Once you are comfortable weighing ingredients, working in percentages and making simple oil serums, THDC becomes much more interesting.

Formulate With Confidence — Download the Free Guide

Because Tetrahexyldecyl Ascorbate (THDC) is oil soluble, it can be incorporated into far more than conventional Vitamin C facial oils.

In this intermediate guide we will make:

1. Crystal Vitamin C Oil Jelly

2. Shake-to-Glow Bi-Phase Serum

3. Barrier Cloud Cream

4. Airless Vitamin C Gel-Cream

5. Overnight Antioxidant Sleeping Glaze

6. Illuminating Vitamin C Body Oil Gel

Each formula introduces a different formulation technique.

For simplicity, the formulas are shown as 100 g test batches.

That means:

1% = 1 g

So if a formula contains 5% THDC, a 100 g batch requires 5 g THDC.

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Before You Begin

Intermediate formulation introduces several things that were deliberately avoided in the beginner guide:

• heating;

• emulsification;

• pH adjustment;

• preservatives;

• polymer activation;

• solubilising powdered actives;

• suspension;

• cool-down phases;

• different oil and water phases.

A digital scale reading to 0.01 g, heat-resistant beakers, thermometer, pH meter, spatulas and suitable mixing equipment become much more important.

Whenever water is present, use an appropriate broad-spectrum cosmetic preservative at the manufacturer's recommended concentration.

Finished commercial cosmetics require appropriate stability, compatibility, microbiological and safety assessment.

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Formula 1 — Crystal Vitamin C Oil Jelly

Skill Level: ★★★☆☆

What You Learn

How to turn a liquid oil serum into a glossy transparent oil gel.

Rather than producing another ordinary facial oil, this formula creates a luxurious jelly-like Vitamin C treatment.

The key ingredient is Olikemia™ 5S CC Polymer, an oil-phase structuring polymer that can create transparent or translucent oil gels and suspend materials without the opacity associated with conventional waxes. JustGlow lists a typical use range of 0.5–6% and an activation temperature of approximately 80–100°C.

Formula — 100 g

Ingredient	%	Weight
THDC	8%	8 g
Olikemia™ 5S	4%	4 g
Hydra Synol® DOI	8%	8 g
Bakuchiol	1%	1 g
Pomegranate Seed Oil	10%	10 g
Squalane	25%	25 g
Hemisqualane	43%	43 g
Alpha-Bisabolol	0.5%	0.5 g
Tocopherol	0.5%	0.5 g
Total	100%	100 g

Hydra Synol DOI is an oil-soluble emollient and spreading agent that JustGlow recommends at around 1–20%, while Bakuchiol is an oil-soluble active typically used around 0.5–2%.

Method

Phase A — Polymer Activation

Combine:

• Olikemia™ 5S

• Squalane

• Hydra Synol DOI

Heat to approximately 90°C while mixing.

Hold long enough for the Olikemia polymer to become fully activated and uniform.

Olikemia can sometimes look dissolved before complete activation, so adequate heat and mixing are important.

Phase B — Cool Down

Begin cooling while mixing.

Below approximately 45°C add:

• Hemisqualane

• Pomegranate Seed Oil

Below approximately 40°C add:

• THDC

• Bakuchiol

• Bisabolol

• Tocopherol

Mix thoroughly.

Allow the formulation to stand before evaluating its final viscosity because the oil-gel structure develops as it cools.

Finished Product Concept

Crystal C Jelly Serum

Package in:

• premium airless jar;

• glass treatment pot;

• squeeze tube.

It should have the appearance of an expensive translucent treatment rather than an ordinary facial oil.

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Formula 2 — Shake-to-Glow Bi-Phase Vitamin C Serum

Skill Level: ★★★☆☆

What You Learn

How to deliberately formulate a product that separates into two beautiful phases.

Not every cosmetic needs to remain emulsified.

A bi-phase serum contains an aqueous layer and an oil layer and is deliberately shaken immediately before use.

This makes it possible to combine:

Water-soluble actives

• Ectoin

• Alpha Arbutin

with:

Oil-soluble actives

• THDC

• Pomegranate Oil

• Hydra Synol DOI

• Bisabolol

in one visually interesting product.

Ectoin is water soluble, while Alpha Arbutin should be incorporated into the aqueous phase below about 40°C and maintained around pH 4–6.5.

Formula — 100 g

Water Phase

Ingredient	%
Distilled Water	50%
Glycerin	4%
Dimethyl Isosorbide	5%
Ectoin	1%
Alpha Arbutin	2%
Phenoxyethanol/Ethylhexylglycerin	1%

Oil Phase

Ingredient	%
THDC	5%
Hydra Synol DOI	5%
Squalane	14%
Pomegranate Seed Oil	7%
Hemisqualane	5%
Bisabolol	0.5%
Tocopherol	0.5%
Total	100%

DMI is useful here because it is miscible with water, glycols and many cosmetic oils and can act as a formulation solvent and blending aid. JustGlow recommends approximately 1–10%.

