The “Salt Trick”
Everyone knows the cheapest way to thicken SLES (AES) is salt.
Common table salt (Sodium Chloride). Or sometimes Sodium Sulfate.
You add salt. The liquid gets thick like honey. It looks expensive.
But here is the trap.
The Salt Curve: A Dangerous Hill
Imagine a hill.
You start at the bottom. You add salt. You climb up the hill. Viscosity goes up.
You reach the top. This is the maximum thickness.
What happens if you keep adding salt?
You don’t stay at the top. You fall down the other side.
The liquid becomes thin like water again.
And worse: it becomes cloudy and white.
We call this “salting out.”
Why Does This Happen?
Without getting too technical:
Surfactants form structures called “micelles” (tiny balls).
Salt makes these balls pack tighter together. That’s thickness.
But too much salt makes the balls collapse or separate from the water.
Once you cross the peak, you cannot go back easily.
How to Find the Sweet Spot
Every formula has a different “peak.”
If you change the SLES brand, the peak changes.
If you add more fragrance, the peak changes.
The Old Master’s Method:
- Take 100g of your base formula.
- Add salt 0.1g at a time.
- Stir and measure thickness.
- Write it down.
- Stop when it gets thinner.
Now you know the limit. In production, use slightly less than the limit.
Common Mistakes
Mistake 1: Dumping salt in all at once.
You might overshoot the peak instantly.
Mistake 2: Using dirty salt.
Industrial salt often has iron. Iron makes SLES yellow.
Use refined salt. It costs pennies more but saves your color.
Mistake 3: Not dissolving the salt.
If you throw solid salt into thick shampoo, it takes forever to dissolve.
Make a saturated salt water solution first. Add the liquid salt water. It mixes faster.
The Bottom Line
Salt is cheap, but dangerous.
Know your curve.
Find the peak in the lab first.
And never, ever add “just a little more” without testing. Once it turns to water, you can’t fix it.
