Product darkening - Chemists Corner

Formulating

Product darkening

Posted by Sethr on September 22, 2015 at 4:19 pm

Hi, I am having a problem with my face pads darkening after abou two weeks. I have done quite a lot of research, and even changed some of the ingredients. I used to use aloe juice, but switched it to a high quality organic freeze dried powder. I look into each ingredient, and I saw one article about how the vitamin c could be the cause. The formula ph is 3.5. Here is the ingredient list, Organic Whole Leaf Aloe Barbadenis (Organic Aloe), Organic Salix Alba Extract (Willow Bark), Organic Witch Hazel, Organic Orange Blossom Water, Vitamin C (L-Ascorbic Acid), Glycolic Acid, Vegan Hyaluronic Acid, Non-Synthetic Vitamin E (D-Alpha-Tocopherol).

If the vitamin c is the cause, do you think replacing it with Kakadu plum extract would be a good idea? I have read that it is very high in vitamin c. I also looked into using sodium ascorbyl phosphate, but it has an optimal ph of 5-6, so I’m not sure if it will cause darkening to occur as well.

Thank you for any help! I really appreciate it!

Kirk replied 9 years, 3 months ago 7 Members · 8 Replies
8 Replies

AuroraBorealis

Member
September 22, 2015 at 5:15 pm

It is vitamin C. And Kakadu extract darkens too. Everything with vitamin C changes color unless it’s sufficiently protected. Even then, you can only delay oxidation, not prevent or stop it.
Sethr

Member
September 22, 2015 at 5:17 pm

Thank you! Do you have any suggestions as a preservative for the vitamin c?
Vin

Member
September 28, 2015 at 7:59 am

You’ll need to prepare a buffer system (sodium citrate+citric acid) to stabilize the vitamin C. You can request from you supplier.
Sethr

Member
October 21, 2015 at 3:03 pm

I wanted to give an update on the formula. I was able to get the new formulation made today, which uses much less vitamin c, and already it is looking much clearer than any previous version. I will update in a week to note if any yellowing or darkening occurs. Thank you all for the help!
OldPerry

Professional Chemist / Formulator
October 21, 2015 at 3:22 pm

Thanks for the follow-up
billichemist

Member
October 25, 2015 at 9:39 pm

@Vin How exactly does one use a buffer to stabilize it? do we just add an equal amount of sodium citrat + citric acid buffer as ascorbic acid to the final forumlation? or pre dissolve the ascorbic acid into the buffer? sorry this is such a basic question! i feel like i should know this but i dont!
braveheart

Member
December 10, 2015 at 1:11 am

@billichemist….. It depends on your formulation, 0.5% - 5% of Sodium citrate is enough.
Kirk

Member
December 10, 2015 at 2:20 am

or you can use the Henderson-Hasselbach Equation to compute the amount of citric acid and sodium citrate that you need to use at a specific pH.