Rules for Coloring Blonde Highlights to Brunette Hair

When it comes to adding a few highlights or streaks to darker hair, there are a few simple rules in terms of processing. Mostly, there are guidelines as to how much and how thick you want your highlights, as well as how bright. It's really a matter of aesthetics--or what is pleasing to you.

Streaks vs. Highlights

Most people think of any lighter sections of hair as highlights. But highlights are typically faint, very thin streaks that add a layer of sheen to the hair, only catching the light in places. Streaks are much thicker--think stripes in the hair. But many people consider both to be highlights. Both look lovely in different ways. It is all a matter of taste.
With highlights, you will probably need clips to hold back your hair so you can get at a more controlled section. Use a rat-tail comb to help you section off thin, horizontal strips of hair. Take as few hairs as possible. If you use longer horizontal stretches, you will create more of a covering sheen over your hair. If you section off thin and short horizontal stretches, you will have a smaller, scattered highlight effect. Scatter these stretches throughout your hair, using as many or as few as you wish. The more you use, the more "blond" you will get.
With streaks, you section off vertical strips of hair, creating a striped effect. You can section off wide or narrow sections to alter the thickness of the stripe. Again, as with highlighting, the quantity of streaks you use is up to you. But the more you have, the more "blond" you will be. When you scatter streaks, consider how close they will lay. Also note: the clump you gather for your streak will seem larger after it is bleached, so you might consider narrower the first time you streak your hair.

Foil vs. Plastic Cap

In actually doing the highlights (or streaks) you will need to use either foil or a plastic highlighting cap (both available from beauty supply stores). If possible, have a friend do the bleaching (or coloring) for you as she will have a better mobility in working on your hair.
To use the foil, you first fold the long edge over to make a studier edge. You (or your friend) will place this edge underneath the horizontal section of hair (or alongside a vertical section) at the root line. Using an applicator brush, you will "paint" on the bleach or blond hair coloring. Coat the hair so that the whole section is wet. Then fold the sides of the foil over and crimp it together. Now fold (semi-rolling) the bottom of the foil up until you have a tight bundle at the roots, encapsulating the hair.
A plastic highlighting cap looks like an ordinary clear shower cap, but it has pre-punched holes all over it. You can use this to create highlights or small streaks. Put the cap on and using the end of a rat-tail comb carefully pull hair through the holes. The amount you pull through will determine if you have a scattered highlight effect or small streaks. If you want highlights, pull through only a few strands. You will then cover the exposed hairs with bleach or hair color. Because of the nature of this design, your highlights may not start at the root.

Bleaching

The simplest way to achieve blond highlights is to use bleach. Bleach powder is available at beauty supply stores. All you need to go with it is some developer lift. The higher the volume number, the more lift--meaning the amount of color "lifted" from your hair. You can usually find developer in 10, 20 and 40 volume lift.
There are two factors which will determine how blond your hair becomes using bleach. The first is the lift volume and the second is time. The longer you leave on the bleach, the lighter the hair becomes. In general, 20 minutes is plenty of time. Do not leave in bleach for over 40 minutes. Remember, whether you bleach or color, you are processing your hair and any process is hard on the hair. So remember to condition your hair after you wash out the bleach.
All you do to prepare the bleach is mix the powder with your lift in a bowl and stir until it is creamy. If you are only doing a little highlighting, a tablespoon of lift and a tablespoon of powder will probably suffice. Since it is easy to mix, you can always mix more as you go.

Coloring

A more expensive way to go is to use blond hair color. Whether you buy a box (which has the developer/lift and hair color) or buy the developer and color separate, you will have some waste. Once the color is opened, it will go bad. Developer keeps, but as is often the case in boxed hair color products, the developer is either already in the hair color or does not come in a resealable container.
Using a bowl and applicator brush is still the easiest way if you are using foil. If you are using the cap method, you could just smear the hair color on. It is faster but also messier.
Follow your hair color's directions for how long to leave the color on your hair. Remember that the darker your hair, the less blond the color will be.

Helpful Hints

As most hair color products recommend, do a test patch first. For this, you select a small patch of hair, usually at the back of the neck, underneath everything to see how the product will really lighten your hair. This way, if you do not like it, the patch will not show much.
Consider how often you wish to add in highlights. While they may fade some, if you add in highlights too frequently, they will add up and overwhelm your hair, making it potentially more blond that you would like.
If you wish to color and highlight your hair, prepare your roots the desired hair color first. Then set the highlights in foil. Lastly, finish covering the rest of your hair with its new color.