Impossible preservative challenge- need help!

I am new here and originally found this forum because of a challenge I'm grappling with. 
I'm nervous to admit that I'm not working on a cosmetic formula... I am working on a artist paint product. But it is to be non-toxic, and totally safe for people to get on their skin or even in their mouth. So I've been looking into the cosmetic world a lot while working on this.

That said, I'm struggling with my preservatives. What "non-toxic" has come to mean in this project is "non-toxic" in the eyes of the market. This is extremely limiting for preservatives in particular. Not only that, but my formula has a saponified wax base, so I am unable to use an acid preservative because it breaks the emulsion.

So right now by preservative restrictions are:
-no parabens
-no formaldehyde releasers
-nothing that contains VOCS (phenozyethanol is one)
-no isothiazolines 
-no acids

And then it obviously also has to work well. 
Do you have any ideas?  I've been looking into sodium pyrithione and maybe something with silver (??), but my constraints are starting to feel ridiculous.
If you have any suggestions, I'd love to hear them, but I'd also love to hear if you think I'm being too strict. The whole point of my product is that people don't have to worry about anything in it, so I was trying not to include things that the general public has concerns about (although some quacks have concerns about everything, so I'm trying to ignore those). 

Please let me know your thoughts, and thanks for welcoming me to your forum. 


  • PharmaPharma Member, Pharmacist
    What about alcohol (upss, a VOC ;( ), glycols and glycerine? That's the only food grade 'preservatives' I can imagine work at higher pH and don't sound too scary (okay, alcohol makes you drunk and simpletons believe that all glycols are antifreez). Or omit water in your product.
    Silver can work but not at higher pH and not in most formulations. Pyrithione is not safe to eat like most of the others I can think of.
    Apart from that: most preservatives requires low pH, sound like super scary baddies, are non-edible, have been banned years ago, and/or are utterly useless... may we see the whole composition?
  • amoricalamorical Member
    edited March 2020
    Thanks for your thoughts, Pharma. 

    Yes, I just started looking at Lincoln Products, specifically Linatural Ultra-3 , Linatural MBS-8 , and Lincoserve PA-2. Does anyone have any experience with these products? In Phenethyl Alchohol (which is in all of them) a voc?

    Ingredients in my formula so far: Water, Liquid Soap Base (Water, Olive Oil, Glycerin, Potassium Hydroxide), Beeswax, Pigment, Glycerin, Gum Arabic

    I'm working on adding in Sodium Phytate.

    And I'm definitely not suggesting that they eat it! Just that if a little gets in their mouth/lips they don't have to call poison control or anything. 

  • AgateAgate Member
    edited March 2020
    Maybe it's a stupid question, but if you're basing this on soap, couldn't it be formulated to be "self-preserving" via a high pH?
  • PharmaPharma Member, Pharmacist
    Phenethyl alcohol is slightly volatile and preserves head space (that's the air up in the bottle/jar). It behaves like a perfume, so to speak.
    How much water and how much glycerine does it contain? There's the chance that you could use propylene glycol instead.
    Else, there's a bunch of other more or less natural/green/alternative preservative mixtures out there but yes, many of the pH independent ones contain phenethyl alcohol or else phenylpropanol (a similar compound). They make the blend way safer in terms of microbes, allow for a lower % of the other preservatives in the blend (lowers cost and 'stickiness' of glycols and has also lesser impact on things like viscosity), and are okay if the product isn't eaten spoonwise.
    Phytate is not a preservative but a chelate which boosts antimicrobial activity of many preservatives and helps against olive oil going rancid. It's a good and safe choice. Phytic acid is the main storage form of phosphate in cereal grains, nuts, beans, and many more seeds -> you eat phytates every day. Usually not the healthiest food constituent for humans but you could actually eat it spoonwise :smiley: .
  • I thought about it being self preserving with a high ph, but I wasn't sure if having the ph that high itself would be irritating on the skin. I just don't know enough about that to feel comfortable relying on it. I could be convinced otherwise though, if someone has experience with it... 

    Rats about the phenethyl alcohol, I was feeling like I could go with Linatural Ultra-3. It's weird, I can't find anything about it being a VOC anywhere. In terms of spoon-wise, isn't it commonly used as a food flavoring? 
    I was trying to avoid propylene glycol as it is derived from petroleum (another thing I'm trying to not have)

    I honestly don't care about it being "natural" or "green" (the linatural was just coincidence, hehe), as long as it is as least-toxic as it can be while still be an effective preservative (and not derived from petroleum!). Is phenylpropanol also a voc? 

