Shampoo color change and getting thin problem.

Hi guys, I need your advice for my shampoo problem. I have philosophy of making my products without colorant at all, but it seems the color change always happened. My formula is as below:

A To 100 Water 
A 0.1 Glycerin
A 0.1 d-Panthenol
A 0.2 Disodium EDTA
A 3 Polyquarternium-7
B 14.3 Sodium Lauryl Ether Sulfate (70%) – 10% active
B 10 Cocamidopropyl Betaine (30%) – 3% active
B 0.5 Decyl Glucoside
B 0.5 PEG-7 Glyceryl Cocoate
B 0.5 Glycol Distearate
C 0.5 PEG-40 Hydrogenated Castor Oil
C 1 Dipropylene glycol
C 1 Polysorbate 20
C 1 Fragrance 
D 0.5 Kemidant L Plus (DMDM Hydantoin + Iodopropylnyl butylcarbamate)
D 0.9 Salt

I have 2 main problem with my formula here. Please not that I kept my product at room temperature, no direct to sunlight

1. The day when I finished making this, it is pure white (no sign of yellow tint at all). However, around 1-2 week later, I compared to the new one I made, the color is slight yellowish. (Although if we do not compare side by side, the yellowish product actually can't be noticed that it has changed color. But if we place it side by side with the freshly made one, it is indeed different).

2. In my formula, I only use salt as the sole thickener. Again first day it is thick and good. However, 1-2 weeks later, I can notice it is thinning and not as thick as the first day it was.
Do salt thickening effect cannot last for 1-2 years?

Thank you and hope to hear your experience guys. 
Warm regards,
Vincent

Comments

  • PerryPerry Administrator, Professional Chemist
    edited March 2021
    What happens to the pH over time?

  • @Perry hi Perry thanks for your reply. I don't have accurate pH meter so I use litmus paper to check the pH. Although the color really changed a lot, from white to yellow/greenish olive, but the pH remains around 5.0-5.5. 
    However, I still want to add buffer solution, just in case in period 1 year after when there is pH drift, it will be safe with that buffer.

    Can you teach me how to make easy buffer solution?
    Is 0.2% sodium citrate will work, and at what pH will it maintain the product?

    Thank you and looking forward for your advise 
  • I suspect the cause is due to Hydrolysis of Polysorbate 20 and PEG-40 Hydrogenated Castor Oil. 

    I have experience with PEG-80 sorbitan laurate that will undergo hydrolysis and change color to yellow even at room temperature.
  • @MetalizeMerz do you think i need to remove either 1 of it, or both? Actually i can remove both, because i'm not trying to achieve crystal clear product. But i just want them both to be in my ingredients as they work as good solubilizer and superfatting agent.
  • PEG-7 Glyceryl Cocoate is the only superfatting agent in your formula from my view.
    I just suggest to remove PEG-40 Hydrogenated Castor Oil and Polysorbate 20 in order to confirm the cause of your formula color change.
    (in some case color change is due to impurities from your material also).
  • Bill_TogeBill_Toge Member, Professional Chemist
    the level of polyquaternium-7 (a cationic in a mostly anionic system) seems high, try reducing it
    also, what's the purpose of the dipropylene glycol? glycols, particularly longer-chain ones, thin surfactant systems

    UK based cosmetic chemist with 13 years' experience at the bench. I've worked with pretty much everything apart from pressed powders, soap, solid lipstick and aerosols.
  • @Bill_Toge Thanks for your feedback. My polyquatz-7 active content is 20%. I think it is reasonable right?

    About dipropylene glycols, Yes I know it will cause thinning. But I have tried this, and the salt thickening effect is great enough to achieve the viscosity i desired. The reason i put dipropylene glycol is for plasticizer/enhance the fragrance since it is crucial in my market (we prefer strong aroma). I hope with this dipropylene glycol addition, the fragrance will linger on skin for longer time even after rinse-off. What do you think?

    Thanks so much
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