Wednesday, August 26, 2015

Why cold process soap doesn't work as a shampoo (for most people)

I've been getting a lot of questions about this topic lately, so I thought I should highlight it again. Most people cannot use cold process soap as a shampoo. Shampoos are generally at pH 6.0 or lower, whereas soaps are alkaline, over pH 8.0. This means CP soaps are not pH balanced for our hair. After shampooing with products out of the right pH range, the cuticle of our hair doesn't lie down, and this can lead to abrasion between the hairs. This is a serious cause of mechanical hair damage, and once you have damage, it's hard to repair it, even with the most intense conditioners.

As a note, you cannot get a soap to pH 6 because it'll stop being soap!  

CP soaps aren't as soluble in hard water as most surfactants. Soap molecules in hard water are converted by double decomposition to form insoluble non-foaming salts like lime, calcium, or magnesium salts of fatty acids. This isn't a big deal on your skin, but it can lead to build up on your hair, leaving it looking dull and feeling kinda crunchy. They won't foam well if there are metal ions in your water - and most water contains metal ions - and they won't foam well in the presence of sebum. Given these properties, CP soap isn't going to remove all the stuff you've put on your hair and you won't get a feeling of being clean (or, ironically, your hair might feel too squeaky clean, which isn't a good thing).

What I make as a shampoo bar is what is called a syndet or synthetic detergent bar, using surfactants. If you're interested in learning more, click the links! 

There are some people in the world who use soap as shampoo and like it, and to them I say "yay"! But most of us will have results that are less than stellar. If you are one of those people, now you know something!


Li Xua said...

Since solid shampoo works similarly to soap and cleans just as well as soap does (unless I'm misunderstanding), I was wondering - couldn't we replace all soap with solid shampoo? Unlike soap, shampoo is formulated with a skin friendly pH, and you have the opportunity of adding all kinds of actives (such as the hydrolized protein and panthenol you incude in your recipe), which sounds pretty good, so why not use shampoo bars exclusively?

Susan Barclay-Nichols said...

Hi Li! Yes, you could. When I'm at the gym or camping, I use my shampoo bar as a body wash and soap and love it! Dove soap isn't a soap - it's a syndet bar with a pH of 6 or less.

Topcat said...

Hi Susan, I am one of those who like to use my CP soap as a shampoo bar. I have shortish, fine, limp hair so I am guessing that any mechanical damage is trimmed away before it becomes noticeable. I do find my soap to be quite moisturising for my hair while cleansing effectively and am wondering if it is the free percentage of oils in my soap that contributes to this conditioning effect? I generally leave between 5% and 6.5% free oils (superfat) in my soap recipes. My hair doesn't feel rough or tangled after washing so this is what I have been telling myself anyway!

Most store-bought soaps are syndet bars (or at least contain surfactants plus soap) and they all leave my skin dry and itchy. Handmade soap leaves my skin soft, supple and balanced to the point that I rarely need to use body lotion. I think too much can be made of the pH of soap, as it is not a leave-on product.

I have just got back to reading your blog after a hiatus of over a year and am loving it, thank you :)..... Tanya