How to Make a Facial Serum Formula for Beginners: Ingredients, Percentages & Testing
What Is a Facial Serum Formula?
A facial serum formula is a concentrated skincare product designed to deliver specific ingredients in a lightweight format.
Serums can vary widely depending on the type of product being created. Some are water-based, some are oil-based, and others use more complex systems.
Common serum goals include:
- Hydration
- Smoother-looking skin
- Brighter-looking skin
- Lightweight moisture
- Antioxidant support
- Improving the feel of dry or dull skin
The formula should be built around the type of serum you want to create, not around randomly combining popular ingredients.
What Ingredients Are Used in Facial Serums?
The ingredients depend heavily on whether the serum is oil-based or water-based.
Oil-Based Serum Ingredients
Oil serums may include ingredients such as:
- Jojoba oil
- Squalane
- Rosehip oil
- Grapeseed oil
- Meadowfoam seed oil
- Argan oil
- Sunflower oil
These ingredients can affect how lightweight, rich, silky, or greasy the serum feels.
Water-Based Serum Ingredients
Water-based serums may include ingredients such as:
- Distilled water
- Hydrosols
- Humectants
- Water-soluble botanical ingredients
- Cosmetic actives
- Thickeners
- Preservative systems
These formulas are generally more complex because preservation, pH, compatibility, and stability become important considerations.
Should Beginners Start With an Oil Serum or Water-Based Serum?
An oil-based serum can be structurally simpler for beginners because it does not require the same type of water-phase preservation system as a water-based serum.
That can make it easier to practice:
- Ingredient selection
- Percentages
- Texture
- Skin feel
- Formula tracking
- Batch scaling
Water-based serums can involve more variables and usually require more careful consideration of preservation, pH, ingredient compatibility, and stability.
Why Should Serum Formulas Be Written in Percentages?
Percentages make formulas easier to adjust, compare, scale, and reproduce.
Each ingredient is assigned a percentage, and the complete formula should total 100%.
For example:
- Ingredient A: 60%
- Ingredient B: 25%
- Ingredient C: 10%
- Additional ingredients: 5%
Total: 100%
This is simply an example of how a formula can be organized.
How Do You Calculate Serum Ingredient Weights?
Use:
Ingredient percentage ÷ 100 × total batch size = ingredient weight
For example, if one ingredient makes up 10% of a 100-gram formula:
10 ÷ 100 × 100 = 10 grams
For a 250-gram batch:
10 ÷ 100 × 250 = 25 grams
This makes it easier to create small test batches and scale later.
How Do You Choose Ingredients for a Facial Serum?
Start with the goal of the product.
Ask yourself what you want the serum to feel like and what type of product experience you want to create.
For example:
- Lightweight and fast absorbing
- Rich and emollient
- Silky
- Hydrating
- Minimal
- Designed for nighttime use
- Designed to layer underneath moisturizer
Once the goal is clear, ingredient selection becomes easier.
How Do You Avoid Making a Facial Serum Too Greasy?
An oil serum may feel too greasy if the blend contains too many heavy oils or if the overall formula leaves a strong oily film.
You may experiment with:
- Lighter-feeling oils
- Faster-spreading oils
- Reducing heavier oils
- Adjusting the ratio of the oil blend
Make one controlled adjustment at a time so you can identify what improved the texture.
Why Does My Serum Feel Sticky?
Stickiness is more common in some water-based serum formulas.
It may be affected by:
- High levels of certain humectants
- Thickening ingredients
- Ingredient combinations
- Overall formula structure
If your serum feels too sticky, changing several ingredients at once can make troubleshooting difficult.
Adjust one variable, document it, and compare the new version.
Why Is My Serum Too Thick?
A serum can become too thick if too much thickener is used or if multiple ingredients contribute to viscosity.
The result may feel more like a gel or cream than a serum.
When troubleshooting, review:
- Thickener percentage
- Ingredient interactions
- Hydration method
- pH requirements
- Processing method
Small percentage changes can sometimes have a large effect on viscosity.
Why Is My Serum Too Thin?
A serum may be too thin if the formula does not contain enough structure.
Depending on the formula, this may involve adjusting:
- Thickener
- Gelling agent
- Humectant balance
- Other viscosity-building ingredients
Always follow supplier instructions because different ingredients behave differently.
