Either would work. A 30 developer just processes faster. At the salon I was able to bleach my cousins deep dark hair blonde using a 20 developer, it just takes longer you just have to make sure it doesn't dry out and it should be fine. 20 developer works slower so it's easier to get an evenly bleached.
Next time, if you need to you, can always use 30 volume if you find that the 20 wasn't strong enough, but again, for most people it's plenty.
20 volume developer will lighten you natural color, but it will not make more of the dye stick, or make the finished color darker. It will make it lighter.
Using too much 20 volume developer can lead to over-processing, which means that the hair cuticles can get damaged, leaving the hair looking dull, dry, and brittle. Plus, the color won't turn out the way you want it to, and you might even end up with a funky, uneven color that looks like a tie-dye gone wrong.
30 volume developer can lift the hair by about 2–3 levels, making it a good choice for significant but not drastic lightening.
“Using different developers is key, and a HUGE pro tip to keep the red from going too dark, and old highlights from absorbing too much pigment,” explains Jill, who uses 20 volume on virgin hair, and 25 – 30 volume on previously highlighted hair. The why: Shifting developers depending on porosity is key.
20 Volume (6%) Developer
It will take you to a medium blonde hair color if your current hair color is light brown. However, this developer concentration is insufficient to turn black or dark brown hair blonde in a single bleaching process.
10 volume developers contain 3% hydrogen peroxide. These developers are also called no lift developers because they only provide moderate lift to your cuticles, i.e., lift by 1 level. This developer is perfect for when you are going to color your hair a darker color than the natural shade.
The standard developer for gray coverage is 20 Volume; however, 30 Volume and 40 Volume can also be used if the percentage of gray is low and additional lift is needed to achieve the desired result.
Hot roots happen when you apply a colour mixed with a 20 vol developer to your natural root area as this strength developer lifts the hair slightly. This is more common with lighter shades and toners.
Typically, mix 20-volume developer with bleach in a 1:2 ratio, meaning one part bleach to two parts developer for effective lightening.
Each increment of 10 represents another level of color that can be lifted. For example, a volume 10 developer will lift your hair by 1 shade, a 20-volume will lift it by 2 shades, and a 30-volume will lift it by 3-4 shades.
For instance, if you're a dark blonde and want to become a light blonde, 20 volume can help you achieve this gentle lift without needing bleach.
Vol 20 in multiple rounds: If they're worried about damage, this is the safer option, though it'll take longer to lift. Vol 30 in one go: Faster lift, but riskier for hair health. Monitor closely if used.
Use 20 Volume when lifting hair color one or two levels (levels refer to the oxidizing potential). If your hair is more that 50 percent grey, 20 Volume can help provide 100 percent coverage when used with permanent hair color.
If you're looking to maintain your natural hair color or darken it slightly, 20 volume developer is a good option. It won't lighten your hair much, but it will help the hair dye to better penetrate the hair shaft and result in longer-lasting, more vibrant color.
The choice between a 20 and 30 Volume developer hinges on your desired lift. A 20 Volume developer provides a lift of 1-2 levels, which is great for subtle changes and gray coverage. For a more significant lift of 2-3 levels, opt for a 30 Volume developer.
Use 30 Vol if you want to achieve lift without bleach.
Purple shampoos work by balancing out yellow tones, since purple and yellow are opposite on the color wheel. Blue shampoos balance orange tones because blue and orange are opposite on the color wheel.
Caramel highlights on dark brown hair can be achieved through hand-painted balayage or foils to lighten the base subtly. When the color is evenly distributed and placed in the right areas, it should mimic what the sun does naturally: give the hair a more dimensional look.
11. How long should I leave the bleach on the hair? If your client's hair is blonde (level 7 and higher) aim at between 15-20 minutes using 20 Vol developer. If your client's hair is dark blonde/light brown (level 5-6), aim at around 30 minutes using 30 Vol developer.
The developer found in box color ranges between 20 and 40 volume because that is what is needed to cover gray or to change a very dark shade. Frequently coating the hair shaft with a high volume developer will cause damage, particularly if the starting condition is weakened or fragile.