* Extreme Damage: 40 volume developer is very strong. On dark hair, especially if it's already been colored or processed, it can cause severe damage, including:
* Breakage: The hair shaft can weaken and snap off.
* Extreme dryness and brittleness: Loss of natural oils and moisture.
* Elasticity Loss: Hair becomes gummy and stretches without returning to its original shape.
* Chemical Burns: The scalp can be burned by the developer.
* Unpredictable Results: Lifting very dark hair to blonde is a multi-step process. Trying to achieve it in one go with a high volume developer is unlikely to result in a clean, even blonde. You're more likely to get patchy, uneven, and brassy results.
* Scalp Sensitivity: The scalp can be highly sensitive to strong developers. Burns are a real risk.
* Professional Only: 40 volume developer is typically used by experienced professionals who understand the risks and how to mitigate them.
What *Should* You Do?
1. Consult a Professional: The safest and most effective way to lighten black hair to blonde is to consult a professional colorist. They can assess your hair's health, history, and porosity, and create a customized plan using appropriate products and techniques.
2. Gradual Lightening: Achieving blonde from black usually requires multiple lightening sessions spaced several weeks apart to minimize damage. Lower volume developers (10 or 20 volume) are typically used in these initial sessions.
3. Hair Strengthening Treatments: Your colorist will likely incorporate hair-strengthening treatments (like Olaplex or Redken's Acidic Bonding Concentrate) into the lightening process to protect and rebuild the hair.
4. Toning: After lightening, a toner is essential to neutralize unwanted brassy or yellow tones and achieve the desired blonde shade.
In short, attempting to go from black to blonde with 40 volume developer at home is a recipe for disaster. Protect your hair and scalp by seeking the expertise of a professional.