Wednesday, April 21, 2010

Surfactants: Incorporating mildness into your creations - overview

Surfactants, by their very nature, are irritating to our skin. The goal when creating surfactant based products is to reduce the irritation to our skin by using milder cleansers, creating blends that enhance mildness, and adding ingredients like cationic polymers, proteins, or emollients.

When a surfactant comes into contact with our skin, it can bind to the surface and denature our skin's proteins. It can interact with the lipids on our skin and disrupt the organization of the stratum corneum lipids, which can lead to increased dryness and increased trans-epidermal water loss. Surfactants can remove the natural moisturizing factor in our skin, leading to a reduction in the ability of our skin to attract moisture from our environment. If they annoy our skin enough, the anti-inflammatory response can kick in leading to itching, drying, and redness. (This is one of the reasons you don't want to leave an anionic surfactant on your skin as a leave-on type of product!)

Okay, now that I've scared you into never wanting to use surfactants ever again, let's take a look at how easy it is to increase the mildness of our surfactant mixes so we won't have these horrible side effects for simply washing our faces!

We can increase mildness by...
  • using only very mild surfactants;
  • reducing the concentration of surfactants in our creations;
  • modify the behaviour of the surfactants; and
  • protect the skin's surface by including various ingredients.
Using only mild surfactants will create a mild creation. You can create some very mild cleansing products using decyl glucoside (non-ionic) with cocamidopropyl betaine (amphoteric), which we see in baby products. We can create very mild blends with anionic surfactants (see below), then combine them with the non-ionics and amphoterics to creating something even milder!

If you want to try making something without anionic surfactants, you could make a really mild blend using decyl glucoside, cocamidopropyl betaine, and PEG-7 cocoate that will re-fatten the skin, thicken quite well, and offer mild cleansing with not-so-great foam. This would work well as a very mild facial cleanser or make-up remover, but for something like a body wash, we really do need our lovely anionics.

I like using a combination of SCI, cocamidopropyl betaine, and DLS mild for very mild cleansing. Combine this with some of the ingredients I'll mention in the next sections, and you have yourself a very mild cleanser with great foam and fantastic skin feel.

Reducing the concentration of the surfactants in our creations is really simple. Just use less. I know, this sounds really glib, but it's true. If you are making a facial cleanser, but find that it's a little too much for you, you can take that mixture, add about 33% more water and turn it into a foaming cleanser - if you don't want to thicken it - or add some more Crothix or salt and thicken it up!

Combining surfactants is a great way to modify the behaviour of the surfactants in our products and it's a really simple way to increase mildness. Adding cocamidopropyl betaine (amphoteric) or non-ionic surfactants like decyl glucoside or even polysorbate 20 will reduce the potential irritancy of an anionic surfactant dramatically, and you can combine surfactants to increase mildness. There are two theories about why this works.

Theory one: Surfactants tend to form micelles when they are added in proper concentration. Some surfactants aren't that keen on joining the group and they float around in the water as monomers (polymer means many, monomer means one - they're loners). These monomers are what bother your skin and cause irritation as they interact directly with your skin's proteins. When we add a few surfactants together, they form larger and more stable micelles, which reduces the number of monomers, which reduces the irritation.

Theory two: Surfactants compete for binding sites on your skin. When you add a milder, secondary surfactant it occupies the spot to which the first, less mild surfactant could have bound. So the less mild surfactant has no where to attach to your skin and is washed away.

A little more chemistry...when the polymers interact with the micelles, the micelles become more hydrophobic. Increased hydrophobicity means less adherence of the surfactants to your skin. We know that adherence of surfactants to your skin is a key element in that feeling of tightness after washing, so less adherence equals less irritation.

We can add polymers, proteins, and emollients like dimethicone to our products to increase the mildness and help protect our skin. When we add a polymer - like polyquat 7, honeyquat, or dimethicone - they incorporate into the micelles and reduce the relative amount of monomers in the solution. As the monomers are the culprits in causing irritation, this will reduce irritation. As well, they compete for those binding sites so the less mild components of our cleanser will wash away.

When we add proteins, we want to add the higher molecular weight proteins like oat or wheat to form a film on our skin. Silk is lovely for dry skin types, but if it penetrates your skin, it kinda defeats the purpose of forming the film. Proteins are great additions to surfactants mixes - they increase foam stability and density and increase the feeling of creaminess and slipperiness.

Note: If you can't get proteins, then cocamidopropyl betaine is a great alternative!

Emollient ingredients - Crothix, glycol distearate, water soluble oils, fatty alcohols (like cetyl alcohol), and silicones - will help reduce the disruption of the stratum corneum lipids, which can lead to an impaired barrier function. You can use a lotion after bathing, or you can incorporate some of these ingredients into your surfactant mixes. (I'll be going over the specifics of Crothix and glycol distearate in the upcoming posts on increasing viscosity in our products. For now, click on the links for more information).

