How to Make W/O Emulsions (Barrier Creams)
Complete Guide to Water-in-Oil Emulsions
Water-in-oil (W/O) emulsions are the opposite of traditional lotions - tiny water droplets are suspended in a continuous oil phase. These rich, protective formulations create a barrier on skin that locks moisture in and keeps irritants out. They're ideal for very dry skin, barrier creams, and protective products.
W/O emulsions require special emulsifiers and techniques different from O/W formulations. The SoapMath lotion calculator filters ingredients specifically for W/O compatibility and warns about restrictions to ensure your formulation succeeds.
Understanding W/O Emulsions
What makes it W/O?
Water droplets are dispersed in oil (the continuous phase). Think of it like water bubbles floating in oil.
- Feels rich and occlusive
- Sits on skin surface (slower absorption)
- Water-resistant and protective
- Ideal for very dry, damaged, or barrier-compromised skin
- Examples: barrier creams, diaper rash ointments, protective hand creams
Typical W/O formula structure:
- Water Phase (20-40%): Water, humectants, water-soluble actives
- Oil Phase (60-80%): Oils, butters, W/O emulsifiers, oil-soluble actives
- Cool Down Phase (3-10%): Preservatives, antioxidants, fragrance
Key differences from O/W:
- Requires W/O-specific emulsifiers (HLB 3-8)
- Water added to oil (reverse of O/W)
- Many O/W ingredients won't work (calculator filters these out)
- Naturally thicker and richer texture
Safety and Sanitation
W/O emulsions still contain water - preservation is mandatory!
Even though oil is the continuous phase, the water droplets can harbor bacteria, yeast, and mold. The lotion calculator shows which preservatives work in W/O systems.
Sanitation protocols:
- Sanitize all equipment with 70% isopropyl alcohol
- Use distilled or deionized water only
- Work on clean surfaces with gloves
- Store in airtight, sanitized containers
Equipment You'll Need
Same equipment as O/W emulsions:
- Digital scale (accurate to 0.1g)
- Heat-safe beakers (2 minimum)
- Double boiler or heat source
- Thermometer
- High-shear mixer: Stick blender (immersion blender) or homogenizer
- Silicone spatulas
- pH strips or meter
- Storage containers
Important: High-shear mixing required
W/O emulsions especially need high-shear force to properly disperse water droplets in the oil phase. 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 and select W/O formulation. The calculator automatically filters ingredients to show only W/O-compatible options.
1.1 Select Formulation Type
Choose W/O (Water-in-Oil) as your emulsion type.
The calculator will hide O/W-only ingredients and show W/O restrictions. Many popular ingredients (like certain emulsifiers and rheology modifiers) won't appear because they don't work in W/O systems.
1.2 Choose Emulsifier Method
W/O emulsifiers have low HLB values (3-8). The calculator offers two methods:
W/O Emulsifier Blends (Easiest):
Pre-made W/O emulsifier systems that automatically calculate the correct amount based on your water phase percentage.
The calculator uses a tiered system: higher water content requires more emulsifier for stability. For example:
- 5-15% water → ~2.75% emulsifier
- 15-30% water → ~3.6% emulsifier
- 30-50% water → ~5.2% emulsifier
- 50-75% water → 7-9.5% emulsifier
W/O HLB Method (Advanced):
Combine primary and secondary emulsifiers in a 70/30 ratio. The calculator identifies which emulsifiers work as primary (can work alone) vs secondary (co-emulsifiers that enhance stability).
Primary emulsifiers: Glyceryl Stearate, Sorbitan Oleate, PEG-30 Dipolyhydroxystearate
Secondary emulsifiers: Lecithin, Glycol Stearate, Ceteth-2
Common W/O emulsifiers:
- Sorbitan Oleate (HLB 4.3) - Primary
- Glyceryl Stearate (HLB 3.8) - Primary
- PEG-30 Dipolyhydroxystearate (HLB ~5) - Primary
- Lecithin (HLB 4-9) - Secondary
Traditional Method: Beeswax + Borax
A classic natural emulsifier system that creates stable O/W emulsions (note: despite being discussed in W/O guides, this actually creates oil-in-water emulsions).
How it works:
- Beeswax (2-5%) goes in the oil phase
- Borax (0.5-1% of beeswax weight, typically 0.1-0.25% of total formula) goes in the water phase
- Borax reacts with beeswax acids to form an emulsifier in situ
- Results in thick, rich creams with a natural feel
Example: 3% beeswax in oil phase + 0.15% borax in water phase (0.5% of beeswax weight)
1.3 Build Your Water Phase (20-75% max)
Water (15-70%):
W/O emulsions can incorporate up to 75% total water phase, though most formulations use 20-40%. The calculator automatically adjusts emulsifier amounts for higher water content.
Always use distilled water.
Humectants (3-8%):
Same as O/W, but use less total:
- Glycerin (2-5%)
- Propylene Glycol (2-4%)
- Panthenol (1-3%)
W/O Restrictions:
The calculator marks ingredients that don't work in W/O. Electrolyte-sensitive emulsifiers and certain rheology modifiers (xanthan gum, carbomer) won't appear for W/O formulations.
1.4 Build Your Oil Phase (60-80%)
W/O Emulsifier (Auto-calculated):
The calculator automatically determines the correct emulsifier amount based on your water phase percentage using manufacturer-recommended formulations.
Simply select your W/O emulsifier blend or use the HLB method - the calculator handles the percentages to ensure stability.
