Vitamin C Serum - Ferulic Acid Crystallizes

Hi everybody!

I keep on trying to making a Vit. C serum that I can use and I have tried to simplify it as much as possible.

Last weekend I thought I had found the perfect/good enough for me recipe for a 30ml bottle:

Distilled Water                            20 grams

L- Ascorbic Acid                          4 grams

Glycerin                                       1%

Ferulic Acid                                 0,5%

Sodium Hyaluronate (RMW)          0,2%

1,3-Propanediol 2                       20%

Green Tee Extract                        1%

Xaromix or Geogard Ultra            1% or 2%

I have had problems dissolving the Geogard in the past, so this time I went for the Xaromix.

Everything seemed good, but after two days, small long filaments could be seen in the bottle. I had seen them before, so I knew that it was the Ferulic Acid. My question is, why? I mixed it with Propanediol and warmed it up to 70ºC and I did not use anything metallic.

Any ideas?

Thank you very much in advance,




  • I was wondering if nobody is replying because this is a silly question or because you need more information...
  • I am not familiar with ferulic acid. Does this happen with both of the preservatives?
    Design of anti-aging creams, gels, and serums; shampoos; and therapeutic cosmetics. In-house label and box design capability.
  • I suspect your problem is actually the Geogard Ultra and/or Xaromix as opposed to the Ferulic Acid.  Try switching to a liquid preservative ... 

    Add 6% Sodium Lactate to your water phase, heat it to 80C, and then add the Glycerin/Ferulic Acid slurry.  Add the Ascorbic Acid last.

    That will probably solve your problem.
    Chemist/Microbiologist formulating in the Organic & Naturals arena under ECOCert/Natural Products Assn/Whole Foods/National Organic Program guidelines focused skincare & haircare products. 

    Provides Formulation Development and Lab-Scale Contract Manufacturing Services.  See website for details

  • edited November 2017
    Did not use anything metallic?  What do you mean by that?

    I agree with Mark, you need something like sodium lactate, it'll keep the ferulic solubilized. What is your final pH btw? Sodium lactate is a buffer and raises the pH. Lotioncrafter also has a vitamin C/ferulic formula (they sell DIY vitamin C serum packages, very similar to Skinceuticals C/E Ferulic). They suggest triethanolamine without even heating the ferulic solution.
    A tip: I have a formula with ferulic acid (no vitamin C though), it also has 5% niacinamide and it doesn't even need sodium lactate: the high % of niacinamide keeps the ferulic solubilized. I got this tip from @johnb. The final pH of that serum is 4.7-4.9.

    About the Geogard 221 solubilization troubles: I only use it as a booster at 0,15-0,2% (mostly because of the awful smell and that's easy to mask with a fragrance at that %).
    What kind of microbiological test do you do to test the efficacy of your preservative system? Do you do challenge tests?
  • Ascorbic acid is too high;try reducing to half first ie from 4 parts to 2 parts.You can also replace it with sodium ascorbyl phosphate.Change preservative to germaben at 1%.
  • Hi Belassi! Yes, it happens with both preservatives.

    Hi MarkBroussard! The Xaromix is liquid but I will add the sodium lactate as indicated and add the ingredients in the suggested order.

    Hi Doreen81! I read somewhere that using metals when ferulic and/or L-ascorbic were involved in a formula could be an oxidizing fact. The first time that I tried making this serum I used a milk frother whisk to mix the ferulic acid with glycerin, and when I added the ascorbic acid, I immediately saw it crystalizing.
    With regard to the pH, mine was 3.5 when I last made it.

    I am afraid that I do not run any microbiological test. I make small batches and they last one month approximately. I do not sell this serum or anything like that, it is for personal use.

    Hi DRBOB@VERDIENT.BIZ, though I am going to keep on trying using the L-ascorbic acid, I have a formula with sap that I may try in the future.

    Thank you all very much for your help! I have taken very good note of everything that you have said and I will keep you updated with my progress!

  • As your pH is below 5 you could try to use MICROCARE SB as a preservative. It doesn't give many problems (or not to me until now).

    If the % of vit C is high remember we would probably have to add a citric (citric acid, sodium citrate) buffer  to stabilize the pH.

    About the ferulic acid...sorry I do not have experience with it.
  • Hi Maes! Thank you very much for your reply.

    At one point, I studied the possibility of using Microcare SB, problem is the recommended pH is 4-6 and my serum, in order to be effective, needs to be 3.5 or lower.

    On a different note, I do not why, but when I saw you your profile photo I though: "That girl looks Spanish!".

