As you can see from the listing text of all of our shampoo products, solid and liquid alike, we recommend following up each wash with a vinegar (or lemon juice, etc.) rinse. What we don’t tell you in those listings is why we recommend using a vinegar rinse on your hair after washing with our shampoos, so I thought I’d take a bit of time and explain the reasoning behind the recommendation.
There are three main reasons for using a rinse of this kind with natural shampoos. First, unlike most commercial shampoos, they do not contain SLS or other high-test detergent/surfectants, and indeed the only surfectant they contain is, well, soap. Specifically, potassium-based soaps, which are much more soluble in water than sodium-based soaps, but are still less soluble than the detergents in other shampoos, which means that especially in hard water they can, over time, lead to a buildup in the hair. Rinsing after every wash with a quart or so of water containing a tablespoon or two of vinegar or lemon juice prevents this from happening. It also helps remove buildup from styling products or mineral scale from said hard water, at the same time.
Second, there is a pH balance issue to resolve. Human skin has a pH in the 5.4 range, but the natural shampoos tend to have a pH in the neighborhood of 9. The skin of your scalp will re-balance its pH to its desired level in time anyway, but it is best for the health of your hair and scalp to give it a bit of help in doing so, which the weak acid of the recommended rinse will do. This can also help to prevent itchy or flaky scalp, as having the pH out of whack is one thing which can trigger that effect. This and the above effect are among the reasons shampoos in other formulations became popular in the first place, but as natural shampoos are far more gentle on your hair and scalp than the SLS-containing kind, the extra few moments it takes to add the rinse to my regimen is a tradeoff worth making, in my opinion.
Third, a vinegar rinse will help close the cuticle of the hair shaft, making hair less frizzy, shinier, and stronger. This is one area in which anyone can benefit from using this technique, not just those who use natural shampoos. Anyone who struggles with frizzy hair, or gets split ends quickly, or whose hair is dull or breaks easily, is a good candidate for seeing improvement in the hair within a few weeks of starting to use a rinse of this kind.
So, what sort of vinegar to use? I usually use apple cider vinegar, personally, though I have used regular white vinegar and lemon juice as well. I have had good results from using herb-infused vinegars designed to benefit hair in various ways, and indeed am intending to offer some of these for sale at some future point. But a bottle of vinegar straight from the supermarket shelf will do just fine.
A few caveats, in closing:
1. I have no personal experience in the effect of a vinegar rinse on color-treated hair, and my research into the matter has produced contradictory answers. My suspicion is that temporary/”wash out” hair dyes are washed away much more quickly if using vinegar rinses, but I don’t quite know how it would have any effect on the more permanent coloring methods. Still, I don’t know for certain that it doesn’t, so use this technique at your own risk if your hair is colored.
2. Dilute, dilute, dilute. Never, EVER use more than 50% vinegar in your rinse water, and more like 5% is probably better. I make a two-quart pitcher of rinse every time I wash my hair, because I have thick, hip-length hair to rinse, and I still use less than three tablespoons of vinegar in that much water. If you use too much vinegar in the water, any benefits you might have seen will be overridden by damage you are doing to your hair from that much vinegar.
3. To re-rinse, or not to re-rinse? Opinions are divided as to whether you should rinse your hair with plain water again after using the vinegar rinse. Personally, using such a dilute rinse as I do, I usually don’t bother, and I still don’t end up smelling of vinegar even as long as it takes my hair to dry. I’m pretty sure this one is a matter of personal taste, however.
And that’s what I have to say on the topic of vinegar rinses! I hope it’s answered your questions, but if not, ask away, and I’ll do my best to fill in whatever I left out.