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Hair Color Filler: Everything You Need To Know

Hair color filler is a key component in the hair dyeing process, especially if you bleach hair or considering transitioning from lighter to darker shades.

A hair color filler, commonly referred to simply as “filler,” is a product used primarily in the hair coloring process to fill in missing or depleted pigment in the hair.

As fall inches closer, the idea of switching up your summery blonde hair to a warm brunette might be tempting.

It sounds straightforward, right? Just slap on that brunette shade over your blonde, and you’re good to go. But wait—diving into the dark side directly like this can lead to some unexpected hair color surprises.

To keep you from these little hair adventures, let’s guide you about hair color fillers.

How to Know If You Need Hair Color Filler?

hair color filler for women

There’s an easy way to know if you’ll need a hair color filler when transitioning from blonde to brunette. You just have to remember the golden rule of hair color filler: If you’re going 3 or more shades darker than your hair is now, you’re going to need to fill the hair before coloring it to your desired brunette shade.

For example, if your hair is currently level 10 (the lightest blonde) and the shade of brunette you want is level 5 (medium brown), then you’ll first want to fill your hair.

What Is Hair Color Filler?

hair filler color

Hair color filler is going to be your first step in a two-step process that will take your hair from blonde to brunette and ensure beautiful results.

A hair color filler is a demi-permanent hair color that should be a shade or two lighter than the final brunette color you’ve decided on and contain warm tones (usually oranges and/or reds). 

Hair color filler is used to add back in the warm pigments (also called re-pigmenting), which were removed from the hair when it was lightened to blonde. You might also be a natural light blonde who never had these pigments in her hair to begin with!

When we lift the hair from dark to light, we are lifting through and removing red and orange pigment from each strand.

That’s how we get blonde with pale yellow undertones without an orange or red tone in sight. Removing these pigments is what gives you beautiful blonde hair free of brass.

However, when you’re doing the opposite of blonding, aka coloring back to a darker shade,  you’re going to need to add these pigments back into the hair.

Without these pigments, your new brunette hair may come out patchy and uneven and the overall color can lack depth and appear “muddy”. A hair filler will also prevent fading, you can think of it as an extra layer of protection.

How to Choose the Right Hair Color Filler

To ensure that your hair color filler is going to get you the rich, long-lasting brunette hair you crave,.’, make sure you choose the right shade of hair color for your filler. 

We’re going to give you a few examples of what color we would choose for our hair color filler in different blonde to brunette scenarios:

Scenario #1: Platinum Blonde (level 10) to Medium Brunette (level 4) 

platinum blonde to medium brown hair color filler

In this case, you’d be darkening your hair 6 levels so you’re 100% going to need hair color filler. Since you’re starting out platinum blonde, your hair will be missing the yellow, orange, and red tones that a level 4 would contain. Hair color filler should be 1 to 2 shades lighter than your desired hair color. 

For this, we would choose a level 6 (two shades lighter than your final color), and we would choose a shade that contains copper (orange and red) and gold (yellow). Look for shades in a level 6 with the letters G(gold) and C (copper). 

Your final formula for hair color filler would look something like this: 6CG with a 5 or 10-volume developer.

Scenario #2: Medium Blonde (level 7) to Dark Brunette (level 3)

medium blonde ro dark brown hair color filler

This time you’d be deepening the hair 4 levels, so again, you’ll definitely need hair color filler. Starting out at level 7 means that hair is missing red and orange pigments that would be found at level 3.

Look for shades in a level 5 with red and copper. You’ll want to look for shades in level 5 with the letters R (red) and C (copper).

Your final formula for hair color filler would look something like this: 5CR with 5 or 10-volume developer

Pro tip: Only use demi-permanent hair color with a 5 or 10-volume developer, you won’t need anything higher than that because you are just depositing hair color and not lifting the hair lighter. 

How to Apply Hair Color Filler?

Hair color filler is easy to apply and only needs to cover your blonde hair so you can skip any outgrowth at the root you may have.

If the demi-permanent hair color being used is in a cream form you can apply the color with a bowl and brush, making sure to saturate each section of hair. If you ever applied a root-to-end hair color before, you’re already going to be a pro at this! 

If you have a gel or liquid demi-permanent, you can apply it with a toner bottle, again making sure that every section is fully saturated and you haven’t missed any areas of blonde. 

You’ll then let the hair color filler process for 20 minutes. After the processing time is up, rinse thoroughly and shampoo and condition. After the filler is rinsed, you’ll blow dry your hair until it’s 100% dry. 

We want to warn you that you might be shocked by what you see after you dry your hair.

Your hair may look orange or red after this step but keep in mind this is exactly what you want the hair color filler to look like. The second step will turn you into a beautiful brunette! 

Next, is the second and final process which is applying your permanent brunette hair color from root to end. Saturation is key so make sure to take your time applying the hair color to each section.

You’ll process for the recommended processing time (usually 30 minutes) and then rinse, shampoo and condition, and blow dry.

Your rich, gorgeous brunette hair color will be revealed, and you’ll be glad you did the hair color filler! 

Pro tip: If any of this sounds confusing, keep in mind you can always see your hair stylist for big hair color changes. Hair stylists are highly trained in hair color fillers and can help you to achieve your brunette dreams! 

Key Things To Remember: 

  • Hair color filler is used to add depth and warm tones back into blonde hair so that your brunette hair looks warm, even, and rich. Without hair color filler, dark hair color can become uneven and look “muddy”. If you’re going more than 3 shades darker than your starting hair color, you’ll need a hair color filler.
  • Hair color filler is applied before your final hair color.
  • To find the right shade of hair color filler, you’ll want to find a demi-permanent shade that is 1 to 2 shades lighter than the final shade of brunette. 

We wish you all the best in your blonde-to-brunette journey! We hope that after learning all about hair color fillers, you feel confident not only in changing your hair color to something completely new but also in knowing how to do it properly to get the best results!