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SOS - Thickening Sodium Lauryl Sulfoacetate (Shampoo)
I didn’t want to ask for help, but if I have to make another test sample I’m going to lose my mind. Hopefully you guys know something I don’t.
My goal is to have my cake and eat it too. I want a texturally perfect product, with enhanced health benefits and a very weak cleansing property all while using minimal, and only singular chemicals that can be tested with QNMR.
I’ve decided that Sodium Lauryl Sulfoacetate is my desired surfactant. But it’s too effective at removing oils, so I am limiting its exposure to 2-3%. Before you say anything, I am not interested in “coca”midopropyl betaine, nor am I interested in guar gum, nor xanthan gum.
I would like to superficially enhance the foam, while increasing the viscosity to an appropriate, syrupy consistency. PEG-150 Distearate just made it opalescent, and did nothing to viscosity. Cetearyl alcohol and cetyl alcohol were not brought into solution by the SLSa. Hydroxypropylmethycellulose was very close at 1.2% to being feasible, but it completely eliminated bubbles so I had to scrap it entirely.
So I’ve begun experimenting with Carboxymethylcellulose Sodium, and it almost worked at 1.3%. But, and perhaps due to its anionic nature, it left my hair feeling very dry, meaning my formula isn’t ready. And
I tried salt thickening with Magnesium Chloride recently, but had to call it off after incrementally adding over 2% did nothing. I figured it would work, because of the anionic property of SLSa. Using a Magnesium salt appealed to me, because of the health benefits of Magnesium, but I’m beginning to wonder if using a divalent salt was wrong and I should try again using Sodium Chloride.
I will receive Citric Acid tomorrow, I was attracted to vitamin C for this role due to multipurpose for health until I learned the tragic reality of its instability and its salts being of much greater PH. Not sure if a reduced PH is necessary to invoke salt thickening, but that gives me hope if so.
I read about β-casein being able to create micelles, so I’m considering sodium caseinate despite it straying from my one chemical policy. The problem with that is of course the big question mark around it degrading in storage, sterilization and purity. Ordering a sample would also require a purchase from Europe, and I’m sick of all the delays with this project.
One other card I have up my sleeve still is hydroxyethyl cellulose. I’m going to prepare another sample using that tonight, and just hope it’s enough on its own. Also curious about refattening and if that actually works when you’re cleansing, or if you simply have to bind the hair with polymers (which I’d like to avoid). Wondering if 0.5% Caprylic Acid would actually do anything, or just cause separation in the solution.
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16 Replies
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Oh, and I wasn’t able to find a sample of Oleamide DEA for sale, so I’d have to wait for my suppliers to send it from abroad which is a huge pain.
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Please don’t get me wrong, but just reading your post, I don’t know if you’re willing to accept evidence-based information. Just as a side note, most Cocamidopropyl betaine use coconut or palm oil as one of the starting materials, probable same as the sulfoacetate you’re using.
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I’m not trying to argue with you on this, but for educational purposes you should know that there are a plethora of fatty acids in coconut or palm, by merely reacting crude oil to form surfactants you aren’t forming a singular chemical, but multiple. Lauric acid is a singular fatty acid. By extension, Sodium Lauryl Sulfoacetate has a predictable chemical structure. This means it can achieve high levels of purity. Cocamidopropyl betaine cannot be tested with QNMR. Most surfactants, especially these “naturalist” ones, while practical, are highly contaminated or inherently mixed. A unique goal of my product is to narrow down on the absolute best singular chemicals, and allow no impurities. I will be purity testing each chemical to derive a percentage. This has never been done before, and it really shows the disparity between pharmaceuticals and cosmetics. Just because you aren’t swallowing it, doesn’t mean it isn’t absorbing through your skin and into your bloodstream transdermally.
I’ve already purity tested multiple sources of Lauryl Glucoside and found they are highly contaminated. I’ve inquired on a variety of other surfactants and most score below 80% purity. The cleaning industry is quite dirty.
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Good luck on your quest, I think you’ll need it.
1. Impurities do not inherently mean a product is poor performing or unsafe- can you elaborate if there are specific impurities you are worried about? You may also want to consider the reality of producing at scale- if you are single sourced on all your ingredients because your acceptance criteria is unnecessarily strict, then you are at the mercy of your supplier(s) in terms of pricing, availability, and lead time.
