Numbuzin may not yet be a household name in every beauty cabinet, but within K-beauty circles its smartly numbered lineup has been gathering quiet applause for formulas that punch above their price tags. The brand likes to let the products speak for themselves and, more often than not, they do.
Enter the rather memorably titled No.6 Deep Sleep Mask Serum. The name sounds like something concocted in a dream lab, and the official promise is even dreamier: an overnight veil powered by glacier water that drenches tired skin so you wake up looking fresh from an eight-hour spa session. A couple of pumps at bedtime is said to deliver pillow-proof hydration without smothering pores while smoothing lines in the bargain.
To see if that bedtime story holds up, I swapped out my usual night treatment and committed to two straight weeks with No.6. Night after night it was the last thing on my face before lights out, giving me a fair shot at judging the glow, the slip and everything in between.
Disclosure: this review is not sponsored or paid. The serum was purchased with personal funds and every opinion here is based on my own experience. As always with skincare, your mileage may vary.
What Is No.6 Deep Sleep Mask Serum?
This product is an overnight treatment, meaning it is designed to work while you sleep rather than being rinsed off after a few minutes. Overnight treatments create a breathable layer on the skin so active ingredients can stay put and do their job until morning.
Numbuzin positions No.6 as a hybrid between a lightweight serum and a sleeping mask. The formula centers on glacier water and multiple humectants, backed by niacinamide and plant extracts. After cleansing and toner, two or three pumps are smoothed over the face as the final step. It absorbs quickly to avoid pillow transfer yet aims to keep skin hydrated through the night.
By combining hydration support with mild brightening and a soft occlusive effect, the mask serum is meant to cut down on the need for separate creams or oils at bedtime. The goal is simple morning skin that feels less tight and looks a touch more rested.
Did It Work?
In the name of very scientific research I benched my longtime overnight cream for three full days before starting this test drive, giving my skin a blank slate and a little drama break. Fourteen nights felt like a fair window to judge whether the dreamy glacier water would live up to its marketing poetry.
Application was pleasantly brain-off: two pumps after toner, quick press in, lights out. The texture sits somewhere between essence and light gel, sliding on with a cool slip then settling into a barely tacky film that disappeared after ten minutes. Night one I woke up to a subtle plushness around the cheeks but nothing that had me texting friends. By night three dehydration lines at the corners of my mouth looked less etched, a small win during office-heater season.
The middle stretch, nights four through ten, delivered the peak performance. My skin held moisture through the night so I stopped needing a mist by lunch. Makeup went on a touch smoother and the usual morning dullness dialed down a notch. I did not notice any real brightening of post-blemish marks despite the niacinamide on the roster, and one tiny whitehead appeared on my chin around day eight though it cleared quickly.
From day eleven onward the benefits seemed to plateau. Hydration remained steady yet never climbed into wow territory and I started to miss the cushier finish of a heavier sleeping mask. The serum never clogged pores but it also never delivered the line-smoothing fairy tale implied on the box. I finished the fortnight with skin that felt balanced and calm, just not transformed.
So did it work? Partly. No.6 kept my complexion comfortably hydrated and non-greasy which checks the main claim, but the promised morning-after radiance stayed in the polite-glow zone. I will finish the bottle on warm nights or travel when I crave a breathable layer, yet I am not rushing to give it a permanent spot in my personal lineup.
No.6 Deep Sleep Mask Serum’s Main Ingredients Explained
The ingredient list reads like a hydration hit parade, starting with glacier water as the first item on deck. While “glacier” is mostly marketing sparkle for ultra purified H2O, the real workhorses are classic humectants: butylene glycol, propanediol and glycerin pull moisture from the air into the skin’s upper layers. They are joined by a trio of hyaluronic acids in different molecular sizes, including cross-linked sodium hyaluronate, which stick around longer before evaporating and give that plumped cheek look after a few nights.
Niacinamide shows up early on the list at a concentration likely between 4 and 5 percent. This vitamin B3 derivative is beloved for brightening dark spots, reinforcing the skin barrier and calming redness. Alongside it sits panthenol, another B vitamin that converts to provitamin B5 in the skin to soothe and reduce water loss. Adenosine rounds out the functional actives, pitching in a mild line-softening effect by encouraging surface cell energy production.