    Re: Phytate. Yes, I know, I was including it not to say that I had my preservative figured out, but that I was adding a chelator (just haven't gotten around to working it in yet) 

    Thanks so much for your help. 
  • What about Lincoserve WpH-LO or Lincoserve WpH-LO Plus

    Pentylene glycol, propanediol, caprylyl glycol, ethylhexylglycerin

    And "Plus" contains all that chlorophenesin 

    Any experience or thoughts about them? 

    Side note:
    Linatural Ultra-3 contains 5-15% phenethyl alchohol, so if you added it at 1.3%, at most you have .195% VOC content in your paint, which can still count for claims of "zero-voc" paints (you can have up to 5g per liter). Feels like lying to me though...
  • PerryPerry Administrator, Professional Chemist
    What is your standard of what makes something "toxic"?
  • amoricalamorical Member
    edited March 2020
    As I say in my first post, what "toxic" has come to mean in this product is in relation to the eyes of the market, with the exception of widely outrageous quacks making ridiculous claims. So the things I've listed in my first post (vocs, formaldehyde releasers, isothiazolines, parabens) which are seen by the general public as harmful (even if they aren't in the tiny qualities they're generally used in) I have been trying to avoid.
    If you think that I can claim to be "non-toxic" while ignoring the concerns many people have about those ingredients I would really love to hear your reasoning. 
  • PerryPerry Administrator, Professional Chemist
    Then I'm a bit confused.  What do you mean by this? 
    "as long as it is as least-toxic as it can be while still be an effective preservative"
    If there is a "least toxic" that means there must be some scale of toxicity, ergo a "most toxic."  So, if there is a least and a most, what is your scale? How is toxicity measured?

    Is methylparaben more or less toxic than a formaldehyde donor? 

    Is it just an "unpopularity" contest? If so, how do you measure that? How are you measuring consumer familiarity?

    If you want to say in the eyes of the market, then who are you talking about? The vast majority of products bought by consumers have parabens, formaldehyde donors, and isothiazolinones in them.  Dove, Fructis, Olay, Pantene, L'Oreal, etc.  They all use them. As far as the market is concerned (at least when it comes to what most people buy) those things aren't seen as toxic. The general public doesn't even know what they are or care. If you read the Internet or NGO websites you might get that impression but if you look at the market and what people buy, that's a different story.

    You can certainly claim "non toxic" and include those preservatives.  Even the terrible, misleading EWG rates methylparaben as a 3 on their scale of toxicity 

    If it's an ingredient that might work but consumers have never heard of, maybe iodopropynyl butylcarbamate or Chlorphenesin

  • These are excellent points, thanks for your thoughts. 

    I don't have a scale, rather I am just working off the premise that I want my customers to not have worry about what is in the product. So I was trying to avoid the big "scary" things that get a bad rap. Many architectural paint brands that advertise as "non-toxic" or "eco" also advertise as not containing formaldehyde donors, parabens, etc, and I think there is a corner of the market that with a big focus on the "non-toxic" trend of "natural", "eco-friendly", "green" etc etc etc. 
    Re: "as long as it is as least-toxic as it can be while still be an effective preservative"
    I guess I mean, maybe I do need to use the things I'd rather not to have an effective preservative system, but I would rather try to avoid it. But most important is that it's not actually going to irritate/sensitize/harm the consumer.

    Sorry for not having a more concrete answer. Still trying to figure it out. 
  • PerryPerry Administrator, Professional Chemist
    I guess it comes down to what kind of marketer / product producer you want to be.

    Is consumer safety your number 1 priority? If this the case then you should drop all of your restrictions as to which preservative you'll choose and then pick the one that is the most effective, reliable, safety tested, and researched. There are literally multiple decades of safe & effective use of parabens, formaldehyde donors, and other standard preservatives. If safety is your main concern, use what has been proven time after time to be effective.

    However, if actual consumer safety is of secondary importance to your marketing position and the "impression" of safety is more important, then by all means use a less proven, less safety tested alternatives to the standard preservatives. 

    Try things like ...
    SymOcide C
    Lincocide™ C
    Sharon™ Biomix Free 

    or any of the other new, unproven-effective?-but-consumers-are-not-yet-afraid-of alternatives. They might work in your system. 

    It's riskier and more likely that you're producing an unsafe product, but you won't run afoul of misinformed bloggers, consumers, reporters or NGOs and your marketing position will be secure.

    Your illusion of safety may even work in the marketplace for some time. Fear marketing is quite effective. Although it could also lead to harming consumers and brand damaging recalls down the line but you will be able to better market the impression of safety.

