[RobertG]

Are you able to coat both sides of a flat metal surface with your coating?  If so, you could rig a relative (suitable for comparisons) static friction measuring device with a C clamp, 2 durable pads, a spring gauge or a pan + weights, and string.

[RobertG]

Part of the problem is the perception on the part of the user vs. the perception of people around the user.  Your sense of the smell of any particular thing fatigues rapidly, so what you barely notice once you leave the bathroom can still be very noticeable to other people who get close to you.

[RobertG]

Are sulfonates & sulfosuccinates as bad for the environment as sulfates?  Yes, to the extent they’re bad, which is practically not at all.  With normal sewage treatment, their breakdown products are all equally harmless.

There has been reported under some conditions persistence in the environment of surfactant moieties of the alkylphenol type, which may have adverse effects.  However, that has nothing to do with whether that moiety is capped by a sulfonate, sulfate, or sulfosuccinate group.  (Practically speaking, nobody makes alkylphenol sulfosuccinates, and alkylphenolsulfonates are actually mixtures of sulfonates & sulfates.)

[RobertG]

Poly(ethylene glycol) is made from ethylene oxide, in the process of which some 1,4-dioxane is produced as byproduct, some of which, more or less, must find its way into the product as a contaminant.  1,4-dioxane has recently been determined by the Int’l Ass’n for Research on Cancer to be a possible human carcinogen based on animal experiments.  (As time goes on, we’re finding weaker & weaker carcinogens, because the stronger, more definite ones were evident first.)  If it does have an effect in humans, it would probably be by inhalation.

Phenoxyethanol gives some people a rash, “burn”, or tingle at concentrations which don’t bother most people, and which are used for effective antimicrobial preserv’n.

[RobertG]

If Stepan has the NaOH listed as “neutralizer”, then I’m guessing it was either their mistake or they had something in there that needed neutralizing that when you modified the formula you left out.  Amine oxide surfactants because they’re made under alkaline conditions tend to come in slightly alkaline IME.  I agree with the others that you don’t have enough NaOH to work as a caustic cleaner, but “too much” for anything else I can see.  Also that if this is for direct application as on a mop or from a spray bottle, to then be wiped off without rinsing, it has too much surfactant.  The limonene looks like too little to be a solvent, too much to be a preservative or perfume, although if it’s the only preservative it may not be enough!

[RobertG]

Elainec, you need to step back & explain what your object is.  What properties do you want your product to have in particular, especially those that would make it different from what most people would have on the shelf?  I gather you want to make something primarily for cleaning hard surfaces by hand.  Is that right?

“Cocamidopropyl…” what?  Betaine?  Amine oxide?

Why do you want washing soda in there?  Your thrust seems to be primarily toward making the product skin-friendly, but making it alkaline isn’t going to help.  Washing soda’s more like a thing someone would want in a dishwashing machine than in hand washing.  It might help a little in mopping the floor, but you’re not likely to make a single formula that’d be anywhere near optimal for both those purposes.

[RobertG]

I don’t understand what you mean by “the viscosity of the final product” when you write that it’s a “soap bar”.  Ordinarily one doesn’t refer to viscosity of solids.

It is indeed a strange looking ingredient list for a cake of soap.  It looks like the ingredients list for a lipstick or deodorant stick.  The only soap that’s already in there is sodium stearate, which itself produces very little foam.  If the “phosphate salt” were trisodium phosphate, it might be alkaline enough to turn the stearic acid into sodium stearate, and if any is left over, to saponify the olive oil or the beeswax, but I have a feeling that’s not what’s involved here.

Are you maybe trying to make cold cream to pack into jars?