The formula leans into a garden of plant extracts such as neem leaf, eggplant fruit and turmeric root, which contribute antioxidants and a bit of anti inflammatory support. Chlorella and red algae add extra minerals while remaining light in texture. Importantly, there are no heavy oils, shea or waxes that often trip the clogging alarm for acne-prone users. On the widely referenced comedogenic scale, most components here rate a 0 or 1 meaning they are unlikely to block pores though individual reactions can vary. (Comedogenic simply refers to an ingredient’s tendency to create comedones, better known as blackheads or whiteheads.)
Good news for plant-based shoppers: every item on the INCI roster is synthetically derived or botanical so the serum is suitable for vegans and vegetarians. I also spotted no added fragrance or drying alcohol which should please sensitive skin, but the multitude of botanicals could still pose an irritation risk for the very reactive crowd.
Expectant or nursing users should remember that even friendly ingredients like niacinamide and adenosine have limited safety data during pregnancy. The safest route is to run the formula by a healthcare professional before slathering anything new on hormonally shifting skin.
One final callout: the pH sits around 5.5 giving a skin-friendly slightly acidic environment that helps maintain the moisture barrier while discouraging bacterial overgrowth. In short, the cocktail is thoughtfully balanced for nightly use though not quite groundbreaking in potency, aligning neatly with its middle-of-the-road price and that solid 7 out of 10 performance.
What I Liked/Didn’t Like
After a fortnight of nightly use here is the straightforward rundown.
What Works Well:
- Lightweight, serum-gel texture sinks in quickly so there is no sticky pillow situation
- Reliable overnight hydration that keeps dryness at bay and gives morning skin a refreshed feel
- Ingredient lineup is fragrance free, vegan friendly and largely non-comedogenic which broadens the potential user base
What to Consider:
- Results plateau after about ten nights so long-term wow factor may be limited
- Brightening claims are modest; post-blemish marks looked unchanged
- Those who prefer a richer occlusive layer might still need a cream on top which reduces the one-step appeal
My Final Thoughts
Two weeks in the sack with No.6 Deep Sleep Mask Serum left me quietly appreciative yet not utterly smitten. It is the kind of overnight treatment I would call a dependable roommate rather than a soulmate: always there with a glass of water, never the spark that makes you pen poetry. Hydration was solid, my skin stayed calm and makeup sat better in the morning, but the vaunted spa-morning luminosity only ever hovered at polite candlelight level. I have logged skin hours with more decadent sleeping masks and feather-light gel serums alike, so I feel I gave this one a fair shake before landing on a 7/10 rating. Would I recommend it? To the combination-to-oily crowd hunting for fuss-free nightly moisture, absolutely. For dry or mature skins chasing plush cushiony bounce, I would gently steer you toward something richer or suggest layering a cream on top, which admittedly defeats the one-step fantasy.
If you fall into the latter camp or simply want options, I have a little black book of overnight stand-ins. Deascal’s Nocturnal Revive Cream is my current all-rounder crush: straightforward formula, friendly price tag and a texture that somehow manages to please both my T-zone and my drier cheeks. Medik8’s Advanced Night Restore offers a subtly cocooning feel laced with ceramides that makes winter radiators less evil. Laneige Water Sleeping Mask remains an old faithful whenever I want weightless hydration that still delivers plumpness by dawn. Finally, IT Cosmetics Confidence in Your Beauty Sleep tips the scale toward comfort food for the face, smoothing rough patches without leaving a greasy film. I have rotated through each of these jars and tubes enough nights to vouch for their reliability and quirks.
Back to our star of the show: No.6 is for the minimalist who wants to ditch heavy night creams when the weather warms or the breakout fairy looms. It is not for anyone hoping to blur fine lines in a fortnight or erase stubborn post-blemish shadows. I will keep my bottle for travel and sticky summer nights but I will not be drafting an ode to it anytime soon.
Before you slather anything new on, a quick PSA from your over-protective skincare buddy: patch test on the jaw or inner arm for a couple of nights first, especially if your skin throws tantrums easily. Remember that glowing results stick around only as long as you keep up the routine so pace yourself and stay consistent.