Low pH and colour changes

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Unisoap

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Hello all. I am new here and also new in soapmaking. I need some advice and help from fellow members. I was making some liquid handsoap and faced a few problems.
1. I noticed the colour of my handsoap turned yellow after a few days left in open container. I noticed some changes in the smell, too. I did a little experiment after that. I took two samples of my new batch of handsoap and put them into two different bottles. I added about 50% of tap water into the first sample and I added nothing to the second sample. I left both bottles without the caps and found that the first sample turned yellow after only a day. The second sample took two days before the colour turned slightly yellow. Any ideas that was happening on my handsoap? any solutions are greatly appreciated.
2. I tested the pH of my handsoap using a normal pH pen and the pH came out to be 4.3. From what I know, the pH of handsoap has to be around 8-10. (Please correct me if I am wrong). Should I use Potassium Hydroxide to increase the pH? or is it better to use Sodium Hydroxide?
Here is the formula for my liquid handsoap:
Sodium Lauryl Ether Sulfate 6%
Sodum Laury Sulfate 3%
NaCl (Table Salt) 5%
Cocamide Diethanolamine 0.5%
Lauryl Hydroxysultaine 0.5%
Nonylphenol Ethoxylate 0.1%
CDE Synamide 0.1%
EDTA-4Na 0.1%
Triclosan 0.2%
Fragrance 0.2%
Foodgrade Dye 0.1%
Water 84.2%

Thank you.
 

shunt2011

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Hello and Welcome! You're making a syndet liquid soap. Most here make Liquid soap with KOH so not sure you'll get much help.

Once of our more science geared members might have some ideas though and may pop in.
 
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Regarding your second point although many soaps have a high pH level (around 9-10) the recommended pH level for skin is much less (acidic) around 5.5, I recommend that you use an alkaline solution (either NaOH or KOH) and try to increase it a a bit more. You do however need to check effect on other ingredients such as preservatives and recommended pH level.

I wouldn't recommend using tap water for any of your skin care formulations since it could contain microbes and heave metals depending where you live. Make sure you always use distilled water and perform a trial if you still have a color change you might need to use a different chelating agent or increase the once you are already using since color change is usually related to uncontrolled pH changes.

Use distilled water before changing your formulation and measure pH at the begging and wait 24 hours and measure to check if you have any fluctuations in pH.

Regards,

Khalid
 
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