Method

Phase A

Combine water, glycerin and DMI.

Dissolve Ectoin.

When the mixture is below 40°C, dissolve Alpha Arbutin.

Add preservative.

Phase B

Separately combine:

THDC + DOI + Squalane + Pomegranate Oil + Hemisqualane + Bisabolol + Tocopherol.

Mix until completely homogeneous.

Assemble

Pour the aqueous phase into a transparent serum bottle.

Slowly add the oil phase.

Allow the layers to separate naturally.

Check and adjust the aqueous phase pH to approximately 5–5.5 before filling.

Packaging

A clear bottle makes the separation part of the product experience.

Add:

SHAKE WELL BEFORE USE

to the label.

Why This Concept Is Interesting

Instead of trying to force chemically different ingredients into one homogeneous phase, the separation becomes part of the design.

It also photographs beautifully for product pages and social media.

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Formula 3 — THDC Barrier Cloud Cream

Skill Level: ★★★☆☆

What You Learn

Traditional hot-process emulsification and multi-active phase management.

This is a more sophisticated cream combining antioxidant, barrier and soothing ingredients.

The structure comes from PolyAquol™ 2W, a polyglycerol-based self-emulsifier used at approximately 1–5%. JustGlow recommends heating to around 65–70°C for incorporation and emulsifying at approximately 75°C when using a hot process.

Formula — 100 g

Phase A — Water

Ingredient	%
Distilled Water	64%
Glycerin	4%

Phase B — Oil

Ingredient	%
PolyAquol™ 2W	4%
THDC	5%
Hydra Synol DOI	5%
Pomegranate Seed Oil	5%
Squalane	5%
Ceramide Complex / Ceramide Oil	2%
Cholesterol	0.5%
DPHP	2%
Bakuchiol	0.5%
Bisabolol	0.5%
Tocopherol	0.5%

Phase C — Cool Down

Ingredient	%
Ectoin	1%
Broad-Spectrum Preservative	1%
Total	100%

Method

Heat water and glycerin to approximately 70–75°C.

Separately combine the structural oil-phase ingredients and PolyAquol.

Heat until fully uniform.

Add THDC toward the end of the heating stage rather than holding it unnecessarily at elevated temperature.

Combine phases and homogenise.

Continue mixing while cooling.

Below 40°C add:

• Ectoin;

• preservative;

• any particularly heat-sensitive supplier-specific components.

Check final pH and adjust if required by your preservative and other ingredients.

Finished Concept

Vitamin C Barrier Cloud Cream

This could be positioned as a soft, cushiony night cream rather than another conventional Vitamin C serum.

It also demonstrates how one formula can combine water-soluble and oil-soluble JustGlow ingredients.

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Formula 4 — Airless Vitamin C Gel-Cream

Skill Level: ★★★★☆

What You Learn

Polymer emulsification, neutralisation and pH control.

This formulation uses Pemulen™ EZ-4U rather than a traditional waxy emulsifier.

Pemulen EZ-4U is a water-dispersible polymeric emulsifier/rheology modifier typically used around 0.2–1%. It develops viscosity following neutralisation and can create light oil-in-water gel-creams.

Formula — 100 g

Ingredient	%
Distilled Water	q.s. to 100%
Glycerin	4%
Pemulen™ EZ-4U	0.4%
DMI	4%
Ectoin	1%
Alpha Arbutin	2%
THDC	5%
Hydra Synol DOI	4%
Squalane	3%
Bisabolol	0.5%
Tocopherol	0.5%
Broad-Spectrum Preservative	1%
10% TEA Solution	q.s. to pH

Why There Is No Exact Water Percentage

This formula introduces an important professional formulation concept:

q.s. = quantity sufficient

You do not know exactly how much TEA solution will be needed until you neutralise the polymer and measure the pH.

Therefore water makes up whatever quantity is required to bring the final batch to exactly 100%.

Method

Phase A

Add water to the main vessel.

Disperse Pemulen EZ-4U under moderate agitation.

Avoid unnecessarily aggressive shear before neutralisation.

Add glycerin and DMI.

Phase B

Combine:

• THDC

• Hydra Synol DOI

• Squalane

• Bisabolol

• Tocopherol

Emulsification

Slowly add Phase B into Phase A while mixing.

Begin neutralising gradually using the 10% TEA solution.

Watch the formulation transform from a thin dispersion into a gel-cream.

Cool Down

Below 40°C incorporate:

• Ectoin

• Alpha Arbutin

• Preservative

Adjust final pH to approximately 5.2–5.5, provided this is compatible with the preservative system selected.

Alpha Arbutin is most stable within approximately pH 4–6.5 and should avoid unnecessary high-temperature processing.

Product Concept

Vitamin C Water-Gel Moisturiser

Package it in an airless pump.

The finished format should feel closer to a serum than a conventional cream.

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Formula 5 — Overnight Antioxidant Sleeping Glaze

Skill Level: ★★★★☆

What You Learn

Powder solubilisation + polymer activation + multiple oil-soluble actives.

This is where the intermediate guide starts becoming genuinely interesting.

