An overnight bio-collagen treatment mask developed by Yunji. Unlike a conventional sheet mask, where a cotton or cellulose carrier is simply soaked in essence, the sheet here is itself formed from collagen. It arrives as a dense, opaque gel film and gradually turns translucent over the course of wear as its contents transfer into the skin — the change in the sheet is the visible signal that the treatment is working.

The formula is built around three actives declared at concentration: a probiotic ferment filtrate and low molecular weight hyaluronic acid, both at 50,000 ppm (5%), together with low molecular weight collagen at 10,000 ppm (1%). Declaring active percentages on the front of the pack is unusual outside professional skincare, and it is the point of this product: the concentrations are high enough to do meaningful work in a single session rather than to justify a claim on a box.

The molecular weight matters more than the ingredient names. Standard collagen and standard hyaluronic acid are large molecules that sit on the surface of the skin and do very little beyond forming a temporary film. Hydrolysed into shorter chains, both fractions are small enough to settle into the upper layers of the stratum corneum, where they bind water for considerably longer. This is why a long wear time is central to how the mask is designed to be used.

Key ingredients

• Probiotic ferment filtrate — 50,000 ppm (5%) — a fermented filtrate rich in amino acids, vitamins, minerals and organic acids. It supports the skin's own microbial balance, and is associated in Korean formulation with improved radiance, a more refined surface texture and a reduction in the dull, uneven look of tired skin.
• Low molecular weight hyaluronic acid — 50,000 ppm (5%) — fragmented into short chains that reach past the outermost surface rather than resting on top of it. Each molecule binds many times its own weight in water, giving hydration that holds through the night instead of evaporating within the hour.
• Low molecular weight collagen — 10,000 ppm (1%) — hydrolysed collagen peptides that sit within the upper layers and form a moisture-retaining lattice. The immediate effect is a visible plumping of fine dehydration lines; the cumulative effect with regular use is skin that feels denser and more resilient.

How to use

1. Cleanse thoroughly and pat the skin dry. Apply toner if it forms part of your routine, and let it absorb.
2. Remove the mask from the sachet and unfold it. Position it over the face, aligning the eye and mouth openings, then smooth it outward from the centre to remove any air pockets.
3. Leave in place for a minimum of two hours. For the full effect, wear overnight — the mask adheres closely enough to stay in position while you sleep.
4. The sheet will turn from opaque to translucent as it is absorbed. Peel it away from the edge and discard.
5. Massage any remaining essence into the face, neck and décolleté until fully absorbed. Do not rinse. Follow with moisturiser only if your skin still feels tight.

Recommended frequency

• Normal to combination skin — once per week as maintenance.
• Dry or dehydrated skin — twice per week; three times weekly during winter or after air travel.
• Mature skin working on firmness — two to three times per week for a four-week course, then reduce to weekly.
• Before an occasion — use the night before rather than the morning of, which allows any redness from the adhesive contact to settle.
• What to expect — hydration and plumping are visible the following morning. Improvements in firmness and texture build over three to four weeks of consistent use.

Best suited to

Skin that is dehydrated, dull, or beginning to lose density and bounce. It suits all skin types, including sensitive skin, as the formula is centred on hydration and barrier support rather than on exfoliating acids or retinoids. It works particularly well as a recovery step after sun exposure, a long flight, a course of active ingredients, or a professional treatment — and it pairs comfortably with a retinol or acid routine, provided the mask is used on a night when those actives are not applied.

Specifications

• Format — bio-collagen overnight treatment mask, single use
• Volume — 34 g / 1.18 fl oz per sheet
• Available as — single sheet, or a four-pack at a reduced price
• Declared actives — probiotic ferment filtrate 50,000 ppm; low molecular hyaluronic acid 50,000 ppm; low molecular collagen 10,000 ppm
• Targets — hydration, revitalisation, firmness
• Texture — dense gel film, becoming translucent during wear
• Finish — no rinse required
• Minimum wear time — two hours; overnight recommended
• Origin — Korea

Good to know

Each sheet is intended for a single use and should not be re-applied. Store sealed, away from direct sunlight and heat. If you have reactive skin or a history of contact sensitivity, apply a small section along the jawline first and wait 24 hours before full use. The mask is a treatment rather than a replacement for daily moisturiser — continue your usual routine on the nights in between. Discontinue use if persistent irritation occurs.