[RobertG]

The tools you’d need to do your own microbiology?

autoclave (pressure cooker will do)

incubator

supply of culture plates/dishes

inoculation loop or supply of disposable sticks

pipets (You can buy presterilized disposable.)

burner (gas stove is OK)

supply of culture medium nutrients & agar for jelling (You can buy pre-poured & pre-sterilized.)

starter cultures (available from ATCC)

refrigerator

tubes for slants or stabs

None of these is very expensive (assuming you already have a gas stove & refrigerator), and only the incubator is what you might consider a precision device.  However, unless you really want to get into this sort of thing & do it a lot, paying others to use their skill & equipment is going to be more cost-effective, and not require you to practice to get good at it.

[RobertG]

I think the concentration of sodium laureth sulfate may be even lower than stated, because where do you get it as a dry material?  It’s probably a solution which may be 30%-70% actives.

[RobertG]

The aforementioned statement about “cosmeceuticals” changes nothing and IMO isn’t even a clarification.  It doesn’t make anybody’s job easier or harder.  It’s still the case that some products are both cosmetics & drugs under state & federal law, & so subject to the laws regarding each.

There are some categories of definitions in food & drug law such that a product’s satisfying the definition of one thereby is exempted from consider’n as the other.  For instance, FDA has the statutory authority to treat a product as either a drug or a medical device, but not both, if it has some properties of each, based on which it acts as primarily.  That’s not the case between drugs & cosmetics, however.

[RobertG]

I’d use different words for some of them.  “Detergent” means “cleanser” or “cleaner”, so I wouldn’t have it as a component of itself.  Maybe you meant “surfactant”.  “Exfoliant” could be broken down into “abrasive” & possibly other categories that encourage desquamation, but “abrasive” is a type of detergent too, and it’s not clear that exfoliation should be considered only a category of cleaning, unless what you mean by “cleanser” is anything that aids in the removal of anything, which is reasonable.

“Film-forming” is a term also used in patent descriptions & elsewhere to include the formation of transient aqueous films such as soap bubbles, so maybe you want to specify “film formers” further.

Also, some of your categoriz’n doesn’t really work taxonomically (hierarchically).  Under “conditioners” you have some functional & some compositional ways of categorizing, so your categories aren’t all parallel.

I have about the same criticism of “functional” vs. “aesthetic modifiers” as the others.  What I think you were driving at is a distinction between those whose function is direct in use and those whose function is to deliver those other functional ingredients.

[RobertG]

I don’t have direct access to the full paper, but I can tell you that something like this was suspected 20 yrs. ago when I was a researcher in the field.  That is, melanin was suspected simultaneously of being UV-protective & UV damage-mediating.  Every molecular species that can hold such an excited state is a candidate both to quench and to propagate damage from free radicals.

[RobertG]

Why is urogenital irritation by surfactants specific to a region of the body rather than to a tissue type?  Howard Maibach was as puzzled by this as I am.

[RobertG]

Whew, I ran up against the character limit & I was only a little ways into gushing about my experience.  Anyway, David, you’re partly on the right track but there are still some gotchas.

First, decide, what properties you want to optimize.  You’ve already done that.  Also, you’ve listed what you consider to be the candidate ingredients for doing so, based on general principles.  That’s good, but that will give answers that are partly right, partly wrong, when it comes to mixtures.  For instance, my experience seemed in line with the previously published data that say alkamidopropyl betaines & at least certain anionic surfactants reduce each other’s irritancy, and showed it was probably true of more anionics than had been known about.  OTOH, lauryl sarcosinate had exactly the opposite foam characteristic in my mixtures than when studied alone or in some other mixtures.

Also, consider the possibility that reviews rating the overall performance of certain ingredients may be based in part on criteria different from what you’re interested in.  You wrote, “Disodium Laureth Sulfosuccinate – did not get a good review here”.  I haven’t seen that review, but I’ll point out that the industry doesn’t use sulfosuccinate esters as much as it might, because of the instability of that ester linkage.  Carboxylate esters are labile, which fact is both the boon & the bane of soapmaking.  Were they not, we may not have discovered soap as early was we did.  However, many kettle process soapmakers have had the experience of saponification happening too fast.  Well, it’s true of sulfosuccinate esters too — not as much when there are linking groups introduced as via ethoxylation as in the direct alkyl esters — but still enough that mfrs. aren’t so happy making them, and don’t keep them for long, and formulators may be somewhat reticent to use them.  I’ve had my mixture react quickly & unpleasantly with a lemon verbena fragrance oil one formulator tried, for instance.  But once you eliminate such possibilities, it turns out that the sulfosuccinates in my mixture are reasonably stable; the batch I had made by FMI has rather clotted & tends to separate, but it’s over a decade old now, which would be asking a lot for most liquid products.

