Here's a breakdown:
* Immediately after washing: The scalp and hair are stripped of their natural oils. This is why hair can feel dry and squeaky clean.
* 12-24 hours after washing: The scalp begins to produce sebum (natural oil). This oil starts to travel down the hair shaft.
* 24-72 hours (or longer): The time it takes for the sebum to distribute enough to make hair look or feel oily depends on several factors:
* Hair type: Fine hair tends to get oily faster than thick or coarse hair because the oil has less surface area to cover.
* Scalp oil production: Some people naturally produce more oil than others.
* Hair porosity: High porosity hair absorbs oil more quickly, while low porosity hair can cause oil to sit on the surface.
* Hair length: Longer hair takes longer for the oil to travel down the entire length.
* Activities: Exercise, wearing hats, and touching your hair can all contribute to oil build-up.
* Products used: Some hair products can add to oiliness, while others can help absorb it.
In summary: There's no specific time when hair starts "cleaning itself." It's more about the gradual accumulation and distribution of natural oils from the scalp. For most people, the effects of this process become noticeable within 1 to 3 days after washing.