Ahh a chemistry lesson thread!

- Baking soda (also bleach and ammonia) OPEN the hair cuticle, vinegar is acidic and CLOSES the cuticle
- Shampooing should be done sparingly, but at the same time you don't want dirt and styling products to build up on the hair. Leave-in conditioner can also build up if not washed out from time to time

I have heard about using baking soda, bleach and ammonia, vinegar, lemon juice, etc. on the hair, but the fact is you have to be careful what you are doing and when you are doing it. Using baking soda performs an action similar to what some of the chemicals in hair coloring, perming, and relaxer do. (not good if used incorrectly) You don't want to do something just to do it, you do something if there is a serious problem that can't be resolved in a better way. Fred would seem to have it correct with the vinegar AFTER the baking soda, since this would serve to close the cuticle.

I would just be very cautious about doing this stuff frequently, because it alters the structure of the hair. You are better off properly washing as needed, conditioning, and sealing the hair, and only resorting to using these household chemicals if there is a serious need.