    It's really up to you to decide what kind of marketer you want to be.
  • amoricalamorical Member
    edited April 2020
    I hear what you are saying, and it makes sense. 
    And I also wonder- can you have both? Avoid the things that people are afraid of and still use a researched and reliable product? 
    If you could find the best of both worlds, why not try?
  • And even if I was to use one of those- which would use suggest for an alkaline formula that will break with an acid, that contains pigments? I was thinking BIT + NaPT (Proxel LS), but even on here people who seem to know what they're talking about shoot down isothiazolinones. 

    Consumer safety is my priority. The my whole premise of my product is "no worries". So if I use a product that freaks people out, do I just not disclose it? I would rather be able to be transparent with my customers.

  • PharmaPharma Member, Pharmacist
    edited April 2020
    You have to be transparent and have to declare what you use!

    Thiazolidinones are strong preservatives and widely used (most pain and many cleaning products for laundry/cars/dishes contain it -> often undeclared because of different regulatory guidelines). I really don't like them (bad for the environment and rather poor investigations regarding overall safety etc.).

    Don't use a ferment or a herbal extract based preservative. These are likely to break down and fail at elevated pH.
  • PerryPerry Administrator, Professional Chemist
    Proxel LS looks like it's an industrial preservative and not one that we use in the cosmetics industry.

    Without knowing all the ingredients in your formula, it's hard to give any specific preservative recommendations. A blend of parabens and formaldehyde donors is the most versatile & effective and that is probably what you should use if safety is your concern. Isothiazolinones are not as bad as some people believe but they are meant only to be used for rinse off products in cosmetics.
    can you have both? Avoid the things that people are afraid of and still use a researched and reliable product?  
    No. You can't have both. Unfortunately, all of the preservatives that have the most safety & efficacy research behind them plus decades of safe use have been vilified to the extent that some consumers are afraid of them. You've made an entire list of all the things you want to avoid. Well, those are the things that work. 

    Any alternative you pick will be a newer material that does not have as much safety validation research behind it. It takes years to collect this information & it can only be proven out over time and use. 

    If there was some readily available, effective preservatives that consumers weren't worried about, everyone would be using it. 
  • Okay. You have me swayed. I will continue to do my research and be stunned by the fact that there is nothing proven to be wrong with methylparaben.  ;)

    In the meantime, can you tell me your opinion of a system with pentylene glycol, 1,3- propanediol, caprylyl glycol, ethylhexylglycerin, and chlorophenesin?
  • PerryPerry Administrator, Professional Chemist
    Start here.

    Then here.

    These are the opinions independent scientists, toxicologists who have actually done research. 

    The system you describe might work. Ethylhexylglycerin can cause stinging but it may not be a problem. 
  • amoricalamorical Member
    edited April 2020
    Thank you for your continued help, Perry and Pharma. I appreciate it and your patience.

    But looking into it parabens don't even work well in formulations with a ph of 8 or higher (mine is 9-10). 
    Also-- I did list my ingredients above, Perry.

    The list you provided of:
    SymOcide C
    Lincocide™ C
    Sharon™ Biomix Free 

    None of these make any sense for my product. The first isn't soluble in water, the second doesn't work in a high ph range, and the last two don't seem like they'd work in general.

    I'm not a chemist but I'm not a fool either, and I'm genuinely trying to make the right decision. I get that you don't like when people are needlessly (and maybe stupidly) biased against things, and I hear your point loud and clear, but I don't want or need suggestions for things that aren't applicable to my formulation.

  • PerryPerry Administrator, Professional Chemist
    @amorical - I apologize. I did not see your ingredient list or your listed pH. I read your initial comment when I first posted my comment and then didn't go back and see your interactions with all other commenters. This is why when anyone posts a question, they are encouraged to put as much detail as possible in the first comment.  But I digress...

    If you're pH is 10 then Phenoxyethanol is an option. 
    Methylisothiazolinones work up the pH 9 so maybe you could use them.
    Iodopropynyl butylcarbamate could work too but may not be compatible with your system.
    Sodium Hydroxymethylglycinate works up to pH 12 so that's another option as is Quaternium 15.
    Ethylhexylglycerin is stable up to high pHs but it's only a preservative booster.

    Of course, none of these meet your initial requirements except maybe the butylcarbamate.

