How to Make O/W Emulsions (Lotions & Creams)
Complete Guide to Oil-in-Water Emulsions
Oil-in-water (O/W) emulsions are the most common type of lotion and cream. In these formulations, tiny oil droplets are suspended throughout a continuous water phase, creating products that feel light, absorb quickly, and rinse off easily with water. This guide will teach you how to create stable, effective O/W emulsions using the SoapMath lotion calculator.
Unlike simple mixtures, emulsions require emulsifiers to bind oil and water together permanently. The lotion calculator includes a comprehensive ingredient database with built-in compatibility checking to help you create stable formulations every time.
Understanding O/W Emulsions
What makes it O/W?
Oil droplets are dispersed in water (the continuous phase). Think of it like tiny oil bubbles floating in water.
- Feels light and non-greasy
- Absorbs quickly into skin
- Rinses off with water
- Ideal for normal to oily skin
- Examples: body lotions, face creams, hand creams
Typical O/W formula structure:
- Water Phase (60-80%): Water, humectants, water-soluble actives
- Oil Phase (5-30%): Oils, butters, emulsifiers, oil-soluble actives
- Cool Down Phase (5-15%): Heat-sensitive ingredients added below 40°C
Safety and Sanitation
Water-containing products are breeding grounds for bacteria, yeast, and mold!
Preservation is NOT optional - it's essential for safety. The lotion calculator shows preservative coverage (bacteria, yeast, mold) to help you choose effective protection.
Sanitation protocols:
- Sanitize all equipment with 70% isopropyl alcohol
- Use distilled or deionized water (never tap water)
- Work on clean, sanitized surfaces
- Wear gloves when mixing (prevents contamination)
- Store in sanitized, airtight containers
Safety equipment:
- Safety glasses (when handling powders or hot liquids)
- Heat-resistant gloves for hot phases
- Mask when working with fine powders (rheology modifiers)
Equipment You'll Need
Essential equipment:
- Digital scale (accurate to 0.1g or 0.01g for small batches)
- Heat-safe beakers or containers (2 minimum - one for each phase)
- Double boiler or heat source
- Thermometer (infrared or probe)
- High-shear mixer: Stick blender (immersion blender) or homogenizer
- Spatulas (silicone or stainless steel)
- pH test strips or pH meter
- Storage containers (pump bottles, jars)
Optional but helpful:
- Pipettes for precise small additions
- Refractometer (for checking water activity)
Important: High-shear mixing required
Emulsions need high-shear force to properly disperse oil and water phases. A stick blender (immersion blender) or homogenizer is essential - manual whisking or milk frothers don't provide enough shear to create stable emulsions.
Step 1: Formulate with the Lotion Calculator
Navigate to the Lotion Calculator on SoapMath. The calculator will guide you through creating a balanced, stable formula with built-in safety checks.
1.1 Select Formulation Type
Choose O/W (Oil-in-Water) as your emulsion type.
This tells the calculator to show only ingredients compatible with O/W emulsions and filter out W/O-only options.
1.2 Choose Emulsifier Method
Select your emulsifier approach:
Complete Emulsifier System (Recommended for beginners):
Pre-blended systems like Emulsifying Wax NF, Polawax, BTMS-50, Olivem 1000. These contain everything needed and work at 2-5%.
The calculator shows which are complete systems.
HLB Matching (Advanced):
Calculate required HLB based on your oils, then select emulsifiers to match. The calculator provides HLB values for all emulsifiers.
For O/W emulsions, target HLB is typically 8-18.
1.3 Build Your Water Phase (60-80%)
Water (50-75%):
The base of your formula. Always use distilled or deionized water.
Humectants (3-10%):
Draw moisture to skin. The calculator shows 14 humectants including:
- Glycerin (3-5%): Classic, reliable
- Propylene Glycol (2-5%): Lighter feel
- Sodium Hyaluronate (0.1-2%): Luxurious hydration
- Panthenol (1-5%): Soothing, conditioning
Chelators (0.05-0.5%):
Recommended for stability, especially with tap water or minerals.
Important: The calculator will warn you if you add both a chelator AND minerals (like magnesium chloride) - chelators bind the minerals you want in your formula!
1.4 Build Your Oil Phase (5-30%)
Emulsifier (2-10%):
The calculator provides usage rates for 47 emulsifiers and 17 emulsifier blends.