2. Transdermal absorption can happen with cosmetics, but can you point to why you think it might occur in a system you are designing to wash off with no stated deposition mechanism? At worst I think you might get some damage of skin proteins because you are planning to use a single anionic surfactant when there is a significant body of literature showing mixed micelles using multiple surfactants are generally milder to skin (less damaging to the barrier, and I think this would indirectly prevent some of that absorption you are so worried about).
3. can you explain why xanthan and guar are off the table but CMC (another anionic polymer) was acceptable for you to test?
I’m confused about why you feel your goal will lead to a better cosmetic product and I’m inclined to agree with ketchito- you may not be ready to consider options that have merit if you just don’t like them.
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1. I recognize that you can use a questionable mix of ingredients and still get practical results. But my approach is clinical precision: I want to know what chemicals are in my product, how much of them, and what is occurring during the process. I’m already a business owner in the chemical industry. And I have great connections, though it is kind of you to offer that advice regardless. It’s true that during the beginning I did get screwed, until I knew who to trust.
2. My product actually aims to deliver multiple topically-active drugs to the scalp. I am by no means aiming to discourage skin penetration. However, I am indeed concerned about the wide margin of error that may occur with impure products, and how that opens the floodgates to contamination of other dangerous ingredients. While the product is wash off, customers will be instructed to work it in and to leave it on for as long as they can until washing it out/ until their shower is over. My attempt to make it “gentle”, is by reducing the concentration of the surfactant, while increasing foaming with non-surfactants.
3. Xanthan, and Guar gum both give a snotty consistency that is bulbous and texturally incompatible. With cellulose-based polyelectrolytes I liked the syrupy-esque consistency they gave me. I recently started trying out hydroxyethylcellulose again, and that seems to be a pretty good fit “so far”. Though it too might have problems down the line.
It’s true that the premise of my post was to up-front reject certain forms of advice, due to the narrow and specific goal I am after. It’s disappointing that this is still the advice I received, however I will continue to research on my own time and check up on this post to see if anything else surfaces that could help my interests.
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I think it’s difficult to even get a pure “Lauric acid”. Certainly when you get lauric acid in the cosmetic industry it is still a blend of C12, C14, C10 and residual others. It’s just that it has a higher level of C12 than something like lauryl glucoside. There just isn’t any great benefit to getting 100% pure Lauric acid in our industry.
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I’m not in China seeing how the Lauric Acid is produced, I’m just instructing the highest purity chemicals on the market to be delivered to me, and then third party testing it to confirm. I was quoted 90% purity on SLSa, from my long time suppliers. I will see for myself. Lauryl Glucoside was so impure, both when ordered abroad and domestically, that I removed it from my formula. It was easily below 50% purity. Both Lauryl Glucoside, and Coco Glucoside were ‘practical’. I am not after practical, I’m after perfect and isolated.
I understand that it’s not standard practice to strictly regulate the purity on ingredients. However, it is the approach I think is best. Not only does it help with narrowing down specific enhancements to the quality during formulation, it drastically reduces contamination risk.
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Lauric acid as we use it, is not pure. It’s a fraction that was first hydrolyzed, separated, evaporated/condensed, recrystallized….and still, there might be some by-products. This process is time consuming, expensive and not needed. If you want more purity, then you’ll need to use fully synthetic products that use very specific catalytic methods of synthesis, which is what Pharma mostly does since the highest purity level is required, both for safety and performance.
This is all not necessary for us since cosmetic ingredients are safe (not sure what you mean by “enhanced health benefits” from a cleansing product). The best independent toxicologists perform systematic reviews of evidence (something most of us can’t do without that type of training) to assess ingredient’s safety, which you can access through CIR database and COSING. Also, how did you test purity? only using qNMR? Usually, to cover all possible impurities, you use different techniques (atomic absorbance especially for metals, HPLC/GC with different columns and solvent mixtures, mass spectroscopy with an adequate ionizing source, etc.).
