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Preservative for pH 9-10 liquid soap
What are my options for an alkaline based hand soap solution preservative?
Does a liquid hand Castille soap mixed with oils and glycerin need a preservative?Many thanks in advance for any help/advice given! -
29 Replies
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@Leo Usually bar soaps from saponification of either tallow or vegetable oils, are the ones that are basic (alkaline). If you have a liquid soap, you could actually have it at a pH closer to the skin (roughly around 4.5-5.5). If you want to stay at that pH range, isothiazolinones are very effective, same as formaldehyde-releasers (like DMDM hydantoin, Diazolidinyl urea, etc.), but that is if you’re ok with that type of preservatives.
I do believe your liquid Castille soap needs since you need quite some watter to haved in a liquid form.
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Will the acidification with for instance citric acid as a preservative affect the foam?
Are there any other preservatives that are “more natural” that can function at pH 9? -
If you lower the pH you will loose the bubbles.
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Here is an ingredient list. No preservative but an antioxidant. Look at the advisory information.😱
INGREDIENTS (INCI): Aqua, Potassium Cocoate (Saponified Coconut Oil*‡), Potassium Palm Kernelate (Saponified Palm Kernel Oil*‡), Potassium Olivate (Saponified Olive Oil*‡), Glycerin*, Potassium Hempseedate (Saponified Hemp Oil*), Simmondsia Chinensis (Jojoba seed oil*), Citric Acid, Tocopherol (Vitamin E), Helianthus Annuus Seed Oil (Sunflower Oil) *Certified Organic Ingredients/ ‡Certified Fair Trade Ingredients
Advisory information:
Vegetarians and Vegans. Don’t drink soap. If cap clogs, poke it clear, do not squeeze the bottle. Soap can clog and spurt with pump dispensers. Keep out of eyes. Flush eyes well with water for 15 minutes. Consult a physician if irritation persists.
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If the liquid soap has a pH 9 - 10, a preservative is unnecessary. Refer to ISO
29621 “Cosmetics — Microbiology — Guidelines for the risk assessment and identification of microbiologically low-risk products.”We have a GMP Certified production facility producing a lot of liquid soap, and export globally. These products are Notified with cosmetics authorities and all the necessary testing is done in our in-house labs and verified by external labs. -
@Leo If you have a liquid soap, you’d need to go very low on pH to prevent microbial growth, and as @Dr_Sara mentioned, it’ll impair foam and detergency, and it’d also increase the chance of instability (for instance, CAPB behaves as a cationic at low pH, which will interact with anionic surfactants forming a precipitate). It can be done, but you should be very careful with the ingredient selection…also, you’ll need a very good GMP system in place to guatantee that your water for instance is of very high quality, since low pH helps prevent microbial growth, but it won’t avoid your product being contamined from external sources.
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If the pH of the soap is around 9, do I need a preservative?
I see that a lot of these products have citric acid which affects foaming and performance? -
@Leo Citric acid in a liquid soap at a pH above 9 will be present as its salt (Citrate) rather than the acid form.
Regarding the need for a preservative, if your idea is not to include one, there are a couple of readings you might want to take a look at: https://onlinelibrary.wiley.com/doi/full/10.1111/j.1468-2494.2009.00492.x, https://makingskincare.com/preservatives/.
So, pH as a sole strategy could be tricky, since being at least at a pH of 10 for shrinking the risk of microbial growth (I’ve seen products being contaminated at pH around 9), can also mean that you might have free alkalinity in your product. Of course this is more sensitive for leave on products, but for individuals with reactive skin (not to mention if the product reaches your eyes) and under repetitive use, that might cause some problems.
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for true soap- a pH of 9 is good. I would add a preservative.
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glycerol monolaurate or monolaurin or propanediol or caprylhydroxamic acid to name a few. Any experience with these or other preservatives for pH near 9?
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Hi @Leo I have used phenoxyethanol in liquid soap.
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Does anyone have experience using Suttocide A (Sodium Hydroxymethylglycinate) as the preservative at high pH above 9-10?
How about Euxyl K940 ( INCI name: Phenoxyethanol, Benzyl Alcohol, Ethylhexylglycerin, Tocopherol)
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@Leo Suttocide A is a very powerful preservative (if you don’t mind that it’s a formaldehyde donor, of course), I believe you still need to add an antifungal.
But I believe Euxyl K940 might also lack of the same activity since Ethylhexylglycerin is not a powerful antifungal.
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What antifungals do you recommend and at what concentrations?
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@Leo Organic acids like Benzoic or Sorbic acid work well for this purpose (you can get them as their salts: Sodium benzoate or Potassium sorbate). You can start at 0.3%.
But if you don’t mind using a formaldehyde donor, then Glydant Plus or Liquid Germal Plus are very good broad spectrum preservatives. You can find a lot of literature about them.
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ketchito said:@Leo Organic acids like Benzoic or Sorbic acid work well for this purpose (you can get them as their salts: Sodium benzoate or Potassium sorbate). You can start at 0.3%.
But if you don’t mind using a formaldehyde donor, then Glydant Plus or Liquid Germal Plus are very good broad spectrum preservatives. You can find a lot of literature about them.
