Why SLS flakes and clouds when adding salt to thicken it?

When pouring salt to try to thicken

water 90%
SLS powder 10% (it's SLS, Sodium Lauryl Sulfate and not SLES)

It forms some white "flakes" where the salt solution drop fell, these "flakes" take a few minutes of stirring to completely disappear
and it doesn't seem to thicken and it becomes cloudy when too much salt (about 1% NaCl ) was added.

Is that normal for SLS?


  • PerryPerry Administrator, Professional Chemist
    Yes, I think that is normal for SLS. At least that was what happened with the VO5 shampoo formulas.  Although we used a 30% solution of SLS, not powder.

    SLS has a salt curve in which salt will either thicken or thin the system.
  • So I guess that's why you don't hear about SLS being used solo?
    By the way I considered using SLS in HI&I products as an alternative to alkylbenzene sulfonates.

    Also by using copolymers, such as those envisaged by U.S. Pat. No. 4,423,199, containing from 20 to 25 weight percent of N-alkyl acrylamide units, it is possible to increase the viscosity of certain surfactants in solution, such as sodium lauryl sulfate at a concentration of 8 percent, but the texture of the resulting gels is too stringy on discharge and is not therefore practically suitable.

    Anionic surfactant compositions such as sodium laureth (2EO) sulfate (SLES)/cocodiethanolamide (CDEA) provide a wide viscosity/salt curve that is only moderately salt sensitive and is about 3.5% salt tolerant, Figure 1. Ammonium lauryl sulfate (ALS) compositions, however, have a higher narrower viscosity/salt curve with a significantly lower salt tolerance of about 0.6%, Figure 2.

    Use of anionic compositions, particularly with ALS containing compositions at high active ingredient levels and those containing amphoterics such as betaines, develop very high nonpourable viscosities that generally require thinning agents to lower viscosity.
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