(Acyl isethionates are carboxylate esters too.  If you’re very partial to using certain fragrance or essential oils, and you want to incorporate a carboxylate ester such as an isethionate, sulfosuccinate, sulfoacetate, lactylate, or glutamate, better check it out at the pH & temperature you expect to process at, to make sure that FO or EO doesn’t break it down.)

Or it may be that people are just generally down on ethoxylation products now, concerned with 1,4-dioxane contamination.  That may or may not be your or your customers’ concern, however.  And even if it is their concern, that may not be as great a concern once your products hit the market.

Also, sodium isethionate can be used for thickening, but is it any better viscosity builder than simpler salts in shower gels that don’t incorporate acyl isethionates?  It’s going to be more effective in some mixtures than in others for the cost.  Similarly, cocamidopropyl betaine will extremely thicken some mixtures and hardly affect others.

[RobertG]

I can lay out my experience, the product of which is explained at http://users.bestweb.net/~robgood/lather.html

When I became aware that someone I knew had 3 children who liked playing in thick foam in the bathtub, such as bubble bath or shaving cream, but that the oldest of them would suffer an irritant vulvitis or vulvovaginitis if too much bubble bath was used or if she sat in shaving cream, I took that as a challenge.  I’d dabbled in foaming surfactants before, and was familiar with literature on them as concerned general mildness — in particular the property of mixtures of certain betaine & anionic surfactants to reduce each other’s skin & eye irritancy, and also of sulfosuccinate surfactants to stretch the foaminess of more irritating anionics without adding to their irritancy.  I wasn’t sure this would work in the particular case of urogenital irritation, which involves both skin & mucous membranes and affects a region rather than a tissue type, but I figured it was worth a shot.

I started with a 3-component mixture of sodium lauryl ether-3 sulfate, lauramidopropyl dimethyl glycine betaine, and diammonium lauryl sulfosuccinate monoester, using the last component as the chief surfactant, the betaine as both adding to & stabilizing the foam, and the ether sulfate as the most variable component, down to 0 or up to approximately equal to the sulfosuccinate.  I quickly settled on what I considered to be an optimal ratio of sulfosuccinate to betaine, and found the foaming qualities of the mixture to be most responsive to changes in the ether sulfate, from most lathery but least voluminous & stable at 0 of that component to fluffier & more stable (when left undisturbed, but becoming more fragile if played with) as that component was increased.  The same could be achieved by increasing the ratio of betaine to sulfosuccinate, but only by larger degrees, i.e. less responsively.

This was a time when makers of such surfactants were much more generous about sending out free samples, so I had enough to play with in small amounts, and could use volumetrics such as pipets for small experiments because the components were supplied as solutions.  The solutions came with their own preservative, which was nice because the final product could be formulated without additional preservative as long as the total was undiluted; I had no intention of watering the mixture if I could help it, since it would not be more convenient for users to pour out larger volumes.

I also experimented with powdered ingredients to make a tablet product.  Disodium lauryl sulfosuccinate was conveniently supplied as a powder.  Of alkamidopropyl betaines, however, all I could get was an experimental spray-dried cocamidopropyl betaine from Henkel, which was hygroscopic & gummy but still served.  Such a mixture worked, but since I wanted to optimize components of which many were supplied only in solution, and I didn’t want to complicate life by using adsorbents or using drying technology, I did most of my experiments in solution.