    Greetings from Málaga! ;)
  • edited November 2017
    It's ok to go below pH4 with Microcare SB (sodium benzoate, potassium sorbate), actually it's even better. These are the sodium and potassium salts of benzoic and sorbic acid and they need an acidic environment to convert to their acid form. At pH>5 they are no longer active. pH 3.5 is great.
    They are unsaturated fatty acids, so you'll need an anti-oxidant like BHT.
    It also isn't broad spectrum, you'll need something against bacteria too.

    FYI there have been worries about benzene forming when combining sodium benzoate/benzoic acid with ascorbic acid, but it's ok to use these together. Concentrations are low enough not having to worry about it, benzene forming also happens naturally. (Cranberries for example contain both benzoic acid and vitamin C).
    Just like formaldehyde releasers, concentrations in cosmetics are very low (comparable to formaldehyde levels found naturally in vegetables and fruits e.g. pears and grapes).
  • further to @Doreen81's comments about benzene formation, I might also add this reaction only happens in the presence of iron, because the iron acts as a catalyst: as a reducing agent, ascorbic acid on its own is nowhere near powerful enough to reduce benzoic acid to benzene (if it were, it would be much more hazardous, both to human health and in general)

    if you use deionised water and a chelator, the concentration of iron in the product will be somewhere between undetectable and nothing at all
    UK based formulation chemist. Strongest subjects: hair styling, hair bleaches, hair dyes (oxidative and non-oxidative) I know some stuff about: EU regulations, emulsions (O/W and W/O), toothpaste, mouthwash, shampoos, other toiletries
  • edited November 2017
    I forgot about the organic acids becoming less water soluble in their acidic form, sorry! Maybe pH 3.5 is indeed too low as they might give precipitation and become useless. Parabens would be a great choice for you as they are effective, safe and less pH sensitive.

    Thank you for adding the information about iron as catalyst in the reaction. It also makes al lot of sense why they did worry about it in the softdrink industry as 1. the benzene will be ingested and 2. I reckon they don't use demineralized water for soda, so catalyst(s) are present. Do all transition metals act as reducing agents in this reaction, or is it only iron?
  • Is acid ascorbic stable in that formulation?
  • @em88
    No it isn't stable. Intentions aren't for selling, it will be used within a month.
  • Now it makes more sense :) 
    Thank you
  • @em88
    You're very welcome. :-) 
  • @Doreen81 iron and copper are the most likely culprits; other catalytically active transition metals (manganese, platinum, palladium etc.) are typically present at such low levels, assuming they're present at all, that they have little if any effect
    UK based formulation chemist. Strongest subjects: hair styling, hair bleaches, hair dyes (oxidative and non-oxidative) I know some stuff about: EU regulations, emulsions (O/W and W/O), toothpaste, mouthwash, shampoos, other toiletries
  • @Bill_Toge
    Ok, thanks for the information!
  • edited December 2017
    Have you made progression so far?

    Re: organic acids and pH.
    Today I made a 2% BHA toner (benchmark Paula's Choice 2% BHA liquid pH 3.2-3.8). PC doesn't use additional preservatives in this formula besides the polyols and salicylic acid, but I wanted to incorporate at least something against yeast/mold, so I tried benzoic and sorbic acid on a selected part of the batch.
    The native pH was well below 3, I raised it with NaOH to 3.76. This seems to be too acidic for the acids (except for SA). As soon as I added the acids to the crystal clear solution, it started to precipitate and the insoluble matter floated on top of te liquid. So even a pH of 3.76 is too acidic for them. I thought I'll let you know, maybe it's helpful for you or someone else on here.
  • edited January 2018
    Hi everybody,

    I like to keep you updated with my progress (it is also a way to show you my gratitude for all your help).

    I made a new batch 3 weeks ago and it turned out perfect (at least, from my point of view).

    This is the new recipe:

    Distilled Water                     20g
    L-Ascorbic Acid                   4g
    Glycerin                               1%
    Ferulic Acid                          0,5%
    Sodium Hyaluronate (RMW)  0,2%
    1,3-Propanediol                   20%
    Green Tee Extract                 1%
    Sodium Lactate                     6%
    Citric acid                             q.s.
    Xaromix                                1%

    I added sodium lactate as MarkBroussard suggested, added the L-Ascorbic Acid last and used xaromix as opposed to Geogard Ultra (dissolving it properly is almost impossible for me).

    I believe that, due to addition of the sodium lactate, my final pH was around 4, so I decided adding a little bit of citric acid. I was hesitant at first as I did not know if the final product would be too harsh on my skin, but after giving it some thought and do some research, I went for it.

    The serum is really nice, up until today there is no visible oxidation and the “filaments” are now history.

    In order to make things a little bit more complicated I was thinking of adding disodium EDTA next time as a chelator. Any thoughts?

    Edit: Formatting
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