5 Stability Tests Korean ODM Labs Run Before a Formula Ships
Quick Answer
Before a formula leaves a Korean ODM lab, it passes through five stability tests: accelerated aging at 40°C/75% RH, freeze-thaw cycling, microbiological challenge testing under ISO 11930, packaging compatibility screening, and photostability evaluation. Each test targets a different failure mode. Skip one, and you risk a recall, a retailer chargeback, or a product that falls apart on a shipping container crossing the Pacific.
You found a Korean ODM. You locked in a formula you love. Samples look great on your bathroom shelf. But between that sample and a production run sits a gauntlet most indie founders never see: the stability testing phase.
Korean ODM labs take this phase seriously. The country's cosmetics industry built its global reputation on consistency, and the testing protocols reflect that. These are not optional add-ons. They are the reason Korean-manufactured products hold up in Houston humidity and Minnesota winters alike.
Here are the five stability tests your formula will go through before it ships, what each one actually measures, and why you should care about every single one.
1. Accelerated Aging (Thermal Stress Testing)
Accelerated aging is the backbone of any stability program. The idea is simple: subject the formula to elevated temperature and humidity so that months of shelf life can be predicted from weeks of lab data.
Korean ODM labs typically follow protocols aligned with ICH Q1A(R2) guidelines, adapted for cosmetics. The standard conditions are 40°C ± 2°C at 75% ± 5% relative humidity, held for three to six months. Some labs also run a parallel set at 50°C to stress-test the upper limits of the formula. Long-term stability samples sit at 25°C/60% RH and are checked at 0, 3, 6, 9, and 12 months.
At each interval, technicians measure pH, viscosity, color, odor, and active ingredient concentration. A serum that starts at pH 5.5 and drifts to 4.2 after eight weeks at 40°C is telling you the formula will degrade on a retail shelf within a year. A cream that thins out under heat signals emulsion instability that will show up as phase separation in real-world storage.
For founders working with active-heavy formulas (think retinol, retinal, or L-ascorbic acid), accelerated aging data is especially critical. These ingredients are inherently unstable, and the test will reveal whether your chosen stabilization system actually works at scale.
What to ask your ODM: Request the full accelerated aging report with data at each time point, not just a pass/fail summary. You want to see the trend lines. A formula that "passes" but shows a steady downward drift in active concentration is a formula you should reformulate before committing to a production run.
2. Freeze-Thaw Cycling
Your product will travel. It will sit in a shipping container that hits 45°C crossing the equator, then land in a cold-chain warehouse at 5°C. If it ships during winter, it might freeze in a delivery truck overnight. Freeze-thaw testing simulates exactly this kind of temperature whiplash.
The standard protocol cycles samples between -10°C (24 hours) and 45°C (24 hours), with a return to room temperature between each swing. Most Korean ODMs run a minimum of three full cycles, though five or more is common for products destined for markets with extreme climates.
After each cycle, the lab checks for phase separation, crystallization, texture changes, color shifts, and changes in viscosity or pH. An emulsion that creams or cracks after two cycles will not survive a supply chain that spans Seoul to Los Angeles.
This test is particularly important for emulsions, suspensions, and any formula containing waxes or butters that can crystallize at low temperatures. If your product is a lightweight gel or toner, it may breeze through. If it is a rich cream with shea butter and beeswax, freeze-thaw is where hidden instability shows up.
One thing founders overlook: freeze-thaw results also affect your compliance documentation. Retailers and distributors increasingly ask for stability data that includes temperature cycling, especially for products sold through e-commerce channels where climate control during shipping is unpredictable.
3. Microbiological Challenge Testing (ISO 11930)
A formula that looks and feels stable can still be microbiologically unsafe. Challenge testing, governed by ISO 11930, answers one question: does your preservative system actually work?
The test involves deliberately inoculating the product with five reference microorganisms at standardized concentrations: Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, Candida albicans, and Aspergillus brasiliensis. These cover gram-negative bacteria, gram-positive bacteria, yeast, and mold. The lab then measures microbial reduction at defined time intervals (typically days 2, 7, 14, and 28) to determine whether the preservative system can suppress contamination to acceptable levels.
Korean ODMs often run this test alongside the Korean MFDS's own microbiological specifications, which set limits for total aerobic counts and prohibit specific pathogens in finished cosmetics. Products that fail either standard go back to formulation.