Oils & Butters (40-65%):
W/O emulsions work well with heavy oils and butters:
- Shea Butter (10-30%): Rich, protective
- Cocoa Butter (5-15%): Firm barrier
- Lanolin (5-15%): Excellent W/O emulsifier/emollient
- Dimethicone (5-20%): Silky, water-resistant
- Castor Oil (5-15%): Glossy finish
Waxes (2-8%):
Add structure and stability:
- Beeswax (2-5%): Natural thickener
- Candelilla Wax (1-3%): Vegan alternative
1.5 Build Your Cool Down Phase (3-10%)
Preservatives (0.5-1%): MANDATORY
Not all preservatives work in W/O. The calculator shows compatible options:
- Phenoxyethanol blends (check percentage limits in calculator)
- Optiphen Plus (0.75-1.5%)
- Germall Plus (0.1-0.5%)
Antioxidants (0.05-0.5%):
Vitamin E, Rosemary Extract (prevent oil rancidity)
Fragrance (0.5-2%):
Oil-soluble fragrances work best in W/O
1.6 Review Calculator Warnings
For W/O emulsions, the calculator checks:
- W/O compatibility (filters out incompatible ingredients)
- Phase inversion risks
- Preservative compatibility
Step 2: Prepare Your Workspace
- Sanitize everything - Equipment, containers, work surface
- Set up phases - Two beakers (water phase, oil phase)
- Measure ingredients - Weigh precisely
- Organize cool-down - Have preservatives ready
Step 3: Heat Both Phases
Water Phase:
- Combine water and humectants in beaker
- Heat to 160-180°F (71-82°C)
- Stir to ensure complete dissolution
- Check and adjust pH if needed - Target pH 5.5-6.5 before emulsifying
Important: pH adjustment before emulsifying
Always check and adjust the pH of your water phase before combining with the oil phase. Once emulsified, pH adjustment becomes difficult and can destabilize the emulsion.
Oil Phase:
- Combine oils, butters, waxes, and W/O emulsifier
- Heat to 160-180°F (71-82°C)
- Stir until everything melts completely
- Ensure emulsifier is fully dissolved
Temperature matching:
Both phases must be within 5°F of each other and at proper temperature (160-180°F) before combining.
Step 4: Combine the Phases (REVERSE of O/W!)
CRITICAL: For W/O, add WATER to OIL
This is the opposite of O/W emulsions! Adding oil to water will create O/W instead.
- Check temperatures - Both at 160-180°F, within 5°F
- Pour water phase into oil phase slowly
- Begin mixing immediately with stick blender
- Blend for 2-4 minutes until emulsion forms
- - Start slow, increase gradually
- - Keep blender submerged
- - W/O takes slightly longer to emulsify than O/W
Emulsion formation in W/O:
- Initially: Oily with water pockets
- After 1 minute: Starting to thicken
- After 2-3 minutes: Thick, creamy, uniform
- Fully emulsified: Rich, smooth cream
Step 5: Cool and Add Preservatives
- Continue stirring while cooling
- Cool to 40°C (104°F) or below
- Add preservative and mix thoroughly
- Add antioxidants and fragrance if using
- Continue cooling to room temperature
W/O thickening:
W/O emulsions thicken significantly as they cool. Don't be alarmed if it becomes very thick - this is normal and expected.
Step 6: pH Testing and Bottling
pH Testing:
- Test pH at room temperature
- Target pH: 5.0-6.5
- Adjust if needed (same as O/W)
Bottling:
- Transfer to sanitized jars (W/O works better in jars than pumps)
- Fill to 90% capacity
- Label with ingredients, date, and pH
W/O creams continue to firm up for 48-72 hours. Final texture assessment should wait until fully set.
Troubleshooting W/O Emulsions
| Problem | Cause | Solution |
|---|---|---|
| Won't emulsify | Wrong emulsifier type, insufficient amount, or temperature issues | Verify W/O emulsifier (check calculator); increase to 5-8%; ensure both phases 160-180°F |
| Became O/W instead (phase inversion) | Added oil to water OR used O/W emulsifier | Always add water to oil for W/O; use only W/O-compatible emulsifiers from calculator |
| Separated after cooling | Incompatible preservative or not enough emulsifier | Use W/O-compatible preservative (check calculator); increase emulsifier by 1-2% |
| Too greasy/heavy | High oil phase or heavy oils/butters | This is normal for W/O! Reduce butters/waxes; add lighter oils; or slightly increase water phase |
| Extremely thick/solid | Too much wax/butter or natural thickening of W/O emulsifier | Reduce waxes to 2-4%; reduce butters; some W/O emulsifiers naturally create very thick creams |
| Grainy/gritty texture | Wax or butter crystallization | Ensure complete melt at 160-180°F; cool slowly with stirring; some crystallization is normal |
| Water beading on surface | Not fully emulsified or water added too quickly | Blend longer (3-5 minutes); add water phase more slowly; ensure proper temperature |
| Developed mold | Insufficient or incompatible preservative | Use W/O-compatible preservative at 0.8-1%; ensure added below 40°C; discard contaminated batch |
Tips for Success
For your first W/O batch:
- Let the calculator filter ingredients - it will only show W/O-compatible options
- Use a complete W/O emulsifier blend at 5-7%
- Remember: water into oil (opposite of O/W!)
- Start with 30% water, 70% oil phase
- Accept the rich, heavy texture - it's correct for W/O!
When to use W/O:
- Very dry, damaged, or compromised skin barriers
- Protective barrier creams (outdoor work, diaper area)
- Water-resistant applications
- Occlusive night treatments
- When you need a product that stays on skin surface
Pro tips:
- Trust the calculator's W/O filtering - it prevents incompatibility issues
- W/O naturally feels richer - this is the point, not a flaw
- Temperature control prevents phase inversion
- Water to oil - remember this!
- Preservation is still mandatory despite oil phase dominance
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.