    Hope that helps.
  • PharmaPharma Member, Pharmacist
    edited April 2020
    @amorical There's no point in filling anything out in the form @Perry posted because the only thing they have to offer for your high pH product is DMDM Hydantoin & Iodopropynyl Butylcarbamate
    pH 10 is indeed a problem for several synthetic and natural preservatives containing for example an ester function such as parabens or GMCY. Getting the pH down to 9 would allow for pretty much any you like (except acids which require a way lower pH). On the other hand, 10 is also a pH at which you won't have to care about yeast and where only a few bacteria can grow; several different fungi won't mind, though, and they might grow mainly on the surface, you hence need head space protection -> these compounds are per definition VOCs (though might not pose any restrictions due to low usage %). If you manage to lower water activity, you'll be +/- left with just fungi to worry about. In other words, you won't need additives which target bacteria.
    How much water and glycerol do you use?
  • Thank you both. 

    I am actually not totally sure if it is 9 or 10 as I'm having trouble getting a solid reading. The first time I tried I did it with the pigment in it (bad idea), not to mention the emulsion broke when I diluted it so the wax was floating on the top. I will try again with just the base. But I am pretty sure it is 9 or 10 because of the liquid soap. I could probably adjust to either without messing up the emulsion (I think). 

    What options would open up to me at 9? I feel like most things I see, if they are to be used at a ph above 6 or 7 they often are very broad, like up to 11, so it didn't seemed like it mattered. 
  • PharmaPharma Member, Pharmacist
    amorical said:
    ...not to mention the emulsion broke when I diluted it so the wax was floating on the top... 
    For pH readings you don't have to bother with emulsion stability and if the wax floats on top, just remove some if it's in your way.
  • Okay, good to know. I will test again. 

    My water percentage changes with the pigment being used, but in the base it is 20.9%. At the highest with pigment it is 35.8%. Glycerin is right now 2.2%. Recipe is still in the works though (obviously). 

  • PharmaPharma Member, Pharmacist
    Hmmm... if you wanted to maintain hydration, you could switch glycerol for 1,2-hexanediol alongside some less traditional preservative.
  • amoricalamorical Member
    edited April 2020
    Okay, so I tested ph again and came out with what I suspected, around 9.8.

    I tried a blend of 2% BIT and 8% sodium pyrithione at 1% of the formula. I put a dab of the result on my face and it stung after a while. Not that this is face paint but I don't want it to sting if it happens. 
    Hmmm... if you wanted to maintain hydration, you could switch glycerol for 1,2-hexanediol alongside some less traditional preservative.
    I'm confused. How would this help me? Is something wrong with using the glycerol? I would be okay lowering water activity, but I'm not totally sure how...

    I have not been able to get samples of the pentylene glycol, propanediol, caprylyl glycol, ethylhexylglycerin and chlorophenesin blend because of covid, but I'm still curious as to your thoughts on it. Would it work or is it just a blend of boosters?

  • PharmaPharma Member, Pharmacist
    edited April 2020
    Unfortunately, the amount of glycerol in your product is way too low to noticeably affect water activity. Had you told me it contains 20% or so...
    There is nothing wrong with glycerol just that switching it for hexanediol or pentylene glycol would give you a marked increase regarding microbial stability whilst maintaining more or less the same effect of glycerol. This way, chances are higher that an alternative preservative will work or, at least, that the amount of traditional preservatives can be kept low.

    I have zero experience with your blend. Combining a booster with cayprylyl glycol or the like and an acidic or a phenolic preservative (traditional or alternative) is state of the art and makes total sense. It seems to me a bit superfluous to combine an old antimicrobial (chlorphenesin) with caprylyl glycol (antimicrobial/booster) and 3 ingredients which mostly act as boosters. There is not much logic behind that, if you ask me.
    Astonishingly, chlorphenesin is often added to alternative preservation systems (it's also used widely in technical products and soaps, mostly in the USA). My speculation is that it's added because first, other alternative/natural preservatives didn't work, second, it also acts as cosmetic biocide (killing microbes on skin = deodorising and anti-comedogenic), and third, though it's on the 'ugly' list, nobody cares about it. In my opinion, whoever adds chlorphenesin to a modern product earns a beating for being lazy :smile: . Chlorphenesin should either be replaced with a 'real' but environmental friendly traditional preservative or one should go the extra mile finding a true alternative system combined with for example triethyl citrate and/or sodium caproyl/lauroyl lactylate for the 'biocide effect'.
  • Bill_TogeBill_Toge Member, Professional Chemist
    for what it's worth, sodium pyrithione is VERY toxic; the reason zinc pyrithione is used in its place is because it's much less soluble in water, hence less bioavailable
    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.
  • czkldczkld Member
    Aren't isothiazolinones banned for use in leave-on applications regardless?
  • PharmaPharma Member, Pharmacist
    Sodium pyrithione and benzisothiazolinone are usually used for in-can preservation of paint...
    I couldn't find much useful about SPT. Seems as if it's still under investigation whether or not it should be a regulated substance for paint preservation. Given the better water solubility, it might be safer on skin than ZPT which is regulated and only allowed for rinse-off and hair products.
    Same goes for BIT. The proposed maximal concentration is 100 ppm (or 0.01%).
    From what I could find, both are neither in any negative nor any positive list regarding cosmetic ingredients.
    Personally, I wouldn't use either of the two.
  • When I have tried to increase glycerin it results in a slimy stickiness that is not super great. I can try again though. I like what I'm reading about 1,2-hexanediol, except that it is volatile.