This is what we're seeing a lot of in the moisturizing body washes. Generally they'll use mineral oil with an emulsifier as the emollient, but you can use a variety of different ingredients to get that same effect. I like using water soluble oils - I have sunflower, jojoba, and olive oil - at about 4% for adding moisturizing.

And don't forget your humectants! One of the big problems with incorporating humectants into your surfactant creation is this - they wash off. Sodium lactate is pointless in a surfactant mixture because it'll wash off and fail to offer any form of humectancy! Glycerin and urea (in urea form or Hydrovance) are your best choices for humectants, as well as one of the glycols like propylene or butylene glycol. Glycerin not only increases your bubbles and lather - bonus! - but can help with barrier repair, improved stratum corneum hydration, and reduces trans-epidermal water loss. I add it at 3%, but you can go even higher to 5% - 8% in a body wash if you have really dry skin. Most of this will wash off, but if you get even 1% to stay on, that's a good thing!

Finally, we can include some anti-inflammatory ingredients - like aloe vera, witch hazel, white willow bark, or salicylic acid - but it's better to reduce irritation than to treat it after the fact!

If you take a look at my basic body wash recipe (which we'll be modifying like silly over the next week or so), you'll see I have tried to include every single feature listed here.

37.5% water
15% cocamidopropyl betaine
15% Amphosol AS-90 or SLeS - mild anionic surfactants
15% BSB or LSB - gentle anionic surfactants
5% aloe vera - film former
3% glycerin - humectant
3% Condition-eze 7 - cationic polymer
2% cromoist or other hydrolyzed protein
2% panthenol - great humectant, skin barrier repair
1% fragrance or essential oil
1% liquid Crothix - re-fattening our skin
0.5% preservative
Colouring, if wanted

Join me tomorrow for more fun with surfactants! 


pish said...

W-O-W I gotta tell you how totally blown away I am by all the info you've got here. I feel like I'm taking an insanely interesting chemistry course! THANK YOU so much for sharing!

Since Condition-eze doesn't seem to be findable in Canada, would you recommend replacing it in this recipe with dimethicone? Or just leaving it out?

Oh and THANK YOU some more for introducing me to Voyageur!! Awesome.

Susan Barclay-Nichols said...

Hi pish! Thanks for your kind words. I love sharing what I've learned, and I'm always happy if other people find it useful.

You can use honeyquat - found at Creations from Eden in Edmonton - or dimethicone. I love honeyquat - it's a humectant as well as a cationic polymer, so it does double duty - and I love dimethicone as well.

You can put these things in or leave them out - it's up to you! Personally, I consider the cationic polymers so useful - I use them in toners, facial washes, body washes, hair care products - I would encourage you to get some if you can!

I love Voyageur! They are awesome. Their customer service is amazing, and they support my youth craft groups by donating so much stuff so we can things like bubble baths, body washes, and hair care products!

pish said...

Sweet - another Canadian supplier! Hahaha, you are such an (awesome) enabler!! Thanks again.

M said...

HI: I absolutely LOVE your blog, I learn so much from it. I make creams/lotions and would like to start with body washes. Please recommend suppliers in the Toronto area for sufuactants, I usually buy other items from NDA(shipping from Voyageur can be pricey at times). Thanks so much! MK

Susan Barclay-Nichols said...

Hi M! I'm afraid I don't know suppliers in the Toronto area, other than NDA. Surfactants can be hard to come by in Canada. Here are two other supplies - I've never used them, so I can't guarantee anything.

Aquatech (Toronto)
Saffire Blue (they have SLSa and cocamide DEA)

You can try the suppliers I have on my local list on the right hand column of this blog, but they are local to B.C. and I don't know about shipping costs. Sorry I couldn't be more helpful. If anyone else has suggestions, please post them!

kontakt said...

I have to agree, your blog is SO useful. Thanks a lot for writing it!

This I wonder, though. Water-soluble oils? Those you mentioned aren't really water soluble, are they?

I've been wondering about vegetable oils in cleansing products (body wash, shampoo) for some time. Won't the surfactants - the detergents - just dissolve them and "occupy" the surfactant so there is less detergent to clean your body, i.e. you could get the same result by simply using less surfactant in the first place and skip the oil?

Bob Goodman said...

Well, Kontact, I've often thought the same thing, but...have you ever washed dishes and wound up with greasy hands? You got the dishes cleaner than when they started, and your hands wound up greasier than when they started. The only way that could be is if an equilibrium is reached between oil being picked up by detergent and oil being deposited by it. The oil on your hand is mostly not the same of whatever oil your hands started with, so it stands to reason that if you wash with a product like Dove, and use enough of it at one time that the amount of stearic acid used is much greater than the amount of skin oil you started with, that much more of the deposited fatty material will be fresh, clean grease from the cake of Dove, than the dirty grease your skin started with, because it would all equilibrate (if you got to equilibrium conditions, which probably doesn't happen but might be approximated).

