Getting the most from your vitamin C serum

Fresh vitamin C is only as good as how you use and store it. Here's how to choose your strength, apply your NuFountain serum, and keep it potent.

Choosing your strength

New to vitamin C or sensitive? Start with C10 (10%). Comfortable with actives? C20 Original is the simple classic, C20 Ferulic is our bestseller, and C20 Brightening targets dark spots with added niacinamide. If L-ascorbic acid irritates your skin no matter what, C15 MAP is the gentle alternative.

How to apply

Start with clean, dry skin. Apply sparingly — 5–6 drops is plenty for the whole face — smooth it in, and let it dry for a minute before your next step. Vitamin C goes on before moisturizer, sunscreen, and makeup. A mild, warm tingle is normal in the first week or two; if you feel real stinging or see persistent redness, reduce how often you use it or switch to a gentler strength.

When to use it

Use it in the morning. Vitamin C is an antioxidant, so it does its best work during the day — the hours when UV light and pollution generate the free radicals it helps neutralize. Applying it in the morning also puts it in the same routine as your sunscreen, and those two work as a pair: the serum builds your results, the SPF protects them. Keeping it to one consistent morning step is also the easiest way to actually stay consistent, which is what drives results. Many people notice changes in tone and texture building gradually over about 6–8 weeks.

The order of your routine

1. Cleanse
2. Vitamin C serum (let it dry)
3. Moisturizer
4. Sunscreen — the step that protects everything underneath

How to store it (the important one)

Freshness is the whole point of NuFountain, and storage keeps it that way. Keep unopened bottles in the refrigerator, where they stay potent for months — check the hand-written made-on date anytime. Once opened, keep the bottle tightly capped in a cool, dark place, away from sunlight and steam. L-ascorbic acid oxidizes slowly with air, light, and time: if your serum ever turns dark amber, it's past its prime — replace it.

Patch testing and sensitive skin

If you're new to active ingredients or have reactive skin, patch-test first: apply a small amount to your inner forearm for a few days before using it on your face, and start with our gentler C10 two or three mornings a week, building up as your skin adjusts.

What pairs well — and what to be careful with

Vitamin C pairs well with daily sunscreen and with hydrating ingredients like hyaluronic acid. If you also use strong exfoliating acids or retinoids, keep those to your evening routine — vitamin C in the morning, those actives at night — until you know how your skin responds. When in doubt, simpler is better.

Quick answers

How long does a bottle last? At 5–6 drops a day, a 1 fl oz bottle lasts most people about two to three months. For peak potency, finish an opened bottle within about three months.

Can I use it with SPF? Yes — apply vitamin C first, then sunscreen on top. That's exactly how it's meant to be used.

Why did my serum change color? Slight warming of color is normal; dark amber means it has oxidized and should be replaced.

Ready to start?

Every NuFountain serum is compounded in a small batch and hand-dated so you can see it. Shop the serums, or read the research behind L-ascorbic acid.