    Thank you to everyone for your thoughts and help. I am not attached to the BIT or SPT, just trying to problem solve and feeling like I'm running out of options. 

    I am thinking of hiring a formulator to help figure it out, unless anyone has any fabulous solutions. What works at 9.8 ph, that doesn't hurt peoples skin, and doesn't contain vocs? Anything? 
  • PharmaPharma Member, Pharmacist
    edited April 2020
    amorical said:
    ...I like what I'm reading about 1,2-hexanediol, except that it is volatile.
    ...I am not attached to the BIT or SPT, just trying to problem solve and feeling like I'm running out of options. 

    I am thinking of hiring a formulator to help figure it out, unless anyone has any fabulous solutions. What works at 9.8 ph, that doesn't hurt peoples skin, and doesn't contain vocs? Anything? 
    Only if your AC is broken and your flat heated up to over 200°C ;) .
    Seriously, it's not a VOC and boils at a temperature where several other cosmetic ingredients have already self-ignited or charred. If you're still in doubt, go with caprylyl glycol, a closely related antimicrobial diol with a 20°C higher boiling point (i.e. ~240°C). But again, whatever boils above 100°C and hasn't a high vapour pressure is far from being volatile or considered a VOC. On the other hand, essential oils though having equally high boiling points as hexanediol still evaporate at room temperature due to high vapour pressure and therefore are VOCs.
    Why don't you want phenoxyethanol? It boils at 250°C and, although it has a vapour pressure high enough to ensure head space preservation, it is not a VOC plus it is stable at pH 10.
    BIT on the other hand is an isothiazolinone and IIRC, you don't want that in your product, do you?
  • Phenoxyethanol isn't a voc??? I definitely thought it was and definitely read somewhere that it was! I can't find where I read that though... Unfortunately I don't know enough chemistry to know if something is a VOC or not other than by google research.   :s 
    That's totally a game changer! 
    So I could just use phenoxyethanol and caprylyl glycol or ethylhexylglycerin? What pairing would you recommend?
    This is so exciting!! I crossed it off my list eons ago! Thank you so much. 

    Good to know about the 1,2- hexanediol! I will look into that more too. Maybe it will have less stickiness factor? Talking to people who actually know what they're talking about is equal to hours of research to me.
  • Could you explain why there is so much contradictory information on whether phenoxyethanol is volatile or not? All the little mentions I find about it say differing things? Not doubting you, just trying to understand.
  • Are formaldehyde donors VOCs? I'm just doubting everything now.
  • PerryPerry Administrator, Professional Chemist
    edited April 2020
    I do believe Phenoxyethanol is a VOC.  At least according to the EPA.

    No, formaldehyde donors are not VOCs, although formaldehyde is.
    Here is what the California Air Resources Board lists as VOCs.

    Whether something is a VOC or not is a regulatory question. The answers don't always make scientific sense.

  • PharmaPharma Member, Pharmacist
    edited April 2020
    Mea culpa!
    Sorry, my brain must have had the hickups.... it's not boiling point above 100°C but 240-260°C.
    So, I did some research: Turns out that the limit of 240°C is only here in Switzerland where phenoxyethanol is indeed not regarded as VOC. In the US it's 250°C and/or photochemical reactions (likely to happen) and in the EU 260°C. Vapour pressure for all is well above phenoxyethanol and hence, boiling point should theoretically be irrelevant but alas, as @Perry said, there is not much rational basis behind what's considered a VOC and what not and therefore huge differences exist between different countries/regulatory organs.
    Phenoxyethanol has a boiling point of 247°C. Fu#*@ ;( ;(
  • HalimHalim Member
    I have some experiance on paint
    you can solve this problem with 2 way
    1- If possible you must keep pH between 10-10.5 this is very troublesome
    ın my test ı cant keep pH 
    2 - If your system is opauqe you can use Omya Smart Zero
    ıts powder form and dont includes Voc
    NaPy-ZnPy dry film preservatives They are not suitable for in can protection and with
    2 phenoxy ethanol you will have Voc

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