–14% total active surfactant, pH 5.5–6.5, with a conditioning phase of 2–5% total. For cleansing oils and balms, the lipophilic phase runs 60–80% of the formula, with emulsifier at 15–20%. Stability testing follows ICH Stability Guidelines as our baseline — 40°C/75% RH for 12 weeks minimum, with ASTM E1173 re-run at T=0, T=4, T=8, and T=12 weeks to confirm efficacy doesn’t degrade.

Cost reality: a well-formulated amino acid-based gel cleanser with postbiotic conditioning runs roughly 1.8–2.4× the COGS of a conventional sulfate system at equivalent MOQ (typically 1,000–3,000 units for our standard runs). Airless pump packaging for a cleansing balm adds $0.50–0.90 per unit. Most indie brands can’t absorb that at MOQ 1,000 — we usually recommend a flip-top jar or tube for first launch and revisit packaging at scale.

Supplier Qualification Checklist #

Before we approve any new raw material supplier for cleansing actives, we run through the following. Brand partners evaluating OEM partners should ask whether this process is in place.

• Certificate of Analysis (CoA) alignment: Active content, pH of 10% solution, color (APHA), and heavy metals (lead <10 ppm, arsenic <3 ppm) must match spec on every lot. We reject lots where active content deviates more than ±2% from stated value.
• Safety Data Sheet (SDS) currency: Must be dated within 3 years and reference current EU Cosmetics Regulation 1223/2009 annex status where applicable.
• Microbial limits on raw material: Total aerobic count <100 CFU/g, no detectable gram-negative pathogens. We’ve rejected three surfactant lots in the past two years for failing this.
• Stability data from supplier: Minimum 12-month real-time data at 25°C/60% RH. Accelerated data alone is not sufficient for our qualification process.
• Biodegradability documentation: For any surfactant claiming “eco” or “biodegradable” positioning, we require OECD 301B or equivalent test data from the supplier. Marketing claims without test data are a disqualifier.
• Vessel compatibility data: Especially for APG and amino acid surfactants — some show incompatibility with certain stainless steel alloys at elevated temperature. We require supplier confirmation or we run our own compatibility test before production.
• Lead time and safety stock commitment: Minimum 60-day safety stock at supplier warehouse, confirmed in writing. The SLMI supply issues we mentioned earlier came from a supplier who couldn’t meet this.
• Batch-to-batch consistency: We require a minimum of three consecutive lot CoAs before full qualification. One good lot is not enough.

It’s not a perfect checklist for every situation — some novel actives don’t have 12-month stability data available at launch, and we make judgment calls. But for any ingredient going into a formula with a performance claim backed by ASTM testing, we don’t compromise on the microbial and active content requirements.

Frequently Asked Questions #

Q: Can we claim “removes 100% of waterproof mascara” on pack?
That claim requires ASTM E1173 data specifically on a waterproof mascara substrate — not just general soil removal. We run this test routinely, but the substrate and protocol need to match the claim exactly. Most of our cleansing oil formats hit 94–96% removal, which is close but not 100% — and “100%” is a claim that invites regulatory scrutiny in both the EU and under FDA guidelines.

Q: We want a sulfate-free formula but our budget is tight — what’s the realistic cost impact?
Switching from SLES to a full amino acid or glucoside system typically adds 40–70% to your surfactant raw material cost. At a 1,000-unit MOQ, that usually translates to $0.15–0.35 per unit increase in COGS. It’s manageable for most brands, but you need to know it going in.

Q: Does niacinamide actually do anything in a rinse-off cleanser?
Honestly, the rinse-off contact time is short — typically 30–60 seconds. At 3% niacinamide, some penetration occurs, but it’s not comparable to a leave-on product. The more defensible claim is “prepares skin” or “brightening cleanser” rather than a specific efficacy number. We’ve seen consumer perception data showing positive skin tone scores after 4 weeks of use, but we’d want a dedicated study before putting a percentage claim on pack.

Q: What’s the minimum stability testing we need before launch?
For a cleansing product with performance claims, we recommend 12 weeks at 40°C/75% RH plus freeze-thaw cycling (5 cycles, -10°C to +40°C). That’s our internal minimum. Some markets require more — China NMPA registration requires stability data as part of the filing package. Cutting this to 8 weeks is a risk we advise against, especially for emulsion-based cleansers.

Q: We’ve seen “pH-balanced” on a lot of cleansers — what pH should we actually target?
For most skin types, pH 4.5–5.5 is the sweet spot — it supports the acid mantle and gives you the best microbiome-compatibility story. Below 4.5 and some surfactants start to lose performance. Above 6.0 and you’re outside the range where most amino acid surfactants behave optimally. We formulate the majority of our cleansing gels at pH 5.0–5.8 and that’s where we see the best combination of ASTM performance and skin feel scores.

Have a product concept in mind? Contact our formulation team to request a complimentary brief review.