decyl glucoside is and the pH and thickening problems associated with it last week. Let's take a look at a few questions about this ingredient, then look at how we can substitute it into a recipe.
Why is the pH so high? I'm sorry, but I have no idea why the pH is so high for this ingredient. I have searched to the point of annoyance, and I still couldn't find anything. If anyone knows, please share!
What's the safety assessments for decyl glucoside? It's considered non-irritating at 33% or lower in a rinse off product. The glucosides are not considered dermal irritants or sensitizers (this reference and this reference). Having said this, this doesn't mean that there is no change of contact allergies to decyl glucoside (reference and another reference), no matter how rare they might be, which also shows that "natural" or ECOcert doesn't equal completely allergy free! I'm not worried about it, but some might be. (I found a ton of references, but I didn't want to inundate you with them.)
How can I thicken my products with gums? I can't help you there, sorry. I hate the feeling of gums in my products, so I don't use them often, and it really is something you have to figure out in your workshop. Take a look at the thickening post and see what others suggest. But you will have to do some work on your own to figure it out for your specific recipe.
As I mentioned the other day, the pH of decyl glucoside is quite high, so it's not as simple as substituting it for another surfactant in a product. Let's look at this facial scrub surfactant base as an example...
SURFACTANT BASE FOR OILY SKIN TO WHICH WE'LL ADD PHYSICAL EXFOLIANTS
HEATED WATER PHASE
25% surfactant of choice
15% cocamidopropyl betaine
51.5% distilled water
3% polyquat 7 or other cationic polymer
COOL DOWN PHASE
0.5% liquid Germall Plus (or preservative of choice)
AFTER THE PRODUCT HAS ROOM TEMPERATURE BUT BEFORE YOU ADD YOUR PHYSICAL EXFOLIANTS
up to 2% liquid Crothix
Let's say you wanted to use decyl glucoside as the 25% in this recipe, what problems might you encounter? Three immediately come to mind - pH in the alkaline range, difficulties thickening, and a possibly-not-so-nice skin feel.
The pH is going to be seriously out of whack if you use that much in this product. If you're using decyl glucoside with a pH of 7 to 9, it'll be higher than the 5.5 that I hoped for when I made it. If you're using Plantapon with a pH of 11.5, it'll be really really high! You will need to alter the pH with citric acid or another acidic ingredient. (Multifruit BSC is a great addition to a cleanser as a chemial exfoliant and it will reduce the pH.)
When I've made products with 20% decyl glucoside (pH 7 to 9.5), the pH ended up being around 8.3, so I had to reduce it to 5.5 to 6.0! When I've made products with 10% decyl glucoside, the pH ended up being around 7.6, so I had to reduce it again. With 7.5% decyl glucoside, it was 7.0-ish. With my foaming facial cleanser, I used 5% foaming silk surfactant, 5% decyl glucoside, and 2.5% cocamidopropyl betaine and the pH was 6.0.
In the foaming facial cleanser, the one with the pH of 6.0 used various extracts and hydrosols that have acidic pH levels, like chamomile hydrosol, apple extract, witch hazel, and so on, all of which brought the pH down. The only thing I used that would have increased the pH was the decyl glucoside, which shows that it doesn't take much to increase the pH!
What about pH strips? I don't recommend them. They are highly inaccurate. If you use recipes as they are written on this blog, they are pH balanced and you don't have to worry!
With a facial scrub, you'll be using physical exfoliants and those'll fall to the bottom without decent thickening. To get this clay to suspend, you need some thickening, and the viscosity of this product, even with 2% liquid Crothix, will end up being akin to water! I can't even suggest adding something like aloe vera because decyl glucoside doesn't thicken with salt! Practice with your gums and carbomers and see what works for you! You really want to read the suggestions found in the post on thickening if you plan to use a lot of decyl glucoside.
WS suggests this in this post: I use "MaizeThix" modified cornstarch, 5-6% to thicken a decyl glucoside shampoo and it works splendidly. I add citric acid before adding the surfactant to the gel. The final result is neither clear nor cloudy - more translucent.
MaizeThix is the name given to this ingredient by The Herbarie, INCI modified cornstarch, which doesn't give us much information. I'm afraid I can't find it anywhere else. Suggestions?
Skin feel is a personal thing, and it's up to you to decide if you like what you've made. I don't like this much decyl glucoside in a product as the foam feels thin and dry, two things I don't really like, but you might like it. For my foaming facial cleanser, I wanted something kinda dry feeling, so it worked well, but it would be too much in this facial scrub. If I wanted a more emollient feeling, I could add a water soluble oil or ester to the mix, or try using something like glycol distearate or Crothix to make it feel slightly greasier. If you want more foam or lather, you might consider using a third surfactant that offers those qualities or adding even more decyl glucoside. Again, this is up to you to decide on the resulting skin feel and how you can get there!
Join me tomorrow as we take a look at a few more recipes and how to modify them!