Organic acids would be useless in alkaline products, including liquid soap.
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mikethair said:If the liquid soap has a pH 9 - 10, a preservative is unnecessary. Refer to ISO29621 “Cosmetics — Microbiology — Guidelines for the risk assessment and identification of microbiologically low-risk products.”We have a GMP Certified production facility producing a lot of liquid soap, and export globally. These products are Notified with cosmetics authorities and all the necessary testing is done in our in-house labs and verified by external labs.
Liquid soaps can be contaminated. I’ve observed actual colonies of bacteria in/on amended bar soaps.
ISO 29621 claims pH >10 as cutoff for preservation, not 9-10. Recall please ISO’s are concensus decisions - good as a guideline but not absolute. Certainly one can have microbial contamination at >10.Please also recall that preservation is primary intended to protect the product in-use, not as delivered. In this, packaging is an important preservative element - maybe the most important for some products.
Have you in-use data for your application?
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@PhilGeis Sir-the packaging for the liquid soap (pH 10) is a plastic container with a foam pump.
Is a micro challenge recommended and definitive?
Which preservative(s) would you use?
In your experience, regarding a different product, have you heard of microbes contaminating a gel at pH 11?
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Leo said:
@PhilGeis Sir-the packaging for the liquid soap (pH 10) is a plastic container with a foam pump.Is a micro challenge recommended and definitive?
Which preservative(s) would you use?
In your experience, regarding a different product, have you heard of microbes contaminating a gel at pH 11?
Not sure I’d preserve that soap. Is this a cosmetic? How effective do you see the package as protection? Perhaps do some in-use exppsure.
ph !1 gel. Can you tell me smething about the product? At that pH - is it a cleanng product?
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Let me also add - as the pH becomes extreme, the classic PET becomes less useful - the product “passes” with or without preservaton even tho suscpetible to contamination. Be aware -the USP bugs are lab creatures that happily grow at ~ neutral pH where they’d lived since initial submission to ATCC up to 80+ years from isolation - on neutral pH media.
Also - the product contaminants as pH’s become extreme start to engage with extremophiles that won’t grow well (potentially won’t grow at all) on conventional media but will still deteriorate the product. Those bugs contaminating at extreme pH are less likely to be pathogenic but preservation at those pH’s is a real pain. -
@PhilGeis What plastic or other packaging materials hold up at pH 10-12 over time?
The product at pH 10 is a liquid soap and the product at pH 11 is an anti-wrinkle gel.
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I’m sure no packaging expert - but Clorox bleach (e.g. pH 12) - think it’s in HDPE. http://menda.descoindustries.com/PDF/ChemicalResistanceChart.pdf
Are you sure the anti-wrinkle is safe - esp. if used near eyes? -
Chlorox bleach is neutralized to a much lower pH than 12.
Household Bleach is usually at pH 11-13 depending on use.Common soaps have a pH of between 9-11 and have routine warnings to keep out of eyes and what to do if soap gets in your eyes.
The pH 11 gel will be used near the eye but it rapidly dries upon skin contact (within one minute). It may, in some, produce an intended mild irritation and mild redness of the skin that resolves after a few minutes. Once dried upon contact with skin, it cannot harm the eye.
Soap will do more harm to the eye since it is lathered and foamy and people tend to spread soap into their eyes during application. The key is to NOT get the gel in the eye during application with your fingers (which you have much more control than with soap).
Instructions: Apply to crows feet and under the eyes. Keep out of eyes. Do not apply to eyelids. Keep each eye closed until product is fully dried! Do not apply with other products.
Additional instructions will be provided if the gel gets in the eyes (rinse immediately with water and seek medical attention if eye irritation develops, etc.). Instructions will also be provided to address if irritation of skin is severe or persists.
One has to take risks if one wants to use a product that performs and provides effects on eye wrinkles!
If the product does not produce some form of harmful effect, it will not affect wrinkles….and will only be another marketing BS story….
The goal is to help 99% and expect that there will be a vocal 1% that will complain.
The media focus will always be on the vocal 1% and is the reason our society is becoming non-functional…like cosmetics in general.
Covid as a prime example! We are planning to vaccinate our entire population to preserve the 1% that are expected to die…. -
@Leo Clorox bleach uses Sodium hydroxide in its formula to stabilize hypochlorite ion, which is a powerful yet unstable oxidizer. The pH that @PhilGeis mentioned for Clorox bleach falls correctly within the pH range for this product.
I honestly wouldn’t apply such a high pH gel near the eyes. We need to consider that consumers commonly missuse products. And even if they use it correctly, that area of the skin is very thin and with less production of sebum, which not only doesn’t help skin buffer the pH change induced by the product, it also makes skin more prone to irritation. Alkaline soaps wil do more harm not only because of the pH, but because of the type of surfactants present in the formula, which are capable of denature proteins and induce an immune response.
There are many ingredients that can be more safely used to fight wrinkles in that area (there are few of them with proved efficacy), so it’d be an option to explore some of them.
Your example for Covid is missleading, but I believe is not worth discussing in this platform.
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