How to Formulate a Moisturizer: From Emulsion Type to a Cream That Holds

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Step 1: Decide What Your Moisturizer Is Actually Doing

Before you touch a single ingredient, get specific about the skin experience you're building toward. A moisturizer can do several things: reinforce the skin barrier, draw water into the upper layers, soften and smooth surface texture, or create a protective film that slows moisture loss. Most formulas do more than one of these, but the primary job shapes every decision that follows.

Ask yourself:

• Is this a day cream (lighter, sits under SPF or makeup) or a night cream (richer, more occlusive)?
• What skin type is it for? Dry skin tolerates more occlusives and emollients. Oily or acne-prone skin needs a lighter, faster-absorbing texture.
• Is there a hero active, like a peptide, niacinamide, or a botanical extract, that the formula needs to carry?

Write one sentence that completes this: "This cream helps the person using it feel _____ within _____ minutes of applying it, and their skin looks _____ by morning." That sentence is your formulation brief.

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Step 2: Choose Your Emulsion Type

A moisturizer is almost always an emulsion: oil and water mixed together and held stable by an emulsifier. The ratio and structure of that emulsion determines texture, skin feel, and how the product performs.

Oil-in-Water (O/W)

This is the most common structure for face creams and lotions. Water is the continuous phase; oil droplets are dispersed through it. The result is lighter, less greasy, and easier to spread. Most day creams, gel-creams, and lightweight moisturizers are oil-in-water.

Water-in-Oil (W/O)

Here oil is the continuous phase. The texture is richer and more occlusive. W/O emulsions tend to feel heavier and are better suited to barrier-repair products, cold-weather formulas, or very dry skin. They're also more challenging to stabilize and can feel greasy if the oil phase is too heavy.

Other Structures

Bicontinuous and multiple emulsions (W/O/W or O/W/O) exist and are used in prestige skincare, but they require specialized emulsifiers and more exacting process control. For a first formula, an oil-in-water cream formulation is the right starting point for most founders.

Pro tip: If you want a gel-cream texture, you're still working with an O/W base, but you're using a lower oil phase percentage and leaning on a gelling agent in the water phase to build body. The emulsion type doesn't change; the rheology does.

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Step 3: Build Your Water Phase

In a standard O/W moisturizer, the water phase typically makes up 60 to 80 percent of the formula. What you put in that phase, and in what amounts, sets the hydration story.

Water

Always use purified or deionized water. Tap water introduces minerals and microbial risk. The percentage of water in your formula is usually what's left after every other ingredient is accounted for, which is why it's listed as "q.s." (quantity sufficient) in a working formula.

Humectants

Humectants draw moisture into the skin. They live in the water phase. Common choices:

• Glycerin: Typically 2 to 10 percent. Lower percentages feel lighter; higher percentages can feel tacky on skin in dry climates. The grade (cosmetic vs. pharmaceutical) and the rest of your formula affect where in that range you land.
• Hyaluronic acid (sodium hyaluronate): Typically 0.1 to 2 percent. The molecular weight you choose changes the feel and the depth of hydration. High molecular weight sits on the surface; low molecular weight absorbs more readily.
• Niacinamide: Often used at 2 to 10 percent. It functions as more than a humectant (it supports the look of even skin tone and texture), but it lives in the water phase. At higher percentages, some suppliers note a flushing sensation on sensitive skin, so the grade and your target percentage matter.
• Panthenol (Provitamin B5): Typically 0.5 to 2 percent. Adds slip and supports a smooth skin feel.

Pro tip: Layering two or three humectants at moderate levels usually performs better than pushing one humectant to its ceiling. The combination addresses different mechanisms and keeps the texture clean.

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Step 4: Build Your Oil Phase

The oil phase in a face cream formulation typically runs 5 to 30 percent of the total formula, depending on the texture target. It contains your emulsifier, your emollient oils, and your occlusive ingredients.

Emulsifiers

The emulsifier is the ingredient that holds oil and water together. Choosing the wrong one, or using it outside its effective range, is the most common reason a cream separates. Typical usage levels run from 2 to 8 percent, but the right number depends on the specific emulsifier system and the oil load in your formula.

Some emulsifiers are single-ingredient systems (like certain cetearyl alcohol and ceteareth blends). Others work as pairs: a primary emulsifier and a co-emulsifier that boosts stability. Your emulsifier supplier's technical data sheet is the starting point for what percentage to use, and a chemist review confirms whether your specific formula is balanced.

