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Does Leaving Hair Dye in Longer Make It Darker? 


Are you someone who uses hair dye and you’ve been wondering if it’s helpful to leave the hair dye in longer than the recommended time? Maybe you’ve just dipped your toes into coloring your hair and you want to learn more.

We put together a guide here that will help you understand what hair dye does to your hair and what happens if you use it in different ways, like leaving it in for a long time.

What Happens If You Leave Hair Dye in Longer Than Recommended?

You probably came here for the answer to this question, so let’s get it out of the way first.

Does leaving dye in longer make it darker? It’s recommended that you leave hair dye in for about 30 to 45 minutes. You want to follow the directions as best as you can, because going beyond the directions and doing things your own way can give you a hair color you’re not really happy with. Make sure you’re following the usage instructions precisely, because some hair dyes are different from others.

You may need to leave your hair dye in for longer, depending on the kind of hair you have, and we’ll talk about some of the factors that affect how a hair dye works in just a moment. Before that, let’s answer the question of what would happen if you left hair dye in for longer than you’re supposed to.

Typically, what happens is that your hair becomes a shade or two darker than it’s supposed to be. Leaving the hair dye in for longer allows the dye to set and create a stronger effect.

You do want to be careful about how long you leave the dye in, because it can really darken your hair more than you might expect it to. It’s always safer to follow the directions and see how your hair looks after you’ve left the dye in just the appropriate amount of time.

From there, you can decide if you need to do more, dyeing your hair further or leaving it alone.

What Are the Hair Dye Factors You Should Know?

There are a few different characteristics of your hair that will affect how hair dye reacts with your hair. You may need to shorten or lengthen the amount of time you leave dye in or use more dye because of the kind of hair you have.

The dye product should have instructions on it and the expected result you get from using it. It may also have indications for what to do if you have a certain type of hair and how to use the dye depending on the different factors we’re going to talk about.


Thick hair will take the longest amount of time to dye. You will need to leave the color in for longer, and you shouldn’t expect significant results if you leave dye in your thick hair for the same amount of time as you would leave it in for thin hair.

If the dye manufacturers recommend that you leave the dye in for 30 to 45 minutes, you use the low end of that range for thin hair. The medium range- around 40 minutes- would be ideal for medium thickness hair, while the higher end of the range- 45 minutes- should work for thick hair.


Did you know that the color of your hair affects how long do you need to leave the dye in for? If your hair is black, you’ll need to leave the dye in for longer, as there’s more melanin for the dye to work through and counteract. Lighter hair can be dyed quicker, so you won’t need to leave the dye in for as long.


This can be a tricky factor to take into account, but how porous your hair is will affect how quickly the dye is able to penetrate it. You can have a high porosity or low porosity, and you can determine how porous your hair is by putting several strands of hair in some water.

If it takes less than five minutes for your hair to sink into a cup of water, then you have hair that is very porous. If after five minutes, your hair is still floating in the water, you have a low hair porosity. That low porosity means that your hair will take longer to dye, as it will resist the dyeing process.

How Does Hair Dye Work?

Hair dye is designed to change the color of your hair, moving it to a darker or different shade. If you wanted to lighten your hair, you will use hair bleach, but dyeing your hair gives it a different shade.

Hair dye will affect and change the color of your hair, and different kinds of dye work in different ways. Semi-permanent hair dye does not penetrate all the way through your hair, so the color change doesn’t last as long. Permanent hair dye penetrates all the way through your hair follicles and contains strong chemicals.

Leaving those strong chemicals in for too long can damage your hair and affect how fragile or strong it is. It can also make your hair harder to change back to its original color or to dye a new color.

That may leave you wondering- can you leave semi-permanent dye on longer? This kind of dye is not going to have as dramatic an effect on your hair color over the long term, nor will it affect your hair strength, density, and health as much as permanent hair dye would.

In other words, there’s less risk of leaving semi-permanent hair dye in for a long time compared to permanent hair dye. Still, it’s best to follow the packaging directions and not overdo it, if possible.

You may want a more permanent hair color but not want to take the risk of using permanent hair dye. If you’re wondering if it’s safer and wiser to leave semi-permanent hair dye in for a long time and try to get a more permanent color, you can, but it is still not advisable.

Can You Leave Semi Permanent Dye on All Night?

You could leave semi-permanent hair dye in for a long time and not suffer any effects. Because it is depositing the hair color rather than bleaching your hair or truly changing the hair color, it’s much safer to leave that semi-permanent hair dye in all night.

You probably won’t have a permanent change of hair with this hair dye. That’s not really a risk, and it will leave you with truly changed hair color for longer. It can give you a more permanent effect that’s still just as easy to get rid of as it normally would be when using semi-permanent hair dye.

The danger with this dye, though, is that it often acts as a conditioner. What that does is thicken and fill out your hair as it hydrates, and then that dries out. This happens a few times during the night, and it can be unhealthy for your hair.

It may not harm your hair if you do it a couple times a year, but if it’s something you do frequently and regularly, your hair will become permanently damaged.

What to Avoid When Coloring Your Hair

We want to leave you with a few tips to keep in mind when you’re coloring your hair.

1. Use a Professional Hair Colorist

First of all, it’s better to go to a professional stylist the first time you color your hair. You’ll get expert advice on how the dye affects your hair type. You’ll also learn the process you need to go through to dye your hair yourself, so you can do follow-up colorings yourself, if you like.

2. Bleaching Your Hair

You shouldn’t bleach your hair and then try coloring it shortly afterwards. You need to give your hair time to recuperate from the bleaching process, as it does weaken your hair follicles.

3. Cheap Hair Products

Try to avoid using low quality dyeing treatments. Some of these contain harmful chemicals that can damage your hair or that may not give you the color you want. If you’ve never used a particular brand before, you may want to look up reviews and find out what other people’s experiences with it have been.

4. Don’t Over Wash

Don’t wash your hair too soon after you dye it. You could wash out the dye, particularly if you put in semi-permanent hair dye. You should wait at least 24 hours after dyeing your hair to wash and shampoo it. This allows the dye some time to set properly.

Finally, we want to reiterate that it’s not a good idea to leave the hair dye in for too long, particularly with permanent hair dye. Read and follow the instructions on the dye product packaging and follow those very closely. If you keep to the directions, you shouldn’t have any issues with hair dye darkening your hair too much or damaging your hair.

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