Process
Phase Order in DIY Emulsions
Step-by-step process for making stable cream and lotion emulsions. Heat phases, when to add what, why order matters.
The 5 phases of an emulsion
| Phase | What goes in | Temperature | Why it matters |
|---|---|---|---|
| 1. Water phase | distilled water, hydrosols, glycerin, humectants, water-soluble actives that tolerate heat | Heat to 70-75°C, hold 20 min | Water needs to be heated to dissolve thickeners + reduce microbial load |
| 2. Oil phase | carrier oils, butters, fatty alcohols (cetyl, cetearyl), emulsifying wax | Heat to 70-75°C, hold 20 min | Emulsifying wax + butters need to fully melt |
| 3. Emulsion | Combine phases at the same temperature with continuous stirring or stick-blending for 2-3 min | Both at 70-75°C | Same temp = stable emulsion; temperature mismatch = breaking |
| 4. Cool-down | Heat-sensitive actives, fragrance, preservative, vitamin E, niacinamide, panthenol | When mix cools to 40°C or below | Adding earlier degrades these ingredients |
| 5. pH adjust | Citric acid (lowers) or sodium hydroxide (raises) | Room temperature | Most formulas target pH 4.5-6.0 |
Heat-and-hold — what it does
Heating both water and oil phases to 70-75°C and holding for 20 minutes does three things:
- Melts all the emulsifying wax — incomplete melting = unstable emulsion
- Dissolves all water-phase thickeners and humectants
- Reduces microbial load in the water (significant — distilled water is not sterile)
Skipping heat-and-hold (the “shortcut method”) works for some formulas but is the #1 cause of unstable lotions for beginners. Take the 20 minutes.
What to add at cool-down (BELOW 40°C)
Add these AFTER the emulsion has cooled to 40°C or less:
- Preservatives — most degrade or evaporate above 40°C (especially Liquid Germall Plus, Geogard ECT, Plantaserve E/P)
- Vitamin E (tocopherol) — antioxidant degrades with prolonged heat
- Vitamin C derivatives — heat-sensitive
- Retinol / retinaldehyde — destroyed by heat
- Panthenol — best preserved cool
- Niacinamide — generally heat-tolerant but cool-down works better
- Essential oils and fragrance — volatile, evaporate with heat
- Hyaluronic acid — pre-hydrate separately, add at cool-down
- Hydrolyzed proteins — heat-sensitive
- Live botanical extracts — most prefer cool-down
- Ceramides — best below 50°C
What MUST go in the hot phase
- Emulsifying wax (the whole point of heating)
- Cetyl alcohol, cetearyl alcohol, stearyl alcohol — must melt
- Cocoa butter, shea butter, mango butter — must melt evenly
- Beeswax, candelilla wax, carnauba wax — must melt
- Liquid carrier oils — heat with oil phase even though they don’t strictly need to melt
- Gum thickeners (xanthan, sclerotium) — dissolve in hot water
When to use cold-process emulsification
Some emulsifiers (Sucragel, Olive Crystal Wax derivatives, some glucoside surfactants) tolerate cold-process — no heat needed. Useful for:
- Heat-sensitive actives where you want zero degradation
- Quick small-batch testing
- Eye-area products where antioxidant preservation matters most
Most “natural” oil-in-water emulsifiers still need heat. Always check your emulsifier’s spec sheet.
Stirring vs stick-blending
- Hand-whisking only: works for soft creams with simple emulsifiers (Polawax). Stir continuously for 5+ minutes after combining phases.
- Stick blender (immersion blender): required for stable lotions with most emulsifiers. Pulse 30 seconds on, 30 seconds off, for 3-5 minutes total. Don’t over-mix (incorporates too much air).
- High-shear mixer (homogeniser): for fine-particle, “luxury” emulsions. Overkill for most home formulas.
Trouble-shooting the emulsion
| Symptom | Likely cause | Fix |
|---|---|---|
| Watery / breaks within hours | Phases combined at different temps | Same temp + immediate stick-blend |
| Grainy texture | Butter/wax not fully melted | Re-heat to 75°C and re-emulsify |
| Separates over days | Insufficient emulsifier | Increase to 6-8% of total |
| Becomes too thick on cool-down | Too much cetyl/cetearyl alcohol | Reduce to 1-2% |
| Stays runny | Not enough thickener / wrong emulsifier | Add 0.3% xanthan gum or change emulsifier |
pH adjustment timing
Always adjust pH at the end, room temperature, AFTER all actives are in.
- Too acidic → add 10% sodium hydroxide solution dropwise
- Too alkaline → add 50% citric acid solution dropwise
- Test with pH strips between 2-7 or a calibrated pH meter
Target ranges:
- Face cream / serum: 4.5-6.0
- Body lotion: 5.0-6.5
- Hair conditioner: 4.0-5.0 (slightly acidic = smooth cuticle)
- Shampoo: 4.5-6.0
- Wash-off cleanser: 5.0-7.0
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