Emollient Oils and Butters

These are what make the cream feel good on skin. They soften and smooth the surface, and different oils have different skin feels:

• Lighter, fast-absorbing oils (squalane, caprylic/capric triglycerides, jojoba): Good for day creams and oily-to-normal skin.
• Richer, slower-absorbing oils (shea butter, mango butter, rosehip oil): Better for night creams and dry skin.

Total emollient level in the oil phase typically runs 3 to 20 percent of the finished formula. The exact level depends on your texture target and your emulsifier's capacity to hold it.

Occlusives

Occlusives form a film on skin that slows water loss. Petrolatum is the most effective, but plant-derived waxes (like candelilla or carnauba) and certain silicones serve a similar function at lower percentages. If your formula is a lightweight day cream, you may use very little occlusive. A rich barrier cream might use more.

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Step 5: Add Your Actives

Actives are the ingredients that do the specific work your brief calls out: peptides, retinol, vitamin C derivatives, ceramides, plant extracts. Where they go in the formula depends on their solubility and stability.

• Water-soluble actives (most peptides, niacinamide, vitamin C derivatives like ascorbyl glucoside) go into the water phase.
• Oil-soluble actives (retinol, certain antioxidants like tocopherol, fat-soluble botanical extracts) go into the oil phase.
• Heat-sensitive actives are added after the emulsion has cooled, typically below 40°C. Probiotics, certain peptides, and fragrance fall into this category.

Where founders go wrong: Adding a heat-sensitive active to a hot emulsion. You'll know it happened when the active degrades and the product loses its intended effect, or when a fragrance note goes off. The fix is a strict cool-down protocol before you add anything sensitive.

Pro tip: Some actives affect emulsion stability. High concentrations of certain vitamin C forms can drop the pH of your formula and destabilize your emulsifier. Always check the active's technical data sheet for compatible pH range and known incompatibilities.

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Step 6: Preserve It

A moisturizer without adequate preservation is a contamination risk. Water-containing formulas support microbial growth, and a contaminated product can cause serious skin reactions for the person using it.

Preservative systems vary widely. Broad-spectrum options like phenoxyethanol, ethylhexylglycerin, or approved paraben blends are common. Natural preservation systems (using ingredients like levulinic acid, rosemary extract, or high-antioxidant oils) can work but require challenge testing to confirm efficacy.

Typical usage levels for most preservative systems run from 0.5 to 1.5 percent, but the effective level depends on the preservative, your formula's pH, and the water activity in your product. Legal limits apply in both the US (FDA) and the EU (EC Cosmetics Regulation), and those limits are checked when a chemist reviews the formula.

Where founders go wrong: Assuming a preservative is "natural" means it needs less rigorous testing. Preservation efficacy is confirmed by challenge testing (also called microbial challenge or preservative efficacy testing), not by ingredient reputation.

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Step 7: Adjust pH

Most face cream formulas perform best in the range of 4.5 to 6.5, which is close to the skin's natural pH. Some actives have narrower requirements: vitamin C derivatives are often most stable at 3.5 to 4.5, while certain peptides prefer a higher pH.

You adjust pH with a buffer system, typically citric acid to bring it down or sodium hydroxide (in dilute solution) to bring it up. Small adjustments. Add slowly, mix thoroughly, and recheck.

Pro tip: pH also affects your preservative's efficacy. Phenoxyethanol, for example, works best below pH 6. If your formula needs a higher pH for an active, you may need a different preservative system or a dual approach.

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Step 8: Add Fragrance or Masking Agents

Fragrance goes in last, after the emulsion has cooled, at 0.1 to 1 percent for most face products. If your formula is fragrance-free (a smart positioning choice for sensitive-skin products), a small amount of a masking agent can neutralize the raw smell of certain base ingredients without adding a detectable scent.

If you're using a fragrance blend, your supplier should provide an IFRA compliance statement confirming the blend is safe at your intended use level for a leave-on face product.

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Step 9: Check for Stability

A formula that looks perfect on day one can separate, discolor, or grow mold by month three. Stability testing catches these problems before they become a customer problem.

The standard approach:

• Accelerated stability: Store samples at elevated temperature (typically 40°C) and check at 4, 8, and 12 weeks for separation, color change, odor change, and pH drift.
• Freeze-thaw cycling: Three cycles of freezing and thawing to simulate shipping and storage stress.
• Real-time stability: Samples stored at room temperature for the shelf life you intend to claim.

Signs a cream has failed stability: Oil pooling on the surface or around the edges of the jar. A grainy or gritty texture that wasn't there before. A pH reading that has shifted more than 0.5 units. An off smell. Any of these is a signal to revisit the emulsifier system, the preservative, or the active compatibility.