Does Facial Serum Need a Preservative?
It depends on the formula.
A traditional oil-based serum containing no water has different preservation concerns than a water-based serum.
Water-based formulas generally require an appropriate preservation strategy.
That includes products containing ingredients such as:
- Water
- Hydrosols
- Aloe juice
- Water-based botanical ingredients
Vitamin E is not a replacement for a broad-spectrum preservative.
If you plan to sell skincare products, preservation, stability, safety, and regulatory considerations should be taken seriously.
Why Is pH Important in Water-Based Serums?
pH can affect:
- Ingredient stability
- Preservative performance
- Skin compatibility
- Product texture
- Certain cosmetic actives
Some ingredients perform best within specific pH ranges.
Supplier documentation should be reviewed carefully when working with pH-sensitive ingredients.
If you are new to formulation, do not assume that mixing ingredients together automatically creates a stable finished product.
Can You Add Active Ingredients to a Facial Serum?
Yes, but active ingredients should be used carefully.
Each ingredient may have:
- Recommended usage levels
- Solubility requirements
- pH requirements
- Temperature limitations
- Compatibility considerations
Do not choose an active ingredient based only on a social-media trend.
Start with supplier documentation and understand how that ingredient fits into the formula.
Can You Mix Multiple Actives in One Serum?
You can sometimes combine multiple ingredients, but more is not automatically better.
Adding many actives can make a formula harder to troubleshoot.
If the finished product changes texture, separates, becomes unstable, or causes another formulation issue, it may be difficult to determine which ingredient caused the problem.
A simpler formula can be easier to test and improve.
Why Does a Facial Serum Separate?
Separation can happen for several reasons depending on the formula.
Possible causes include:
- Oil and water components not being properly incorporated
- Ingredient incompatibility
- Incorrect processing
- Insufficient solubilization or emulsification
- Temperature changes
- Formula instability
A separated serum should not automatically be fixed by simply shaking it and assuming the formula is successful.
The cause should be investigated.
How Do You Test a Facial Serum Formula?
Treat the first formula as Version 1.
Record:
- Ingredient names
- Percentages
- Supplier information
- Batch size
- Date made
- Texture
- Appearance
- Scent
- Absorption
- Skin feel
- pH when relevant
- Packaging performance
- Changes over time
Then review the product again after several days and weeks.
How Do You Improve a Serum Formula?
Identify the specific problem first.
For example:
Problem: The serum feels too sticky.
Rather than changing three or four ingredients, make one controlled adjustment.
Create Version 2 and compare it to Version 1.
That allows you to learn how individual changes affect the finished formula.
Why Should You Track Serum Formula Versions?
Once you begin testing formulas, organization becomes extremely important.
You may create:
- Serum V1
- Serum V2
- Serum V3
- Serum V4
Each version may contain only a small change.
Record:
- Exact percentages
- Ingredient weights
- What changed
- Texture observations
- pH observations
- Packaging notes
- Stability observations
- What you want to test next
Without good records, it can be difficult to recreate the version you liked.
Can You Scale a Facial Serum Formula?
Yes.
Once your formula is written in percentages and totals 100%, you can calculate ingredient weights for different batch sizes.
This makes it easier to begin with a small test batch before creating larger quantities.
Is Facial Serum a Good Product for Beginner Formulators?
It depends on the type of serum.
A simple oil-based serum can be a more approachable starting point.
A water-based serum may require a stronger understanding of:
- Preservation
- pH
- Ingredient compatibility
- Solubility
- Stability
- Manufacturing process
There is nothing wrong with beginning with simpler formulas while learning these concepts.
What Should You Learn Before Creating More Advanced Skincare?
If you are completely new to cosmetic formulation, start with our Beauty Product Formulation for Beginners guide.
If you want to practice with a simpler oil-based product first, read our How to Make a Body Oil Formula for Beginners guide.
Understanding percentages is also essential before moving into more complex formulas.
Want an Easier Way to Build and Organize Your Beauty Formulas?
As you move from simple oils into serums and more advanced skincare formulas, keeping everything organized becomes even more important.
Formula Lab™ Beauty Product Studio gives you one place to build formulas, work with percentages, organize product ideas, and keep track of what you are creating.