Why Won't My Cleanser Thicken?
Salt thickening, why it fails, and what to use instead
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Adding salt to thicken a surfactant formula is a classic technique, but it only works if your surfactant blend is responsive. When it fails, no amount of salt will help. This guide explains why.
How Salt Thickening Works
Surfactants organize into micelles. Electrolytes (salt) change these from spherical to worm-like structures that entangle, increasing viscosity.
Critical Requirement
Salt thickening only works with anionic surfactant systems (primarily SLS/SLES). Other types do not respond to salt.
When Salt Thickening Fails
Non-anionic Primary Surfactant
Glucosides, betaines used alone, and succinates do not salt-thicken. Use polymer thickeners instead.
Low ASM Concentration
Below 10–12% ASM, micellar density is too low for entanglement. Check your score in BubbleMath.
Passed the Peak
Every formula has a peak salt concentration. Adding more beyond that point actually thins the product.
Structure Disruption
High glycerin, oils, silicones, or botanical extracts can interfere with the micellar network.
Responsive Blends
- SLES + CAPB (3:1 ratio): The gold standard for thickening.
- SLS + CAPB: Similar high response, though harsher on skin.
- Sodium Lauroyl Sarcosinate: Moderate salt response, very gentle.
BubbleMath Tip
BubbleMath shows each surfactant's salt thickening rating and flags viability. If it's yellow or red, salt won't work.
Polymer Thickeners
Use these for sulfate-free or glucoside-based cleansers:
- Crothix: Specifically designed for surfactants. Easy to use at 1-3%.
- HEC (Hydroxyethylcellulose): Add to water phase first. Gives non-tacky gels.
- Carbomer: Requires pH neutralization. Sensitive to electrolytes.
Frequently Asked Questions
Check thickening viability in BubbleMath
BubbleMath predicts whether your blend will thicken with salt before you start mixing.