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Moisturizer Formula Percentages: A Reference Framework

These are typical ranges for a standard O/W face cream. Every number moves based on the specific ingredients you choose, your supplier's guidance, and the rest of the formula.

These ranges are starting points. A chemist review is what confirms whether your specific combination is stable, safe, and manufacturable.

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How Genie Fits Into This Process

Building this formula by hand, sourcing every ingredient, and working through compatibility by trial and error takes months. Genie is the AI formulator for indie brands, and it compresses that process significantly.

You describe the product you want to build. Genie generates a full custom formula, with exact ingredient percentages and ingredient costs, drawn from a 180,000-row ingredient database with chemistry data behind every selection. The full formula is yours for free, including every percentage and every cost line. Nothing about the formula is gated.

When you're ready to make the product, you start production with a $500 refundable deposit. An experienced chemist reviews your formula and prepares the final spec documents your manufacturer works from, back within five business days. Genie then matches you with a contract manufacturer and gets you their sample pricing before you pay it. You try real samples before you approve any run. Your deposit is refunded in full any time before you approve your run, or if Genie cannot make your product.

Genie develops the formula. Contract manufacturers produce it. That boundary matters: Genie is not a manufacturer, and the manufacturing price is your manufacturer's own, with nothing added to it.

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Frequently Asked Questions

What is the typical water percentage in a face cream formula?

In a standard oil-in-water face cream, water typically makes up 50 to 75 percent of the formula. The exact percentage depends on your texture target: a lightweight gel-cream sits toward the higher end, while a rich night cream might use less water and more emollient and occlusive ingredients. Water is usually listed as "q.s." (quantity sufficient) because it fills whatever percentage remains after all other ingredients are accounted for.

How do I know if my moisturizer formula is stable?

The most reliable method is accelerated stability testing: storing samples at elevated temperature (around 40°C) and checking at regular intervals for separation, color change, odor change, and pH drift. Signs of failure include oil pooling on the surface, a gritty texture, a pH shift of more than 0.5 units from the original, or an off smell. Freeze-thaw cycling and real-time storage testing at room temperature round out a complete stability protocol.

What percentage of emulsifier do I need in a face cream?

Most emulsifier systems are used at 2 to 8 percent of the total formula, but the right level depends on the specific emulsifier, the oil load in your formula, and whether you're using a single emulsifier or a paired system. Your emulsifier supplier's technical data sheet gives you a starting range, and a chemist review confirms whether your specific formula is balanced. Using too little emulsifier is the most common reason a cream separates.

Can I add vitamin C to a moisturizer formula?

Yes, but the form of vitamin C matters. Pure ascorbic acid is highly effective but unstable in water-based formulas and requires a low pH (around 3.5) to stay active, which can conflict with other ingredients and irritate sensitive skin. Stabilized derivatives like ascorbyl glucoside or sodium ascorbyl phosphate are more formula-friendly and work at a less acidic pH. Always check the active's compatible pH range and known incompatibilities before finalizing your formula.

Do I need a preservative in a moisturizer?

Yes. Any formula that contains water supports microbial growth, and a contaminated product poses a real risk to the person using it. Preservative systems vary, and both the US (FDA) and the EU (EC Cosmetics Regulation) set limits on specific preservatives. Challenge testing (also called preservative efficacy testing) is the only way to confirm your system actually works in your specific formula. A chemist review checks that your preservative is both effective and compliant.

What is the difference between an emollient and an occlusive?

Emollients soften and smooth the skin's surface by filling in gaps between skin cells. They make the product feel good to apply and improve skin texture. Occlusives form a physical film on the skin that slows water loss. Many ingredients do both to some degree, but the distinction matters when you're building a formula: a day cream might lean heavily on emollients for a smooth, non-greasy feel, while a barrier-repair cream might use more occlusives to lock in moisture over time.

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Key Takeaways

• Start with a clear brief: what the product does for the person using it, and what skin experience you're building toward.
• Oil-in-water is the right starting structure for most face creams. The emulsifier choice and oil load determine stability.
• Build your water phase with layered humectants. Build your oil phase with the right emulsifier-to-oil ratio.
• Add heat-sensitive actives after the emulsion cools. Check every active for pH compatibility and emulsion impact.
• Preservation is not optional. Challenge testing confirms your system works.
• Typical moisturizer formula percentages are ranges, not fixed numbers. What moves them is the specific ingredient, the grade, and the rest of the formula.
• Stability testing is the only way to know your formula will hold.

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