A question that I've been getting more and more frequently over the past few years is, "can I use your soap as shampoo?" I give the most honest answer I can, which is that I know many customers who use my soap as shampoo and it seems to work well for them. I actually feel pretty out of touch with the shampoo bar revolution, mainly due to the fact that, well, I don't use shampoo!
A Personal Hair Washing History
Sometime back in the mid aughts I heard about an intriguing concept called the "no 'poo" method of hair washing. As someone already dedicated to pretty minimalist "no more than once a week" hair washing, this sounded like it would be even easier.
For a few years I happily used vinegar rinses as directed by "no 'poo" acolytes, with only the occasional shampoo on special occasions. (While I tried their baking soda recommendations at the start, it did seem to cause hair dryness and frizz in my case, so definitely use with caution) Then, as I got deeper into the world of outdoor education and week long backpacking trips, even the vinegar rinses got pretty sporadic, until, I just stopped washing my hair. Ever.
Now, I'm sure it helps that the only public appearances I make are places like the farmers market and family get-togethers but given that my friends and family have yet to stage a hair-washing intervention, I think my no-washing-ever method works well enough for me!
What is a Shampoo Bar?
...is it just soap?
The first problem I ran into when investigating shampoo bars was that the definition was....um...slippery? It seems that there are broadly two different answers to this question. The version of a shampoo bar that I see the most DIY recipes for is simply a soap bar, often with a few extra sudsy, moisturizing ingredients thrown in like castor oil or cocoa butter which are supposed to be especially good for hair.
If this is what you're looking for in a shampoo bar and it works for you, then yes, you can absolutely use my soap as a shampoo. Tallow and lard are wonderfully moisturizing for hair as well as skin and the soap is mild enough not to excessively strip oils from your hair.
One problem that some people will run into is that soap can start to leave a residue that builds up in the hair. This is especially true if you have hard water. So if you have the type of water that builds up soap scum in the sink, it's likely it will build up in your hair as well. You can find instructions online for vinegar rinses to help combat this but that isn't the solution for everyone. Differences in water hardness along with differences in hair types, I think are what accounts for much of the wide differences in individual experience with shampoo bars.
Another factor is that hair care buzzword, "pH balanced". If you've never thought much about hair care before (in which case congrats on reading this far!), then you've probably never thought much about the pH of your shampoo. But it turns out that since your scalp is slightly acidic (in the 5-6pH range), the alkalinity of soap (8-9pH) can disrupt that balance and in some cases cause damage and dryness. And there is no way to make soap acidic! Any shampoo bar that claims to be pH balanced is not soap, instead it is that other popular form of cleanser:
If you dig a little deeper into the DIY recipes, you will eventually find recipes for shampoo bars that are based on synthetic surfactants (soap is also a mild surfactant but is considered "natural"). Some common ones are Sodium Coco-Sulfate (SCS), Sodium Cocoyl Isethionate (SCI) and Cocamidopropyl Betaine. They are derived from coconut and can be pH balanced with powdered acids (stearic acid or citric acid, for example) and are considered to be gentle on the hair.
The downsides of surfactant based shampoo bars, depend mostly on where you're standing. Some folks dislike the mostly synthetic ingredients of these bars and find that they wash away and get used up too quickly. These are very easy opinions to have if a soap based shampoo bar or the "no 'poo" method works for you. However, other folks have had bad experiences with soap based shampoo bars, finding that it leaves too much waxy residue overtime or can be drying to their hair. After all, like soap bars, surfactant based bars still have the advantage of being much more eco-friendly than liquid shampoo. They are much lighter to ship than liquid shampoo and require little to no packaging.
Eco-friendly Hair Washing
So if your main goal is to make your hair-washing routine greener, than ANY shampoo bar is better than that bulky bottle of liquid shampoo that is so ubiquitous. If soap works for your water and hair type then keep at it! If it doesn't, well, shunning the ingredients of surfactant based shampoo bars because they are synthetic seems like letting good be the enemy of perfect. If you want to know more about hair chemistry and shampoo ingredients, here is an excellent short podcast episode from the BBC that addresses cheap vs. expensive shampoos, as well as liquid vs. solid.