50ml full size, 15ml travel size
ESK · Vitamin C serum
C Forte
ESK C Forte · a 16% L-ascorbic acid morning serum with vitamin E and ferulic acid
A morning antioxidant serum built on L-ascorbic acid 16%, the pure form of vitamin C, with vitamin E 1% and ferulic acid 0.5%, at pH 2.5 to 3.5 in airless, opaque packaging so it stays active. For the look of brighter, firmer, more even-toned skin. Suitable for most skin types, including deeper skin tones (Fitzpatrick V to VI); ESK does not recommend it for sensitive or acne-prone skin.
- L-ascorbic acid 16%, the well-studied form of vitamin C, with ferulic acid and vitamin E, the classic stabilising trio.
- Airless, opaque pump at pH 2.5 to 3.5, so it stays clear and active rather than turning brown in the bottle.
- One morning step before moisturiser and SPF, and a natural partner to a pigmentation routine.
- Not for sensitive or acne-prone skin, per ESK: the strength and low pH can sting or worsen breakouts. C Lite is the gentler option.
Not sure your skin will take 16%? Try the 15ml first for £35
The travel size lasts 3 to 4 weeks, long enough to know whether a strong vitamin C suits you. If it stings, C Lite at 10% is the same idea at a gentler strength.
Free UK delivery over £65 · Tracked £3.49 · Sent tracked, 2 to 4 working days
- Good to know
- ESK says a slight scent from the ferulic acid can be noticed and fades after application. Vitamin C oxidises over time: if the serum turns brown it has lost its activity.
- Stockist
- Melatone Skin Clinic is an authorised ESK stockist. Genuine product with full traceability.
If it stings or tingles for more than a few seconds, your skin is telling you 16% is too strong for it. Rinse off, and switch to C Lite. Skin that is breaking out should also skip it, per ESK.
Not sure if this is right for your skin? Message us on WhatsApp or book a skin assessment and we will confirm the right routine first.
A 16% vitamin C serum, honestly
Most people who reach for a vitamin C want brighter, less dull skin and some help with uneven tone, and want to know the serum actually works rather than having oxidised in the bottle. C Forte answers both: L-ascorbic acid at 16% with the ferulic acid and vitamin E that the best-known studies pair it with, and airless, opaque packaging so it stays clear.
What it will not do is suit everyone. ESK is explicit that the strength and the low pH can sting sensitive skin and can aggravate breakouts, and that people with occasional hormonal spots should avoid the affected areas. That is not a reason to skip vitamin C; it is a reason to pick C Lite instead.
In a pigmentation routine, vitamin C works on a different part of the pigment pathway from 4-n-butylresorcinol, which is why we pair it with Enlighten Gold in the morning. It is a supporting step: the tone-evening active, daily SPF and time do the heavy lifting.
Quick facts
- What it is
- A morning antioxidant serum with pure vitamin C.
- Sizes
- 50ml (£69.00, around 3 to 4 months) and 15ml travel size (£35.00, around 3 to 4 weeks).
- Best for
- The look of dullness, uneven tone and loss of firmness; a morning partner to a pigmentation routine.
- Skin types
- Normal, combination, dry and mature skin, including deeper skin tones (Fitzpatrick V to VI). Not for sensitive or acne-prone skin, per ESK.
- Key ingredients
- L-ascorbic acid 16%, vitamin E 1%, ferulic acid 0.5%.
- pH
- 2.5 to 3.5, the range at which L-ascorbic acid stays active.
- Packaging
- Airless, opaque pump to slow oxidation.
- How to use
- 1 to 2 pumps, morning only, after cleansing and before moisturiser and SPF.
- Daily SPF
- Required. Vitamin C supports SPF; it does not replace it.
- Free from
- Parabens and sulphates.
Where it fits in a morning routine
Morning: cleanse with Calming Cleanse, then C Forte, then your moisturiser, then SPF such as Zinc Shade.
For pigmentation: cleanse, C Forte, Enlighten Gold, then Zinc Shade. Vitamin C and 4-n-butylresorcinol work on different parts of the pigment pathway. The full set is the Pigmentation Kit.
Night: vitamin C is a morning product. Retinals such as Ultimate A Gold go on at night, on the same day without a problem.
The detail
Ingredients, and what each one does
- L-ascorbic acid (vitamin C), 16%
- The pure, best-studied form of vitamin C. An antioxidant that helps neutralise the free radicals generated by UV and pollution, and is studied for the look of brightness, firmness and a more even tone. It needs a low pH and protection from air and light to stay active. Widely studied.
- Ferulic acid, 0.5%
- A plant antioxidant that helps stabilise L-ascorbic acid and extends its protection. The source of the faint scent ESK mentions. Widely studied.
