Maintaining pH for shampoo

vhogiono

Hi guys, i want to ask about maintaining pH in a surfactant formula. Actually this is for avoiding changing of color like what I have posted in previous discussion. But i decided to post a new one, because this is different topic.

I looked in the internet, that one of the cause color changing in surfactant is due to pH drifting. I learned from IPCS (institute personal care of science), and they said too acidic will turn into pink, and too alkaline will turn into greenish. And during 2-3 years of product life span, the pH can drift +/- 10% from its origin. 

I have questions as below:
1. Is there any way to keep the pH of the product stable?
2. What cause the pH drift much? (is there any relation with storage keeping, temperature, humidity?)
3. IPCS mentioned very little about something called "buffer" to keep the pH steady. But I did not get any good explanation and detail about this. Do we really need to make buffer solution for a simple shampoo/bodywash product? How do we make this buffer solution?

Thank you guys, and sorry for the many questions I have. Really hope to hear your insight about this matter.
Best regards,
Vincent

Perry

To understand buffers, see this video
https://www.khanacademy.org/science/ap-chemistry/buffers-titrations-solubility-equilibria-ap/buffer-solutions-tutorial-ap/v/buffer-system

1.  Yes. Generally pH in a shampoo shouldn't change much as long as water isn't evaporating. 
2.  Water evaporating, microbial contamination, oxidation of some feature ingredient could all affect pH.
3. You shouldn't need a buffer in a shampoo system but you might if the pH is drifting that much.

vhogiono

@Perry thanks for the link. I never use buffer before, and it seems its not necessary in my shampoo case, because i tested the yellow product pH is still the same around 5.0-5.5

I'm suspecting my color change is because of chlorine. I rinsed the empty bottle with 200ppm chlorine. Maybe I need to rinse it once again with distilled water to remove the residue of chlorine which I'm suspecting it as the color change cause.

PhilGeis

You do need to remove hypochlorite sanitizer - and with water of appropriate quality.
If you find you really do need a bauufer - this might help this http://clymer.altervista.org/buffers/cit.html

vhogiono

@PhilGeis thanks so much! this is really helpful calculator I will try to make this buffer and do some trial and error.