in this post: I was wondering if there might be any science to back up using a vinegar rinse? I agree that using baking soda to wash hair is a terrible idea, but I have found a vinegar rinse (after shampooing, before conditioning) invaluable. My hair is much smoother and more manageable. I have heard the acidity closes the cuticle, but am yet to see the scientific backup to this. One odd thing I found - I once accidentally did the vinegar rinse between the 1st and 2nd shampooing, and it made the 2nd shampooing impossible. I can't remember exactly how, just that the shampoo wouldn't 'go' through my hair somehow, and I wondered if the shampoo couldn't open up the cuticle after the rinse. My question is, is this, or some other reason, at least theoretically possible? I use cheap white vinegar because I think using apple cider vinegar would be a waste of money, about 1 part vinegar to 10 parts water. I have also used very dilute citric acid and found the same positive effects.
Click here for more information on the cuticle! And look at the picture above.) We want our cuticle scales to lie as flat as they can so they won't be torn off or won't allow stuff to pass into our hair shaft. We do that by using things like conditioner that are positively charged and will adsorb to the hair strand to create lubricity and reduce friction. (Click here for information on what damage means to our hair and how it happens.)
As an aside, cationic polymers like polyquat 7, polyquat 44, or honeyquat - amongst others - improve the adhesion of our cuticles to the hair shaft, which makes them harder to remove when we damage them through friction, like when we comb our hair or get it caught in the door of a car! Cetrimonium bromide is also awesome for this! (Reference: Handbook of Cosmetic Science & Technology, 3rd edition).
Having said that, I think there are a lot of people who swear by vinegar rinses. One of the main reasons we use conditioners is to increase lubricity, which reduces friction and combing forces, and I'm not sure that vinegar offers that quality, so I am a little worried about its long term use in place of conditioner. Once your hair is damaged, you can't undamage it. You can only mitigate the damage for a while.
I don't get the appeal of the vinegar rinse. I've tried it a few times, and my hair feels really awful afterwards, as if I hadn't conditioned my hair. My opinion isn't really relevant to this discussion, but I thought I'd let you know that I have personal experience with using vinegar!
I think what you found with the shampoo was an inability to lather and foam. I'm not really sure how that happened. I think it's like when you drop soap into a bathtub of bubbles - you add something to the mix that reduces foam, lather, and bubbling.
So what's the verdict? I don't really know. I couldn't find anything science-y to confirm that vinegar rinses on normal hair is effective or desirable, but I didn't find anything to say we shouldn't do it*, so if you like it and want to use it, then have at it! Just be careful you aren't damaging your hair permanently.
*Footnote: I also didn't find anything to say we shouldn't use apple sauce, grass clippings, or milk after shampooing, so my inability to find information decrying using vinegar doesn't constitute an endorsement of using it as a rinsing agent.
Thanks for the great question, Anonymous! And if you have any science-y type information on vinegar rinses, please send them along to me as I would love to learn more about this concept!