- Vitamin E (tocopherols), 1%
- An oil-soluble antioxidant that works alongside vitamin C. The C, E and ferulic combination is the one the reference studies used. Widely studied.
- Glycerin, propanediol
- Humectants and solvents that carry the vitamin C and keep the serum comfortable.
- Soybean oil
- A light emollient included in the formula.
Ascorbic acid 16%, tocopherol 1% and ferulic acid 0.5% as printed on the ESK pack; pH 2.5 to 3.5 as published by ESK. Descriptions are about the look and feel of skin, not a medical outcome.
Full ingredients (INCI): Glycerin, Water/Aqua, Propanediol, Ascorbic Acid, Butylene Glycol, Ethoxydiglycol, Tocopherols, Glycine Soja (Soybean) Oil, Phenoxyethanol, Polyacrylate Crosspolymer-6, Ferulic Acid, 2-methylpropan-2-ol.
How to use it
Morning
- Cleanse and pat dry.
- Put 1 to 2 pumps of C Forte on your fingertips and smooth over the face.
- Let it settle for a minute.
- Follow with your moisturiser, then SPF.
Beyond the face
It can also be used on the décolletage, the backs of the hands and the forearms.
Starting out
If you have not used a strong vitamin C before, start every other morning for the first week. A brief tingle can happen; stinging that lasts means it is too strong for your skin.
Night
Not for night use, per ESK. Keep it as your morning step.
What to expect, and when
- First use
- A light serum that absorbs quickly. A faint scent from the ferulic acid fades after application.
- 2 to 4 weeks
- Skin often looks brighter and less dull.
- 8 to 12 weeks
- The point to judge the look of tone and firmness.
- If it turns brown
- The vitamin C has oxidised and lost its activity. Keep the pump closed and out of light; the airless bottle is designed to slow this.
Is it right for my skin
- Normal, combination and dry skin
- Yes.
- Mature skin and loss of firmness
- Yes. This is a core use.
- Dull or uneven-looking tone
- Yes, alongside SPF and, for marks, a tone-evening active.
- Deeper skin tones (Fitzpatrick V to VI)
- Yes.
- Sensitive or reactive skin
- No, per ESK. Choose C Lite.
- Acne-prone skin
- No, per ESK: the strength and low pH may aggravate breakouts. Occasional hormonal spots: avoid the affected areas, or use C Lite.
- Rosacea-prone skin
- Not recommended. A low-pH vitamin C is a common trigger.
- Pregnancy or breastfeeding
- Topical vitamin C is widely regarded as suitable; ESK publishes no specific guidance. Ask your midwife, GP or pharmacist if unsure.
Using it with what you already own
- Enlighten Gold
- Yes. C Forte first, then Enlighten Gold, then SPF.
- Niacinamide
- Yes. The old advice to keep them apart came from conditions that do not apply to modern formulas.
- Retinal or retinol
- Yes, on the same day: vitamin C in the morning, the retinal at night.
- Exfoliating acids
- Not in the same routine. C Forte is already at a low pH; keep acids for the evening and watch for irritation.
- Hyaluronic acid serum
- Yes. C Forte first (it is the lower-pH, thinner step), then the hyaluronic serum, then moisturiser.
- SPF
- Always. Vitamin C supports sun protection; it does not replace it.
- After in-clinic treatments
- Pause it for as long as your practitioner advises after a peel, microneedling or laser: low-pH serums sting on healing skin.
Questions we actually get asked
What is ESK C Forte?
A morning antioxidant serum with L-ascorbic acid 16%, vitamin E 1% and ferulic acid 0.5%, at pH 2.5 to 3.5, in an airless, opaque pump. It is ESK's stronger vitamin C; C Lite is the 10% version.
What does vitamin C serum do?
Vitamin C is an antioxidant that helps neutralise the free radicals generated by UV and pollution. In skincare it is studied for the look of brightness, firmness and a more even tone. It supports sun protection but does not replace SPF.
Is it good for hyperpigmentation?
It works on a different part of the pigment pathway from tone-evening actives such as 4-n-butylresorcinol, which is why we pair it with Enlighten Gold in the morning. On its own it is a supporting step; the tone-evening active, daily SPF and time do most of the work.
Why L-ascorbic acid and not a vitamin C derivative?
L-ascorbic acid is the form with the most evidence behind it. It is also the least stable, which is why C Forte is formulated at a low pH with ferulic acid and vitamin E, and packed in an airless, opaque pump.
When should I use a vitamin C serum?
In the morning, after cleansing and before moisturiser and SPF. ESK says C Forte is not for night use.