You would get the same effect of an "oil change" by using the ancient technique of rubbing oil on your skin and then strigiling it off, or by bathing with bath oil and a washcloth.

However, since I brought up Dove, Bob McDaniel once mentioned (might've been on Compuserve's soap & candle making forum, or might've been Melody's e-mail list) that in blind tests, users couldn't tell the difference in effect between superfatted and non-superfatted soap, or between Dove/Caress and the same composition without the "one quarter cleansing/moisturizing cream/bath oil", i.e. the stearic acid.

Susan Barclay-Nichols said...

Hi kontakt! Wow, great question!

Actually, the oils I mention do come in a water soluble form - I have some samples from a company in Ontario that are PEG-something or other macadamia nut, sunflower, jojoba, and olive oil.

You can increase mildness by reducing the surfactants, but then you have to increase the thickeners. By adding some emollient ingredients, you can increase the mildness and keep your surfactant levels the same.

There is some displacement of the surfactants as they are emulsifiers by nature, and some of the good oils will come off when you are rinsing off the oils you don't want on your skin or hair, but Bob's right - you will feel the oils on your skin after using a body wash (for instance) with extra emollients.

kontakt said...

Cleaning = oil change, for those of us who just can't remove oils without adding new ones or we get eczemas. Interesting thought, Bob. No, I haven't ever got my hands greasy after dishwashing. I add more detergent/dish washing soap before I am anywhere near that situation, but I understand what you mean. Still... your dishes might be CLEANER, but I would hesitate to call them clean. Now, the question is how clean we should wash our skin. In a way, not too clean.

PEG-modified oils, I get the picture. I have some PEG-olive-esters, or similar. What is the difference in the end result, I wonder, from adding this and adding regular oil. Intuitively it seems more right though to add fatty surfactants - in the chemical aspect of the word, not the "bubbling cleaning" type - than regular vegetable oils.

I'm one of those irritating people who like to know how and why, not only if...

Susan Barclay-Nichols said...

Hi kontakt! I'm a who, what, where, when, why, how, and how come some more kinda girl, so I understand the need to know!

The difference I find between water soluble oils and regular oils in surfactant mixtures is the solubility and clarity.

If I use a regular oil, it will float to the top of the mixture, so I need to use an emulsifier. Most emulsifiers will reduce the foam in the mixture and might make it cloudy (depending upon the oil, the emulsifier, and the fragrance oil I use).

If I use a water soluble oil, I can avoid using an emulsifier, so it's less likely to be cloudy. It's also less likely to come out of the mixture and float on top, which you'll find if you don't use enough emulsifier.

I also find I have a lot of uses for water soluble oils - I like to use them in sprays, make-up removers, and light moisturizers - so it's worth it for me to have them around. If you don't want to order any, you can do a mixture of polysorbate 80 and the oil - usually 1:1, but it can be more or less, which you'll find out through experimentation - and add it to the surfactant mixture.

kontakt said...

I've noticed some oil floating on top, yeah! So probably I should try my olive oil-PEG-esters instead.

BTW, I'm "moz" on the Dish.

Nyx said...

I left a comment earlier, but somehow it ended up not logging me in to my google account, so it ended up being anonymous. Sorry about that.

I recently made a facial cleanser and used a mix of water and 30% Decyl Polyglucoside. It is very thin (because it is mostly water) and the surfactant sometimes floats to the bottom so I have to stir it to disperse it. I have some Polysorbate 80 and Peg-7 Olivate. Could those be used to help the surfactant stay dispersed?

I was wondering what I should use to thicken it? I don't really want to add another surfactant like Coco Betaine beacuse I have really dry skin. I have some xanathan gum, but I am not sure if that would cause problems with the way the surfactant worked. I just need a super gentle and moisturizing cleanser.

iliana said...

hi, i love your blog, have you ever emulsified a shampoo? i mean using oils in the formula

Susan Barclay-Nichols said...

HI Iliana. Check out the hair care section of the blog for recipes for shampoo.

Christopher said...

Susan, will modifying a surfactant OR binding the skin sites actually reduce the cleaning power of a surfactant? If yes, how much reduction of cleaning power?

I read we can do this by adding nonionic surfactant, amphoteric surfactant, stearic acid, palmitic acid, HMP (hydrophobically modified polymer) and polyquaternium-7. Glycerin is not mentioned because it is not effectively delivered into the skin for protection. My question is still the same, by adding one or a few of these to the surfactant system will the primary surfactant's cleaning power be reduced.

I seriously need good cleaning power at the same time does not take away my lipids and proteins. I am going for 15% sodium alpha-olefin (c14-16) sulfonate as I understood this has half of the destructive power of sodium lauryl sulfate. However, I do not know which additional ingredient to make this surfactant while not reducing the cleaning power of sodium alpha-olefin (c14-16).

It makes no sense if additional ingredient reduces the cleaning power because it would be equivalent to using less surfactant. Less surfactant means I must use a lot of the product in order to thoroughly clean myself.