FWIW- My best friend is a master spinner, weaver and dyer. She also makes their soap.
I am a baby at all this, though middle-aged.
When I was having problems with my first shampoo bar results on my hair, I went to her for help. She was most concerned on the ACV formula, knowing how it works with protein fibers (human hair is technically a protein fiber). She said the common recipe for the ACV mixture is usually made too strong. 2 tbsp. to a 16 oz empty bottle and topped with water is normally strong enough.
Also, when one lives in hard water areas like we do, the ACV can either leave the hair gummy, greasy and/or fly-away if used after washing one's hair with a shampoo bar (though some do not have this problem). I tried her suggestion of not using the ACV mixture more than once a week, and
*before* washing my hair. I squirted a little on, washed up, rinsed out the ACV and then finished up by washing my hair with a shampoo bar. It worked! No more gummy, greasy hair that had static-cling of the worst sort. My hair felt almost dry and squeaky when rinsing, though the soap washed out well, unlike before when I used the ACV rinse afterwards. I feared I would never get my comb through my mass of hair after getting dressed. My comb glided through my hair, even the fine-toothed wooden one.
I have thick, oily hair and scalp. I have always lived in hard water areas (forest/mountains). I tried for years to wash my hair very little on the common theory that it makes your hair less oily. For me, it is wrong. After months of trying to wash once a week or so, I gave up and stayed with at least every other day. We are all different, that is for sure.