Now, to your tests:
- fatty alcohols for sure won’t help with your viscosity if you didn’t form a lamellar phase first (this requires specific ratios of water, FFAA and surfactant)
- MgCl2 helps transition from one colloidal arrangement to a higher one, but this requires a lot of it (if you’re using pure anionics), or you’ll need to also add an amphoteric surfactant to have a quicker salt response, which I don’t see you did
- Na caseinate won’t help build viscosity as much as other polymers, and might increase contamination risk of your formula
- if you’re not using cationic polymers, you’re missing the main conditioning mechanism available for a shampoo, which is coacervation
- Oleamide DEA has the same issue as Cocamide DEA: presence of free secondary amines that could turn into nitrosamines (now, that’s an impurity I would be more focuesd on)
- you mentioned Lauryl glucoside, and that’s funny since when you compare Lauryl glucoside with Coco glucoside, the first one is more detersive, but the second one builds viscosity better and is more gentle with skin, beause of the diverse fatty content in Coco glucoside, so, you’d actually might use Sodium coco sulfoacetate instead of Sodium lauryl sulfoacetate, both for better viscosity and mildness
The bottomline: diversity is always good, especially in real life 🤓. Good luck!
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Only QNMR? QNMR is pretty great for isolating singular molecules and constructing a purity analysis. Not to mention cost effective. It’s hard to say what Lauryl Glucoside does for either of us, because as far as I’m concerned you cannot buy actual Lauryl Glucoside, just “concoction”. And trust me, I am with you 100% on the impurities working in favor of Coco Glucoside, but here we run into a massive conundrum: what is doing what? How are you able to accurately improve a product when you are working with so many unknown variables? I’m guessing a small minority, if even 1% of cosmetics companies are performing third party analysis on their chemicals. I’ve never seen the data publicized by any company working commercial end.
Lauric acid as you use it is probably impure, that is correct. It’s an unfortunate consequence of the barrier to entry for cosmetics being set at ~70% to be considered “cosmetic grade”. I can get a lot higher, I believe (~90%), with SLSa - if QNMR confirms my imported batch.
Oleamide DEA I decided to abandon shortly after writing this post because my supplier informed me it was only available in liquid form which shouldn’t be the case.
I am aware of Sodium Caseinate straying from my initial premise, and made a point of that in the post. However, if it can form micelles with limited surfactant properties, it might be my ticket for a lower surfactant presence in the formula. And I’m not sure there’s any alternatives.
In regards to using a cationic surfactant with coacervation, I aim not to oversaturate the hair, only to provide a light cleanse (without causing damage) while delivering active ingredients. This is the primary reason I went with a low concentrate anionic surfactant. Though it does seem as though cationic, as you put it, would provide a straightforward solution to dry/ damaged hair phenotypes by allowing oil delivery.
If you’ve attempted this, do you know if a polyelectrolytes work synergistically with surfactants when salt thickening? And how crucial is PH balancing during salt thickening?
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To tackle your main issues:
- If your only anionic is SLSA, then 2-3% is way too little for a shampoo, especially to achieve the consistency you want without any other surfactant
- If not Cocamidopropylbetaine, perhaps you could use an amine oxide (it boosts foam, makes the anionic milder to the skin and aids with the viscosity)
- Another option is to use either PEG-4 rapeseedamide or Crothix Liquid (or similar), which could work also in synergy with the amine oxide
- Acrylates-homo and copolymers are also good choices, but I don’t know what standard you use to choose, considering that the many studies conducted for each ingredient were evaluated by independent panels of toxicologists, who considered them as safe
- Finally, if you use the amine oxide or an amphoteric surfactant (like amphoacetates or amphopropionates), then you could Benefit by the addition o fan inorganic salt
I think my comment about qNMR was missunderstood, since you consider impurity anything that is not the molecule you want, while from a safety point of view (both for the consumer and your product), it’s usually something you don’t want in your products, like free secondary amines, 1,4-dioxane, and heavy metals (for the latter, Atomic Absorption is a more reliable tool). That’s what I meant with not suffiecient, and that’s why analytical labs have different equipments. Also, in qNMR, some bands could overlap due to coupling, and there Mass Spectroscopy is key.
Big guys (like P&G, Unilever, etc.) which again, have the best scientists in the industry, take actually advantage of the “non purity” of ingredients. For instance, Sodium 2-laureth sulfate has a distribution of ethoxylates, which has a media of 2 moles. If you’d have only the 2 mole molecule, you’d miss the extra mildness and viscosity response of having both 3 mole and 1 mole fractions, respectively. I’m attaching a screenshot from the book “Detergency of Specialty Surfactants”, where you can see that lower or higher (tan C12) chain lenght, make the glucoside surfactant milder.
