How much to dilute 70% SLES gel so it becomes liquid?

Dilute it by half, down to 35%? 30%
Do you need a preservative when it becomes liquid?


  • em88em88 Member
    There are commercial SLES solutions at 26-27% which are liquids. My guess it should be liquid even at 35%, but it should be tested. 
    Regarding preservatives, I've seen without, but I guess it depends on the shelf life. 
  • Bill_TogeBill_Toge Member, Professional Chemist
    between around 30 and 65% w/w it forms a crystalline phase which is completely rigid, and much harder to process than the lamellar phase it forms at 70% and above - this is why it's sold as 70%, 28% or lower

    whether or not it needs preservatives depends on the pH of the dilution; dilutions without preservatives are around pH 12, and use their high alkalinity as preservation

    in my experience, industrial-scale dilution tends to be carried out using a specialist (and complex) Bran-Luebbe mixer like this one

    UK based formulation chemist. Strongest subjects: hair styling, hair bleaches, hair dyes (oxidative and non-oxidative) I know some stuff about: EU regulations, emulsions (O/W and W/O), toothpaste, mouthwash, shampoos, other toiletries
  • FekherFekher Member, Professional Chemist
    @Gunther for sure it needs preservative
  • When SLES70% is converted into SLES27%, it diluted by a lot of water,
    At the same time the osmolarity of the solution decreases, due to a lower concentration of salts,
    Which gives room for bacterial growth.

    In my factory we consume large quantities of SLES70%, and sometimes in the winter we use SLES27%.
    Solutions of SLES27% are manufactured according to factory orders and are with the same preservation system as the plant uses and at its request.

    Chief Chemist/ R&D Manager at SASA Cosmetics
  • Bill_toge is right, at around 30% in water SLES form an hexagonal liquid crystalline phase that is very viscous. The concentration limits of the phases may vary a lot depending the impurities contained in the different batches of SLES.  I guess that the hexagonal phase is present in a large range of temperature (is is the case for SDS not sure with SLES).
  • @jeremien so that means that SLES is still viscous at 30%, so you'd need to dilute it down to 27% or less for it to become water-thin ?
  • @jeremien yes, SLES will also get gummy at low temp. Specially the natural type. 

    @Gunther that's why is usually sold at 25%, it remains liquid. If you are buying higher concentration, if the supplier doesn't give you the COA is usually watered down.
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