- Complete systems: 2-5%
- Single emulsifiers: 5-10%
Oil Thickeners (0.5-5%):
Adds body and stability. The calculator shows 9 options:
- Cetyl Alcohol (1-3%): Light thickening
- Stearic Acid (2-5%): Pearlescent, thick creams
- Beeswax (1-3%): Natural thickener
Emollients (5-20%):
The calculator includes 38 emollients with polarity indicators (water-loving vs oil-loving):
- Light oils: Sweet Almond, Grapeseed (quick absorbing)
- Medium oils: Jojoba, Avocado (balanced)
- Rich oils/butters: Shea, Cocoa Butter (nourishing)
1.5 Build Your Cool Down Phase (5-15%)
Heat-sensitive ingredients added below 40°C (104°F):
Preservatives (0.5-1%): MANDATORY
The calculator tracks preservative coverage across four microbial categories (gram-positive bacteria, gram-negative bacteria, yeast, and mold) so you can verify your system is truly broad-spectrum:
- Phenoxyethanol blends: Calculator tracks total phenoxyethanol across all sources (including multi-component blends like Optiphen, Phenonip, Euxyl PE 9010) and warns if you exceed the 1% regulatory limit
- Paraben systems: Calculator warns if parabens are combined with cationic ingredients (BTMS, cetrimonium chloride) which deactivate them
- Acid-based systems: Sodium benzoate and potassium sorbate require pH below 5 — calculator checks your target pH
The calculator also checks for conflicts with ethoxylated surfactants (Polysorbate 20/80, Steareth, Ceteareth) which reduce phenoxyethanol effectiveness above 2%.
Antioxidants (0.05-0.5%):
Protect oils from rancidity. The calculator analyzes each oil's PUFA and MUFA content to calculate the exact antioxidant demand for your specific oil blend, then recommends proportional amounts for Vitamin E (T50 or T95), Rosemary Oleoresin Extract, Ascorbyl Palmitate, or BHT.
pH Adjusters (as needed):
Citric Acid, Lactic Acid to lower pH; Sodium Hydroxide, Triethanolamine to raise pH. Target pH: 4.5-6.0 for skin.
1.6 Review Calculator Warnings
The calculator automatically checks for:
- Chelator + mineral conflicts
- Electrolyte sensitivity issues
- pH incompatibilities
- Ionic charge conflicts (anionic vs cationic)
- W/O restrictions (ingredients not suitable for O/W)
Step 2: Prepare Your Workspace
- Sanitize everything - Spray equipment with 70% alcohol, let dry
- Set up your phases - Two beakers ready (water phase, oil phase)
- Measure ingredients - Weigh each ingredient precisely
- Organize cool-down ingredients - Have them ready in separate containers
- Prepare ice bath - For cooling if needed
Step 3: Heat Both Phases
Water Phase:
- Combine water, humectants, and water-soluble ingredients in beaker
- Heat to 160-180°F (71-82°C) using double boiler
- Stir occasionally to ensure even heating
- Dissolve any powders completely
Oil Phase:
- Combine oils, emulsifier, and oil-soluble ingredients in separate beaker
- Heat to 160-180°F (71-82°C)
- Stir until all solid ingredients melt completely
- Ensure emulsifier is fully dissolved
Temperature matching is critical:
Both phases should be within 5°F of each other before combining. Temperature shock can prevent proper emulsification.
Step 4: Combine the Phases
- Check temperatures - Both phases at 160-180°F and within 5°F of each other
- Pour oil phase into water phase (never reverse this!)
- Begin mixing immediately using stick blender
- Blend for 1-3 minutes until emulsion forms
- - Start slow to avoid splashing
- - Increase speed gradually
- - Keep blender submerged to avoid bubbles
- Watch for emulsion formation
- - Mixture will change from separated to unified
- - Color becomes consistent throughout
- - Texture thickens and smooths
What you'll see:
- Initially: Two distinct layers
- After 30 seconds: Cloudy mixture forming
- After 1-2 minutes: Smooth, creamy emulsion
- Fully emulsified: Uniform color and texture
Step 5: Cool and Add Heat-Sensitive Ingredients
- Continue stirring while mixture cools (prevents skin formation)
- Cool to 40°C (104°F) or below
- - Natural cooling: 20-40 minutes with occasional stirring
- - Ice bath: 10-15 minutes (faster but requires constant stirring)
- Add cool-down ingredients:
- - Preservative first (mix thoroughly)
- - Antioxidants (if using)
- - Fragrance/essential oils last
- Mix gently after each addition (30-60 seconds)
- Continue cooling to room temperature (20-25°C)
Why cool before preservatives?
