The one that started it all: 20% L-ascorbic acid and little else — four ingredients, no fragrance and no fillers. If you want the most-studied form of vitamin C at full strength, this is the purist's serum. Why fresh matters 20% L-ascorbic acid is the most effective form of vitamin C — and also the fastest to break down once mixed. A pre-made bottle that has sat on a shelf for months has already lost some of its punch. We blend in small batches and hand-date every bottle so simplicity actually means potency. What it does Brightens & evens tone. Helps visibly reduce the look of dark spots, sun marks and dullness for a clearer, more radiant complexion over time. Supports collagen. Vitamin C is essential to your skin's own collagen production, helping keep skin looking firm and smooth. Daily antioxidant. Helps neutralize free radicals from sun and pollution that would otherwise speed visible aging. Key ingredients L-Ascorbic Acid — The pure, active form of vitamin C with the deepest research behind brightening, firmness and antioxidant protection. Glycerin — A gentle humectant that keeps the high-strength formula comfortable and non-drying. Full ingredients: Purified Water, 20% L-Ascorbic Acid, Magnesium Sulfate, Glycerin. How to use Cleanse skin. Apply 5–6 drops. Pat gently over the face and neck. A mild, warm tingle is normal at this strength. Let it absorb for a minute. Follow with moisturizer, and sunscreen every morning. New to vitamin C? Start every other day and build up. Patch test first if your skin is sensitive. Keep the cap tight and store in a cool, dark place — refrigerate unopened bottles. If the serum turns deep amber, it has oxidized and it's time for a fresh one. Vitamin C works best with daily sunscreen We don't sell sunscreen, but it's the one step that protects everything this serum works toward. Without daily SPF, UV light breaks vitamin C down, drives new dark spots and speeds collagen loss — so your serum is left fighting an uphill battle. With it, you lock in and protect your progress. What to look for in a sunscreen: Broad-spectrum — protects against both UVA (aging) and UVB (burning) rays. SPF 30 or higher — blocks about 97% of UVB; don't drop below 30. Every morning — apply as the last step after your serum, and reapply every two hours in the sun. A texture you'll actually wear — mineral (zinc oxide, titanium dioxide) or a modern chemical filter; pick one that feels good so you use it daily. FAQ Why only four ingredients?Because L-ascorbic acid is what does the work. We leave out fragrance, oils and fillers so you get a clean, high-strength dose of vitamin C and nothing your skin doesn't need. Should I choose C20 Original or C20 Ferulic?Choose Original if you want the simplest vitamin C. Choose Ferulic if you'd like added antioxidant support from ferulic acid plus more hydration from hyaluronic acid. Both use the same 20% L-ascorbic acid. Will 20% be too strong for me?Most skin adjusts well if you ease in — start every other day and build up. If you're sensitive or new to vitamin C, our C10 (10%) or tingle-free C15 MAP are gentler starting points. How should I store it, and how long does it last?Keep the cap closed and store in a cool, dark spot; refrigerate unopened bottles to extend freshness. Once opened, use it within about three months. A deep amber color is your signal it has oxidized and it's time for a fresh bottle. What if it doesn't work for me?You're covered by our 30-day money-back guarantee. Contact us within 30 days of delivery and we'll refund you in full — no need to return the bottle. Small-batch · Hand-dated · Shipped from Colorado · 30-day money-back guarantee · Free U.S. shipping over $50.