I went beyond the initial test subjects (the family I made the stuff for), but it was hard to find good, reproducible cases of people sensitive to vulvitis, vaginitis, or (male or female) urethritis from soaps & other surfactant products likely to contact their genitals.  Far more people suspect they or their child have such a problem than can prove they have it.  Anyway, I found with a wider subject base that sodium lauryl ether-3 (or 2.5 mole EO or whatever undisclosed ethoxylation is actually used) sulfosuccinate, which I’d previously determined acted like a mixture of ether sulfate & alkyl sulfosuccinate in the 3-component system in terms of foaming, was even less prone to cause vulvitis in a very stringent test on someone who usually suffered such a condition if they let soap contact their groin in the shower, and who was pregnant at the time of the test, which generally increases such sensitivity, and who used my mixtures both as bubble bath & directly as peri-vaginal wash.  So I dropped the ether sulfate entirely in favor of replacing some of the lauryl sulfosuccinate with laureth sulfosuccinate.

I tried various other anionics here & there, discovering for instance that sodium lauryl sarcosinate, which is ordinarily viewed as a more lathery, less fluffy foamer, acted similarly to the ether sulfate in making the 3-component mixture produce a fluffier, drier, more polyhedral foam.  I also tried out components supplied with longer alkyl moieties such as myristyl sulfosuccinate (experimentally produced by McIntyre) and a great many betaine varieties.  I found that a mixture of lauramidopropyl and palmitamidopropyl/cetamidopropyl betaine made foam that was better in all respects than the more commonly used cocamidopropyl betaine.  Fortunately lauramidopropyl betaine is widely available; unfortunately palmitamidopropyl betaine is not, unless you want to make a large order.  Perhaps if the Bissett-Mao formula of Ivory Dishwashing Liquid had stayed on the market (I eventually met Don Bissett at a photobiology conference, where his interest was in sunscreens and mine was in melanin as UV-protective), palmitopropyl betaine would be a commoner article of commerce.  I still think there’s a lot of potential for makers of toiletry surfactants to vary average chain length of the alkyl groups, the way soapmakers do by varying the proportions of fats they use.

For my patent I had to devise a way to measure density of foams.  I’m indebted to a tech at the lab I employed who figured out drilling holes in sample vials would allow them to be packed with foam for weighing without air pockets in the bottom.

I did a lot of esthetic testing, mostly with children, to verify that children mostly did prefer to sacrifice foam volume to density, and that many adults liked it that way too.  So I tended to refer to the mixture as “lather bath” rather than “bubble bath”.  A few children, though, didn’t like the way dense foam blocked their view of bathtub toys.

I eventually did find a test subject who, if he took a bath with my mixture 3 days in a row, did experience some urethritis.  Surprisingly, it was a male subject, one of the few grown men I got to try the stuff.  It still allowed him to use it much more often than he could use common bubble baths w/o pain, but it said the mixture’s irritancy was not 0, just far lower than that of anything else I could find that was this foamy, and low enough to make a difference to sensitive users who wanted to bubble-bathe, especially frequently or for long soaks or with lots of foam, or to wash their groin with something stronger than plain water — or to masturbate with!  I wouldn’t recommend it as genital lube under ordinary circumstances, but only if you’re going to be in a bath anyway.  I did not try testing its efficacy as spermicidal foam, and suspect it would not be anywhere near as effective as nonoxynol-9, given the ability of nonionic surfactants of that class to depolarize cellular membranes.  (There’s a pretty simple test for that potential, though: apply a solution to your lips & wait to see if paresthesias or numbness develop.)

I also tested it for foam dancing.  It worked spectacularly well as concentrate in the machine of one Miami entrepreneur, who tested such machines in his shop driveway & invited neighborhood kids for a foam party.  It rained when he tried mine, and was surprised at how long the foam held up rather than being quickly knocked down by rain as the solution the usually used was.  But his was cheaper, from a large production stream for baby shampoo.