Formulation
How should I approach formulation as a beginner?
Learn the protocol, then learn what each ingredient does and why it goes in at a particular phase and temperature, before you start changing recipes.
The Big Book of Homemade Skin Care
Formulation
A formula is a sequence of decisions.
What goes in, how much, at what temperature, and in what order. These are the principles behind every formula in the books, gathered in one place.
The structure of a cream
The book's creams follow a consistent architecture. Typical ranges:
| Part | Share | Includes |
|---|---|---|
| Water phase | 55–75% | Water or hydrosols, 3–5% glycols or glycerin, water-soluble extracts |
| Oil phase | 15–27% | Carrier oils, squalane, 3–5% emulsifier, 1.5–2.5% cetearyl alcohol, ~0.5% vitamin E |
| Actives | 2–8% | Added below 40 °C |
| Preservative | ~1% | Broad-spectrum, added at about 35 °C |
| pH adjuster | q.s. | 10% citric or lactic acid, drop by drop |
| Ingredient type | Range used in the books |
|---|---|
| Preservative | 0.5–2% |
| Essential oil in face products | ≤ 1% |
| Panthenol | 1–5% |
| Emulsifier | 3–5% |
| Cetearyl alcohol | 1.5–2.5% |
| Vitamin E | 0.3–3.3% |
| Polysorbate 80 in scrubs | 4–5% |
The emulsion timeline
From the Barrier Repair Cream method. Each temperature exists to protect something.
- 70–72 °CHeat oil and water phases separately; hold the water phase about 5 minutes
- 70–72 °CPour oil into water in a thin stream; mix on high 3–4 minutes
- 38–40 °CAdd actives one at a time while cooling
- 35 °CAdd the preservative; mix 1–2 minutes; check the pH
- 25–28 °CStop stirring, pack, and rest 24 hours
The sterilization chain
- Clean in hot soapy water.
- Rinse with distilled or very hot water.
- Sterilize or disinfect: pressure cooker (15 min at 15 PSI), dry-heat oven (160 °C, 2+ hours), or 70% isopropyl alcohol and air-dry. Never towel-dry.
- Sanitize containers with alcohol just before filling.
Shelf life, as given in the book
| Product | Shelf life |
|---|---|
| Cleanser, creams, toner | 9 months |
| Peptide serum, eye gel | 6 months |
| Facial oil | 9–12 months |
| Cleansing oil, shower gel | 12 months |
| Butters, scrubs, bath salts, firming gel | 6 months unopened · 3 opened |
Scale a formula
Enter a formula's weights and choose a new batch size. Percentages are calculated from the weights you enter. The tool loads the book's Calming Chamomile Foam Cleanser as an example.
| Ingredient | Original g | % | New g | Remove |
|---|
Original total0 g
New total0 g
Scaling soap?
Don't scale lye by hand. Re-enter the oils in a lye calculator for every batch size.
Knowledge articles
Formulation questions, answered
Formulation
Why is pH important in skincare?
Healthy skin's acid mantle sits at about pH 4.5–5.5. Products in that range protect the barrier, and pH also decides whether some actives and preservatives work.
The Big Book of Homemade Skin Care
Formulation
How do I adjust the pH of a formula?
Drop by drop, with a 10% acid solution to lower it or a 10% sodium hydroxide solution to raise it, checking after each addition.
The Big Book of Homemade Skin Care
Formulation
What is an emulsion, and how do I make a cream?
A cream is an oil-in-water emulsion: oil droplets held evenly through a water phase by an emulsifier. Both phases are heated to the same temperature and combined under high shear.
The Big Book of Homemade Skin Care
Formulation
What are the phases in a formula?
Groups of ingredients handled together at the same stage: water phase, oil phase, actives, preservative and pH adjustment.
The Big Book of Homemade Skin Care
Formulation
Why did my emulsion separate?
Almost always one of three things: the two phases were at different temperatures when combined, the emulsifier was under-dosed, or the mixing order was wrong.
The Big Book of Homemade Skin Care · The Big Book of Homemade Hair Care
Formulation
What's the difference between a serum and a cream?
The books don't define the terms side by side, but their formulas show the difference: the serum is a water-based gel, while the creams are emulsions of oil and water.
The Big Book of Homemade Skin Care
Formulation
What are active ingredients, and when do I add them?
Actives are the ingredients chosen for a specific effect, such as panthenol, peptides or niacinamide. Most are heat-sensitive, so they go into the cooling product at 38–40 °C.
The Big Book of Homemade Skin Care
Formulation
Do I need a preservative?
Any product containing water does. Anhydrous products (oils, butters, scrubs, bath salts) don't, as long as water never gets in.
The Big Book of Homemade Skin Care
Formulation
How do I make a gel without lumps?
Pre-disperse natural gums in glycerin before adding them to water, and sprinkle polymer powders slowly while stirring.
The Big Book of Homemade Skin Care