About the comment that Sodium Caseinate can form micelles with limited surfactant properties (I asume you mean the interaction of your surfactant with the caseinate, since the latter doesn’t have surface properties), you need to keep in mind that surfactants form micelles in solution above some concentration (CMC). Mixtures of surfactants (especially antagonistic) can form micelles below this concentration. Mixtures of surfactants with some polymers (especially the ones with opposite charge) can also form micelles below this concentrations. That’s how colloids work. From there, to get a viscous fluid with a syrup like appearance, you’ll need to have a higher concentration so you can get worm-like micelles (preferibly entangled) or even vesicles, but again, you need higher concentration. Rheology modifiers can mimic this effect by restricting movement, but you have little shear value.
Anyway, I really hope you can manage to ge tour formula, and try to check the large amount of papers and scientific books on the matter. And don’t stress out too much about having only pure ingredients, just try to minimize only the impurities that are proved to be risky. Good luck!
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I’ll order a sample of Sodium Lauroamphoacetate to test. At a glance it seems fine, is this what you’d personally recommend, or any caveats here? Before I get to work on it, any idea on how Sodium Lauroamphoacetate and Sodium Lauryl Sulfoacetate would interact besides the details you mentioned? Would Sodium Lauroamphoacetate and SLSa achieve thickness with mgcl2 or do I need to introduce polyelectrolytes like before to act as thickening agents? Any clue as to the ideal percentages?
I’ll be keeping SLSa at <3% still.
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Yes, sodium lauroamphoacetate is fine. The common weight ratio (as active matter) of anionic/amphoteric is around 4:1 to 3:1, but when you have low content of anionic, then you could start with 1:1 that is closer to a gel phase. If it got thick but not enough, then you can start adding little by little the electrolite. A cationic polyelectrolite is ideal for performance (conditioning), but ai’d start adjusting the base.
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Some more questions and a revision of the rest of what you said:
β-Casein creates micelles, and I believe Sodium Caseinate is rumored to, so that is why I have placed order for a sample: https://www.sciencedirect.com/science/article/abs/pii/S0268005X96800105, hence my interest in it. It seems to achieve this would possessing surfactant properties.Now, I see you mentioned cationic polyelectrolytes, and polyampholytes. Do you have any you know of? Hydroxypropyl Methylcellulose, and Hydroxyethyl Cellulose are both non-ionic, whereas Carboxymethylcellulose is anionic. To be frank, I’m not sure of the significance of their charge and if it relates to surfactants in a similar capacity. I’m also not sure why Hydroxypropyl Methylcellulose specifically had such a detrimental effect on foaming.
On the subject of Magnesium Chloride, do you have any experience using it over Sodium Chloride? Is there any reason a divalent salt would be comparatively worse than a monovalent salt typically used for thickening?
For PH balancing, are there any “healthy” alternatives to Citric Acid? And why do some formulas seemingly contradict themselves by using both Citric Acid and Sodium Citrate, is it just incompetence or is it for convenience?
Since Sodium Lauroamphoacetate is zwitterionic, would its cationic properties allow for coacervation, and therefore would it make sense to try to incorporate caprylic acid into this solution, and if so, at what concentration? Perhaps it won’t be necessary with this altered formula, but I am curious nonetheless.
I have constructed a sample with 0.4% Citric Acid, 3% SLSa, 1.5% Sodium Lauroamphoacetate, and [0.5%, 1%, 1.5%] Magnesium Chloride, and I am observing no benefit to viscosity. Additionally, there appears to be separation occurring which I suspect is from Sodium Lauroamphoacetate somehow.
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Oof, yeah. Major separation. I’m guessing this is due to impurities.
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I’ll reply more later, but could you make a sample without Citric acid?
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I just spoke with my suppliers and they informed me that Sodium Lauroamphoacetate is extremely impure <30% and in liquid form, meaning that even if I did make it work, it’s not viable unless I organize a custom synthesis - which I’m absolutely not going to do if I can avoid it. I’ve scheduled to return my purchase of the sample to Amazon. It’s truly a shame that no due diligence is done amongst cosmetic chemists. Actually, it’s annoying. It’s delaying this project. It seems like you’re damned to try and use more sophisticated materials when formulating. Any alternatives? I’m still drawn to some of the ideas you raised. Namely reducing concentration threshold using a zwitterionic surfactant, or cationic and how it may relate to salt thickening.
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