Customers question bottle fill level, unaware of necessary airspace for safe vitamin C oxidation prevention per manufacturer guidelines.

Reviewers initially complain about bottle capacity until learning the vacant space intentionally prevents oxidation and gas-related risks through proper shaking technique.

This review is from Amazon.com for product:

COSRX Pure Vitamin C 13% Serum with Vitamin E & Hyaluronic Acid, Hydrating Facial Serum for Fine Lines, Uneven Skin Tone & Dull Skin, 0.67fl.oz/20ml, Korean Skin Care

Everyone keeps complaining about the amount in the bottle. If you read the manufacturer website about storing and handling it specifically says extra room added to the bottle for safe use. Gas can be generated therefore the room in the bottle has a purpose. Gently shake bottle.

Vitamin Basics & Tips

Vitamin C (ascorbic acid) formulations require special handling due to their chemical instability. The empty space in serum bottles serves multiple purposes: it accommodates gas release from decomposition reactions, minimizes oxygen exposure to slow oxidation, and allows proper mixing when shaken. L-ascorbic acid solutions gradually degrade when exposed to light, heat, and air – a process accelerated in completely full containers due to pressure changes.

Proper storage in cool, dark environments helps maintain potency. Some manufacturers use amber bottles and airless pumps to extend shelf life. When vitamin C oxidizes (turning dark yellow or brown), it becomes less effective but not harmful. Users should shake bottles gently to redistribute settled particles without introducing excessive oxygen through vigorous motion.

Daily vitamin C serum application helps combat free radicals, boosts collagen production, and brightens skin tone. Pairing it with vitamin E and ferulic acid enhances stability and efficacy. For optimal results, apply to clean dry skin before moisturizers and always follow product-specific storage instructions to preserve antioxidant properties.

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Repeat buyer praises vitamin C serum: brightens skin, reduces wrinkles, gentle formula, no odor, great value.

Beloved vitamin C serum delivers brighter skin, reduces wrinkles, non-irritating formula with neutral scent at affordable price point.

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Mild smell, tolerable taste, no side effects; texture varies by mold shape – will repurchase original version.

No adverse effects despite unusual odor; easy daily intake with acceptable taste. Texture depends on mold type – reordering preferred version to compare.

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Tags： vitamin c oxidation serum bottle design product storage guidelines gas formation prevention ascorbic acid stability

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