C-Firma Fresh Day Serum
Reviewed by SerumTruth Editorial · Price and formula checked July 2026
The mix-it-yourself format is a real answer to the oxidation problem that dogs L-ascorbic acid, and the antioxidant trio has strong evidence behind it. You pay a prestige price and you have to use it within a few months of mixing. For a fresh, well-packaged 15% vitamin C, it delivers.
- Air- or light-sensitive actives in protective, opaque packaging
- Costly to use, about $50 a month
- Evidence24 / 30
Strength of the research behind the key actives
- Vitamin C (L-Ascorbic Acid): strong evidence
- Vitamin E (Tocopherol): moderate evidence
- Ferulic Acid: moderate evidence
The average of the key actives’ evidence grades.
- Potency21 / 25
Dosed at studied levels, not fairy-dusted
- Vitamin C (L-Ascorbic Acid) (15%): dosed at a studied level
- Vitamin E (Tocopherol): dosed at a studied level
- Ferulic Acid: dosed at a studied level
How strongly the actives are dosed, led by the strongest, not how many there are.
- Delivery & stability16 / 20
Delivery tech + packaging that protects fragile actives
- Delivery: standard
- Packaging: airless, opaque
- Air- or light-sensitive actives (Vitamin C (L-Ascorbic Acid), Vitamin E (Tocopherol), Ferulic Acid), so packaging is scored.
Delivery tech plus packaging, and packaging only counts when actives are fragile.
- Formulation7 / 10
Disclosure, active breadth, and ingredient generation
- 1 of 3 actives disclose a concentration
- 3 key actives (breadth credit caps at 3)
- Current-generation or synergistic: Vitamin C (L-Ascorbic Acid), Vitamin E (Tocopherol), Ferulic Acid
Disclosure, active breadth, and current-generation or synergistic actives.
- Value5 / 15
What a month of use costs vs. the category
- About $50 per month to use
- $78 for 28 ml, used about twice a day (about 0.3 ml each time), so a bottle lasts about 1.6 months
What a month of use costs: full marks at $6 a month or less, the floor at $60 a month or more.
Tap any row to see how its score was built.
Ranks #13 of 27 vitamin c & antioxidants serums we have scored.
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What’s inside
| Active | Disclosed | Dose |
|---|---|---|
| Vitamin C (L-Ascorbic Acid) | 15% | Studied |
| Vitamin E (Tocopherol) | n/a | Studied |
| Ferulic Acid | n/a | Studied |
A two-part fresh-mix system: you pour the liquid base into a vial of 15% L-ascorbic acid powder and shake before first use, so the vitamin C is not sitting pre-dissolved and oxidising on the shelf. Vitamin E and ferulic acid round out the antioxidant side, and the mixed serum lives in an opaque pump. Once activated it is meant to be used within about six months.
How it’s delivered
Air- and light-sensitive actives (vitamin C, copper peptides) lose potency fast in the wrong packaging, so delivery and the bottle are scored, not just what’s on the label.
The actives, explained
What the research says
A 6-month double-blind trial found topical vitamin C linked to a better looking global appearance of photoaged skin versus placebo.
Topical ascorbic acid on photoaged skin. Clinical, topographical and ultrastructural evaluation: double-blind study vs. placebo. Experimental Dermatology, 2003. PubMed ↗
A dermatology review describes topical vitamin E as an antioxidant linked to smoother, better moisturized looking skin in limited human studies.
Vitamin E in dermatology. Indian Dermatology Online Journal, 2016. PubMed ↗
A study of the active, not this exact product. What matters for the score is whether this serum uses it at a comparable dose.
Higher-scoring alternatives
Same category, better SerumProof score. Worth a look before you buy.
Revision history
- July 11, 2026Price and formula rechecked
- July 10, 2026Review published
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Cosmetic information for general education, not medical advice. The SerumProof score reflects our reading of publicly available research and formulation disclosures. See how scoring works.