The formula combines:

• THDC;

• Acetyl Zingerone;

• Bakuchiol;

• DMI;

• Hydra Synol DOI;

• Bisabolol;

• Pomegranate Oil;

• Olikemia.

Acetyl Zingerone is an antioxidant ingredient used at low concentrations. JustGlow lists approximately 0.05–1%, with oil-phase incorporation or pre-solubilisation depending on the formulation.

Formula — 100 g

Ingredient	%
THDC	10%
Acetyl Zingerone	0.5%
DMI	5%
Hydra Synol DOI	10%
Bakuchiol	1%
Bisabolol	0.5%
Pomegranate Seed Oil	10%
Squalane	25%
Hemisqualane	34%
Olikemia™ 5S	3%
Tocopherol	1%
Total	100%

Method

Step 1 — Pre-Dissolve Acetyl Zingerone

Combine Acetyl Zingerone with the DMI.

Mix until dissolved.

DMI is specifically useful for difficult-to-incorporate powders and crystalline materials.

Set aside.

Step 2 — Activate Olikemia

Combine:

• Olikemia

• Squalane

• Hydra Synol DOI

Heat to approximately 90°C until completely activated.

Step 3 — Cool

Begin cooling.

Add Hemisqualane and Pomegranate Oil.

Below approximately 40°C add:

• pre-dissolved Acetyl Zingerone;

• THDC;

• Bakuchiol;

• Bisabolol;

• Tocopherol.

Mix thoroughly.

Finished Concept

Vitamin C Overnight Skin Glaze

Think somewhere between:

serum + oil + sleeping treatment

rather than another liquid dropper serum.

A soft translucent gel in a luxury jar would make this particularly distinctive.

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Formula 6 — Illuminating Vitamin C Body Oil Gel

Skill Level: ★★★☆☆

What You Learn

Suspending an insoluble decorative material inside an anhydrous oil system.

THDC does not have to be restricted to facial skincare.

Olikemia can also suspend pigments and cosmetic particles in structured oils, which makes it particularly interesting for illuminating body products.

Formula — 100 g

Ingredient	%
THDC	2%
Olikemia™ 5S	3%
Hydra Synol DOI	10%
Pomegranate Seed Oil	10%
Squalane	20%
Hemisqualane	53%
Bisabolol	0.5%
Tocopherol	0.5%
Cosmetic Mica	1%
Total	100%

Method

Combine Olikemia with the Squalane and Hydra Synol DOI.

Heat to approximately 90°C and mix until the polymer is fully activated.

Begin cooling.

Add Hemisqualane and Pomegranate Seed Oil.

Disperse cosmetic mica carefully and mix until evenly suspended.

Below approximately 40°C add:

• THDC;

• Bisabolol;

• Tocopherol.

Continue mixing as the formulation cools.

Finished Concept

Vitamin C Golden Body Veil

The aim is a:

• glossy;

• lightweight;

• shimmering;

• non-waxy;

• visually luxurious

body treatment.

Olikemia provides the structure needed to help keep decorative particles suspended rather than immediately settling to the bottom.

This would be particularly attractive in transparent packaging.

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What Each Formula Teaches You

Formula	Main Skill
Crystal Oil Jelly	Oil polymer activation
Shake-to-Glow Serum	Bi-phase formulation
Barrier Cloud Cream	Hot-process emulsification
Airless Gel-Cream	Polymer neutralisation & pH
Sleeping Glaze	Active solubilisation
Body Oil Gel	Particle suspension

This progression is deliberate.

A formulator who can confidently make all six has moved beyond simply following oil-serum recipes and has started learning how cosmetic structure itself is designed.

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The Intermediate Formulator's Notebook

At this stage, start recording more than the ingredients and weights.

For every batch note:

Before Making

• Formula number

• Batch number

• Ingredient supplier

• Ingredient lot/batch

• Target batch size

• Target pH

• Target appearance

• Target packaging

During Manufacture

• Actual ingredient weights

• Heating temperature

• Mixing time

• Order of addition

• pH adjustments

• Observations during emulsification

• Cooling temperature

After Manufacture

Record observations:

Day 0
24 Hours
1 Week
2 Weeks
4 Weeks

Look for:

• separation;

• crystallisation;

• colour changes;

• odour changes;

• viscosity change;

• sedimentation;

• oil bleeding;

• pH drift;

• packaging compatibility.

This habit is one of the biggest differences between simply making skincare and actually formulating it.

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A Note About Heat-Sensitive Actives

Not every ingredient needs to be added at the beginning of a heated process.

Ingredients such as Alpha Arbutin and Ectoin are better handled in cooler processing stages; JustGlow's current guidance recommends Alpha Arbutin below approximately 40°C and Ectoin in the cool-down phase.

By contrast, Olikemia requires substantial heat for polymer activation.

This is why intermediate formulation is largely about planning the order of addition.

You might need to heat one part of the formula to 90°C while deliberately keeping another ingredient below 40°C.

The formulation method is therefore just as important as the ingredient list.