Many preservatives degrade above 40°C. Adding them too early reduces their effectiveness. Always check your preservative's temperature limit.
Step 6: pH Testing, Adjustment, and Bottling
pH Testing:
- Test pH once lotion reaches room temperature
- Target pH: 4.5-6.0 for face products, 5.0-7.0 for body
- If needed, adjust:
- - Too high: Add citric acid solution (10% in water) drop by drop
- - Too low: Add sodium hydroxide solution (20% in water) drop by drop
- Mix thoroughly and retest after each adjustment
Bottling:
- Transfer to sanitized containers
- Pump bottles work best (minimize contamination)
- Fill to 90% capacity (leave headspace)
- Label with ingredients, date, and pH
Final thickness note:
Lotion will continue to thicken for 24-48 hours as it fully cools and stabilizes. Don't judge final texture immediately!
Troubleshooting O/W Emulsions
| Problem | Cause | Solution |
|---|---|---|
| Won't emulsify/stays separated | Not enough emulsifier, wrong temperature, or incompatible ingredients | Increase emulsifier to 5-8%; ensure both phases 160-180°F; check calculator warnings for conflicts |
| Separates after cooling | Emulsifier incompatibility, electrolyte issue, or mineral conflict | Review calculator warnings; remove chelator if using minerals; check for ionic conflicts (cationic + anionic) |
| Too thin/watery | Too much water phase or not enough thickeners | Add rheology modifier (0.1-0.5% xanthan gum) or increase oil-phase thickeners (cetyl alcohol, stearic acid) |
| Too thick/pasty | Too much emulsifier or thickeners | Reduce emulsifier to 3-4%; reduce thickeners; or add more water phase (must reblend hot) |
| Grainy texture | Emulsifier not fully melted or recrystallization | Ensure full melt at 160°F+; some emulsifiers naturally crystallize (this is normal for BTMS) |
| Lumpy or clumpy | Rheology modifier clumping or poor dispersion | Pre-disperse xanthan/carbomer in glycerin before adding; mix more thoroughly |
| Oil slick on surface | Not enough emulsifier or oil added after emulsification | Increase emulsifier by 1-2%; ensure all oils added before emulsification |
| Mold or contamination | Insufficient preservative, added too hot, or contaminated equipment | Use 0.8-1% broad-spectrum preservative; add below 40°C; sanitize all equipment; discard contaminated batch |
| Lotion "broke" after days/weeks | pH drift, temperature fluctuation, or incompatible ingredients reacting | Test pH regularly; store at stable temperature; avoid ingredient combinations flagged by calculator |
| Strange smell developed | Oils going rancid or microbial growth | Add antioxidant (Vitamin E 0.5%); ensure adequate preservative; store in cool place; discard if rancid |
Tips for Success
For your first batch:
- Use a complete emulsifier system (Emulsifying Wax NF or Polawax at 4-5%)
- Make small batch (100-200g) to test texture
- Follow calculator warnings carefully
- Keep formulation simple (water, glycerin, oils, emulsifier, preservative)
- Take notes on what works
Storage and stability:
- Store at room temperature (15-25°C) away from heat/light
- Use within 3-6 months (with proper preservation)
- Monitor for changes in smell, color, or texture
- Do stability testing (1 week at room temp, 1 week refrigerated, 1 week at 40°C)
Pro tips:
- Let the calculator guide you - its warnings prevent most failures
- Temperature control is more important than mixing speed
- Always add oil to water (never reverse)
- Preservation is non-negotiable - never skip it
- Label everything with date and pH
Frequently Asked Questions
Tip: Use the Help Me Pick Ingredients Wizard
Not sure which humectants, emollients, or actives to use? The Help Me Pick Ingredients wizard in the Lotion Calculator recommends ingredients and percentages based on your skin concern, texture preference, and product type. It includes natural and vegan filters.