How do I use it?
1 to 2 pumps on clean, dry skin in the morning. Let it settle for a minute, then moisturiser and SPF.
Vitamin C or hyaluronic acid first?
C Forte first. It is the thinner, lower-pH step; a hyaluronic serum goes over it, then moisturiser.
Can I use vitamin C with niacinamide?
Yes. Enlighten Gold, B Calm and Repair + all contain niacinamide and go over C Forte without a problem.
Can I use vitamin C with retinol or retinal?
Yes, on the same day. Vitamin C in the morning, the retinal at night.
Can I use it with exfoliating acids?
Not in the same routine. C Forte is already at pH 2.5 to 3.5. Keep acids for the evening and watch for irritation.
Does it sting?
A brief tingle on application can happen with a low-pH vitamin C. Stinging that lasts, or redness afterwards, means it is too strong for your skin; switch to C Lite.
Is it suitable for sensitive skin?
No. ESK does not recommend it for sensitive skin. C Lite is the gentler option.
Is it suitable for acne-prone skin?
No, per ESK. The strength and low pH may aggravate breakouts. If you get occasional hormonal spots, avoid the affected areas, or use C Lite.
Is it suitable for deeper skin tones?
Yes. It is suitable for deeper skin tones (Fitzpatrick V to VI). If your skin is reactive, start with C Lite, because irritation on deeper skin can leave marks.
Can I use it in pregnancy or breastfeeding?
Topical vitamin C is widely regarded as suitable in pregnancy, and ESK publishes no specific guidance. If in doubt, ask your midwife, GP or pharmacist.
Why does it smell?
ESK says some people notice a slight scent from the ferulic acid, which fades quickly after application. It is not a fragrance ingredient.
Why has my vitamin C turned brown?
L-ascorbic acid oxidises when exposed to air and light, and turns from clear to yellow to brown as it loses activity. C Forte's airless, opaque pump is designed to slow that. If it has turned brown, it is time for a new bottle.
How should I store it?
Pump closed, out of direct light, away from heat. Do not decant it into another container.
How long does it take to work?
Skin often looks brighter within 2 to 4 weeks. The look of tone and firmness takes 8 to 12 weeks of daily use.
Does vitamin C replace sunscreen?
No. It supports sun protection by dealing with some of the free radicals UV creates, but it does not block UV. Wear SPF every morning.
What is the difference between C Forte and C Lite?
C Forte is L-ascorbic acid 16% with vitamin E and ferulic acid, for skin that can take a strong vitamin C. C Lite is L-ascorbic acid 10% in a lighter, non-greasy formula, for sensitive, oily or acne-prone skin.
Is it a good vitamin C serum for mature skin?
Yes. Loss of firmness and dullness are the concerns ESK positions it for, and the C, E and ferulic combination is the one the reference studies used.
Can I use it on my neck and hands?
Yes. ESK says it can be used on the décolletage, the backs of the hands and the forearms.
Does it contain fragrance?
No fragrance ingredient is listed. The faint scent comes from the ferulic acid. It is free from parabens and sulphates.
How long does a bottle last?
The 50ml lasts around 3 to 4 months of daily morning use. The 15ml travel size lasts around 3 to 4 weeks.
Is it cruelty free and vegan?
Yes. ESK states that C Forte is cruelty free and vegan.
Is Melatone an authorised ESK stockist?
Yes. Melatone Skin Clinic is an authorised ESK stockist. Stock comes directly from ESK, so every item is genuine and traceable, and it is the same product we use in clinic.
Can someone help me work out whether this is right for me?
Yes. Message us on WhatsApp with a description of your skin, or book a skin assessment at the clinic in Battersea.
What is the delivery and returns position?
Tracked UK delivery is £3.49, or free over £65, and usually arrives in 2 to 4 working days. Sealed, unopened items can be returned within 60 days for a refund.
Buying it from Melatone
Melatone Skin Clinic is an authorised ESK stockist. Stock is bought directly from ESK, so every item is genuine and traceable, and it is the same product we use in clinic in Battersea, London.
If you are not sure this is the right vitamin C for your skin, do not guess. Message us on WhatsApp or book a skin assessment, and we will suggest a routine before you buy.
Delivery
Tracked UK delivery, £3.49 or free over £65. It usually arrives within 2 to 4 working days, with tracking by email. The price you see is the price you pay, with any delivery charge shown in full before checkout.
Returns
Sealed, unopened items may be returned within 60 days of receiving your order for a refund. For hygiene reasons we cannot accept returns of skincare once any seal has been opened, unless faulty. Your statutory 14-day right to cancel is unaffected.
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