Home Cosmetic Science Talk Formulating Shampoo getting sharp crystals when reducing pH

  • Shampoo getting sharp crystals when reducing pH

    Posted by drsimranjit_lv on July 10, 2024 at 6:45 am

    I was making a shampoo with the following formula:

    Aqua 35.90

    Disodium EDTA 0.10

    Glycerin 3.00

    Glycereth-26 2.00

    Hydroxypropyl Methylcellulose


    PEG-45M 0.50

    Cyamopsis Tetragonoloba (Guar) Gum 0.40

    Sodium Cocoyl Glycinate 10.00

    Cocamidopropyl Hydroxysultaine 5.00

    Sodium Cocoamphoacetate 4.00

    Glycol Distearate 2.00

    Decyl Glucoside 1.50

    Sorbeth-230 Tetraoleate (and) Decyl Glucoside (and) Sorbitan Laurate 0.80

    Quaternium-95 (and) Propanediol 2.00

    Polyquaternium-7 0.1

    Phenoxyethanol 1.00

    Panthenol 0.50

    Water (and) Alpha-Glucan Hydroxypropyltrimonium Chloride (and) Propylene Glycol 0.30

    Hydrolysed Quinoa 0.10

    Glycerin 1.00

    Methyl Gluceth-20 2.00

    Polyquaternium-10 0.20

    Amodimethicone (and) Trideceth-12 (and) Cetrimonium Chloride 2.00

    Fragrance 2.00

    Saccharide Isomerate (and) Aqua (and) Citric Acid (and) Sodium Citrate 0.50

    Phenoxyethanol (and) Benzoic Acid (and) Dehydroacetic Acid 0.50

    Citric Acid 1.00

    and when I reached pH = 6, the shampoo started to get sharp, abrasive crystals. Why did this happen and how do i fix it?

    chemist-chef replied 6 days, 22 hours ago 2 Members · 1 Reply
  • 1 Reply
  • chemist-chef

    July 10, 2024 at 9:57 pm


    I assume you need to reduce the pH of this shampoo because the preservative system that you use (Phenoxyethanol (and) Benzoic Acid (and) Dehydroacetic Acid) only effective under pH 6.5.

    My question is : why you use 2 preservatives (both contain phenoxyethanol) in one formulation? Phenoxyethanol 1% and Phenoxyethanol+Benzoic Acid+Dehydroacetic Acid blend 0.5%?

    But I’m not so sure the crystallization occur in your formulation because of the pH.

    I see the incompatibility between surfactant and conditioning agent that you use in this shampoo.

    You use anionic surfactant Sodium Cocoyl Glycinate (10%) and cationic conditioning agent Amodimethicone, Cetrimonium Chloride, Alpha-Glucan Hydroxypropyltrimonium Chloride, Quaternium-95. And also Cyamopsis Tetragonoloba (Guar) Gum that tends to have better compatibility with cationic materials. I assume the crystallization occurs because of this anionic-cationic incompatibilities.

    My suggestions:

    - if you still want to use these cationic conditioning agents, you can
    replace the anionic surfactant and use only nonionic and amphoteric
    surfactants. But if you have no anionic surfactant at all in cleansing formulation, i guess the
    cleansing ability of this shampoo will be not as good as if you use
    anionic surfactant, since anionic surfactants are the surfactant with best cleansing ability.

    - you can replace these cationic conditioning agent with Polyquartenium-7. PQ-7 is also cationic, but has much better compatibility with anionic surfactant.

    Please correct me if my answer is wrong.

    Thank you

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