For indie founders, the challenge test is especially relevant if you are formulating with "clean" or "preservative-free" positioning. Natural preservation systems built on ingredients like glyceryl caprylate or ethylhexylglycerin can work, but they require careful concentration balancing. The challenge test is where you find out whether your natural system holds up against real-world contamination scenarios, or whether it is just marketing copy.
What to ask your ODM: Confirm they test per ISO 11930 criteria A (the stricter standard) rather than criteria B. Criteria A requires a greater log reduction and is the benchmark most EU and US retailers expect.
4. Packaging Compatibility Testing
A stable formula in a glass beaker can become an unstable product in the wrong container. Packaging compatibility testing evaluates how your formula interacts with its primary packaging over time.
The lab fills your chosen containers (airless pumps, dropper bottles, tubes, jars) with the formula and stores them under the same accelerated conditions used in thermal stress testing. At each time point, they check the product for changes in color, odor, pH, viscosity, and active concentration, but they also inspect the packaging itself. Are the seals intact? Has the pump mechanism corroded? Is the label adhesive lifting? Has the plastic leached anything into the formula?
Migration testing is a key component here. Certain plastics (particularly PET and some HDPE grades) can interact with specific actives or fragrance compounds, pulling ingredients out of solution or releasing plasticizers into the product. Korean ODMs test for this because Korean and EU regulations both set limits on extractables from cosmetic packaging.
This test is also where you discover practical problems. An airless pump that works perfectly with a water-weight serum may fail with a thicker cream because the viscosity exceeds the pump's draw capacity. A matte-finish tube may absorb fragrance compounds from the formula, leaving the product smelling flat after three months on shelf.
If you are importing finished goods to the US, packaging compatibility data also supports your MOCRA facility registration and product listing requirements, demonstrating that you have verified the safety of the product as packaged, not just as formulated.
5. Photostability Testing
Light degrades cosmetic ingredients. UV exposure breaks down retinoids, oxidizes vitamin C derivatives, fades colorants, and can destabilize emulsion systems. Photostability testing measures how your formula responds to controlled light exposure.
The protocol typically exposes samples to a defined dose of UV and visible light (following ICH Q1B guidelines adapted for cosmetics) and then measures changes in appearance, active concentration, pH, and odor. Some Korean ODMs also run photostability on the packaged product to test whether the container provides adequate light protection.
For sunscreen products, photostability takes on additional regulatory significance. Korean MFDS requires that SPF and PA claims be validated through standardized testing, and formulas using UV filters that degrade under light exposure (like avobenzone without a photostabilizer) will fail. The agency published draft amendments in August 2026 that would allow certain in vitro methods for SPF and PA determination, but the underlying stability requirement remains: your UV protection must hold up under real-world light exposure.
Even if you are not making a sunscreen, photostability matters. A vitamin C serum that turns brown after two weeks on a bathroom counter will generate returns and negative reviews. A tinted moisturizer whose pigments shift under fluorescent retail lighting will look different in-store than it did in your product photos.
What to ask your ODM: If your formula contains light-sensitive actives, request photostability data on both the bulk formula and the finished packaged product. The packaging should be part of the stability story, not an afterthought.
What This Means for Your Timeline
Stability testing is the longest single phase in the Korean ODM manufacturing process. Accelerated aging alone takes three to six months. Challenge testing runs about 28 days. Packaging compatibility overlaps with accelerated aging but adds its own checkpoints.
Total timeline from formula lock to full stability clearance: roughly three to six months, depending on the product category and your ODM's lab capacity. Some ODMs will begin production after the three-month accelerated data clears, running long-term stability in parallel with your first production batch. Others require full six-month data before releasing a batch for sale.
Plan for this. If you are targeting a Q1 retail launch, your formula needs to enter stability testing by the previous summer at the latest. Building this timeline into your launch planning prevents the panicked shortcuts that lead to products with insufficient stability data on the market.
The best Korean ODMs will walk you through every report, explain what each data point means, and flag concerns before they become production problems. If your ODM hands you a one-page pass/fail summary and resists sharing the raw data, that is a signal to ask harder questions. For a deeper dive into reading these reports, see our guide on reading ICH and ISO stability reports.
I'm Liz, founder of altameet. I've sat in Korean ODM labs reviewing stability reports with founders who had no idea what they were looking at. Understanding these five tests gives you the vocabulary to ask the right questions and the confidence to push back when something looks off. Book a free gut-check call if you want to talk through your next move.
Free K-Beauty Brand Launch Checklist
From stability testing protocols to FDA compliance and retail-ready packaging.
