I agree with the bold
SongbirdB, I suggest that you clarify your hair and make sure your hair is clean and product free (no serums, no protein conditioner!), and then try the porosity test. If the hair still takes more than 2-3 min to sink or it doesn't sink, then you make want to look into changing your shampoo for a while. Because you hair is not taking in any moisture at all, I suspect that you hair's pH is either 4.5 or lower, which can happen sometimes.
Conditioning shampoos that have cationic conditioners (such as Motions Lavish or Keracare Hydrating/Detangling) generally have a higher pH (5-6) and will help to open then cuticle layers up. But you have to realize that this may take a few washes before you'll correct it, so have patience.
If I remember correctly, you and I discussed on Fotki that we might be hair twins, so I want to confirm that you have fine textured strands, right? If so, then this won't take as long as you think; fine hair generally doesn't have many cuticle layers.
When you go to rinse your hair well prior to your shampoo, how long does it take for your hair to get saturated with the water? Being aware of the time it takes now can help determine if the porosity issue corrects itself later. So if after switching shampoos and/or doing a corrective treatment, you notice your hair takes less time to get wet in the shower, then you are on the right track
I also wanted to add that those who want to try the color treatment to help open the cuticle layers should really try changing shampoos first, just because some people will have better results than others, not to mention the fact that haircoloring is a chemical services, and there are other factors that come into play to make this a viable option to correct porosity. If you are unsure just ask one of the knowledgeable ladies on this board (like
Gymfreak lol!)
Oh, and as far as the ACV rinse...if you have seemingly stalwart strands, ACV's not gonna help. ACV rinses are meant to lightly seal the cuticle, which is the opposite effect we are going for. Products that are slightly more basic than the hair are necessary for hair that is naturally lower in pH.
ACV only modifies the pH a little. So if you condition the hair, which has a natural pH somewhere around 4.5-5.5, with a pH balanced conditioner and then rinse with water (pH 7), the hair's going to go up a bit. ACV will bring it back to the normal range. Any drastic changes that need to be made will come from a stronger product. I know Porosity Control conditioner is often mentioned, but it has it's place too, and cannot always solve the problem. But for simple issues, it is great