Breaking the base is a term used in coloring hair, when you're blending the roots of the hair that are left after a highlight. Ultimately, you're trying to break up the darker color and soften the line of demarcation. Most often, breaking the base happens at the shampoo bowl after you've removed the foils, using a shade one to two levels lighter than your client's natural hair with a low-volume developer. The idea is to achieve a slight bit of lift, but without exposing the hair's underlying pigment.
Breaking the base is also sometimes called smudging, color flash, or base adjust. No matter what you call it, it’s an extremely important salon service every colorist should know how to perform. But somehow, much confusion about the technique still exists. And while the beauty of the hair industry is that there's never one single way of doing things, everyone has to start somewhere.
Breaking the base is, in essence, the process of lightening the natural new growth very quickly—by 1 to 1½ levels—to diffuse (not match) dark roots before, during, after or even in-between highlighting services. This way, the client's hair gets a rest from using lightener and there's a little more growth to work with when the time comes for a touchup highlight. The hair becomes healthier because of this, because there's little to no overlapping of lightener/bleach, which can weaken the hair over time and cause breakage. The great thing about this technique is in its speed and versatility. It can be done during a client's regular highlight appointment as an add-on to a haircut, conditioning treatment, or even blowout service.
Using a permanent lifting color mixed with 20 volume developer will generally achieve two levels of lift if allowed to process the full time (30 to 45 minutes). However, if you're trying just to break the base, you only process your formula for 10 minutes, since you only want a diffusion or softening between the client's new growth and their highlights.
While a base break can be done on any natural level, your ideal clients on which to perform this service are highlight clients with natural Levels of 6 and above. Natural Levels 1 through 5 tend to expose a lot of warmth due to the strong, red underlying pigment of those levels, which is fine for a select few, but these days, clients don't want warm hair. There's a reason so many people say things like "I don’t want to see any red.” A perfect example of when to offer the service? A client comes in for a haircut, conditioning treatment or blowout. They get highlights regularly and she's showing some new growth, but not enough to warrant bringing out the lightener. She wants her color to look fresh, but she doesn’t have a lot of time to sit for highlights. That is a great time to break the base.