ISO 11930 is the international standard for evaluating the antimicrobial protection of a cosmetic product. The test inoculates your formula with bacteria, yeast, and mold at set concentrations, then measures microbial reduction over 28 days. Natural preservation systems often require more careful tuning to pass because they are narrower-spectrum than synthetic alternatives. Any cosmetic formulator you hire for a natural preservation project should treat challenge testing as a mandatory deliverable, not optional.
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