Short answer: how long to leave bleach in hair depends on your hair color, texture, and the developer strength, but a common safe guideline is to keep processing times within roughly 15–30 minutes for most hair types, and up to 30–45 minutes only under careful, strand-tested conditions or professional guidance. Below is a practical overview with safety notes.
Quick guidelines
- Menial rule of thumb: 15–30 minutes for lightening with 20–30 volume developers on virgin or lightly treated hair; 30–45 minutes may be used for darker or coarser hair, but requires close monitoring and strand tests.
- Do not exceed 60 minutes in any scenario without professional supervision; extended exposure significantly increases damage risk.
- Always perform a strand test before full application to gauge how quickly your hair lightens and to check for breakage or scalp sensitivity.
- Use the lowest effective developer strength you can (e.g., 20 volume) and avoid higher volumes unless you have a trained stylist and a precise plan.
Factors that affect timing
- Hair base color: Darker hair generally requires longer processing, but this increases damage risk.
- Hair texture and thickness: Fine hair processes faster; coarse or resistant hair may take longer but is more prone to breakage.
- Previous chemical treatments: Previously dyed, bleached, or chemically treated hair can be more fragile and require shorter times.
- Desired level of lift: Lighter targets require longer processing, which raises risk.
Safety tips
- Do a strand test: Apply bleach to a small section, check progress every 5–10 minutes, and rinse when you reach the desired lightness for that strand.
- Monitor scalp reaction: If you notice burning, stinging, or itching, rinse immediately.
- Use a zone approach: Apply bleach in small sections and time each section carefully; never rely on a single global timer for all strands.
- Aftercare: Rinse thoroughly with lukewarm water, shampoo with a color-safe formula, and use a bond-building conditioner or treatment to restore moisture.
If you can share your current hair color, desired level of lift, your hair type (fine, medium, thick; virgin or previously colored), and whether you plan to use 20 or 30 volume developer, a more tailored range can be given.
