Developer is an oxidizing agent, typically a solution of hydrogen peroxide, necessary for the hair bleaching process. It activates the lightening powder, initiating a chemical reaction that opens the hair’s outer cuticle layer. Once open, the lightener penetrates the hair shaft to dissolve the natural melanin pigments, resulting in a lighter color. Choosing the correct developer volume is the most important factor for controlling the speed and intensity of this process. Selecting the wrong volume can lead to insufficient lightening or significant damage to the hair structure.
Understanding Developer Volumes and Lift
The volume number on a developer bottle correlates directly to the concentration of hydrogen peroxide, dictating its strength and potential for lift. The four standard volumes are 10, 20, 30, and 40. A 10 volume developer contains 3% hydrogen peroxide, 20 volume contains 6%, 30 volume contains 9%, and 40 volume contains 12%. This concentration determines how quickly the lightener works and how many levels of natural pigment it can remove.
The 10 volume developer is the gentlest option, offering minimal lift. It is typically used for toning pre-lightened hair or for subtle lightening on fine hair. The 20 volume developer is the most common choice, providing a moderate and controlled rate of lift. This volume is the standard for most permanent color applications and is the highest strength recommended for direct contact with the scalp.
The 30 volume developer offers a faster chemical reaction. Due to its increased strength, it is reserved for off-scalp techniques, such as foiling or balayage, where the heat from the scalp does not accelerate the process. The 40 volume developer is the strongest available, providing maximum potential for lift. However, it carries the highest risk of causing hair damage and should be used with caution. A higher volume means a faster process and greater potential for damage.
Matching Developer to Your Hair and Goal
Selecting the appropriate developer volume requires assessing three factors: the hair’s starting color, its current condition, and the intended application area.
Starting Color and Goal
For individuals with very dark hair (levels 1-4) aiming for significant lift, it is safer to use a 20 volume developer over multiple sessions. This “low and slow” approach preserves the hair’s integrity by minimizing chemical stress. Virgin hair that is coarse or resistant may require a 30 volume developer for off-scalp techniques to achieve the desired lift efficiently.
Hair Condition and Texture
The condition and texture of the hair are important considerations, as fine or previously damaged hair is more susceptible to chemical breakage. Hair that has been previously colored, chemically treated, or is naturally fine should be lightened using a lower volume, such as 10 or 20, to prevent structural damage. Using 30 or 40 volume on compromised hair can lead to immediate and severe breakage. Healthy, coarse hair may tolerate 30 volume for off-scalp applications, but constant monitoring is necessary.
Application Area
The application area is a non-negotiable factor in developer selection. The heat generated by the scalp naturally accelerates the chemical reaction. Therefore, 20 volume is the maximum strength that should ever be used for any application that touches the scalp, such as root touch-ups. Higher volumes (30 and 40) are strictly reserved for off-scalp techniques like foils or balayage, where the mixture is insulated from the scalp’s heat. Ignoring this rule increases the risk of chemical burns and severe scalp irritation.
Essential Safety and Application Tips
Proper application begins with accurately mixing the lightener and developer according to the manufacturer’s specifications. The standard ratio for most bleach powders is one part lightener to two parts developer (1:2). This creates a creamy, workable consistency that ensures even saturation. Deviating from the recommended ratio can result in a mixture that is too runny, leading to uneven lift, or too thick, preventing proper activation.
Before applying the mixture to the entire head, two preliminary tests are necessary for safety and predictability:
A patch test involves applying a small amount of the mixed product behind the ear or on the inner elbow and waiting 48 hours to check for allergic reaction or skin sensitivity.
A strand test involves applying the mixture to a small, hidden section of hair to preview the processing time and the final level of lift.
This testing helps determine if the chosen volume is appropriate and prevents unexpected color outcomes.
The developer’s chemical activity is time-sensitive and typically stops working after 45 to 60 minutes. It is important to monitor the hair visually throughout the processing time, checking the lift every 5 to 10 minutes, rather than relying solely on a timer. Once the desired pale yellow stage is reached, the lightener must be thoroughly rinsed out to halt the chemical process. A toner is typically applied afterward to neutralize unwanted yellow or brassy undertones, usually mixed with a low-volume developer, such as 10 volume.