Is Bleaching Your Hair a Physical or Chemical Change? The Science of Hair Bleaching Explained

Is Bleaching Your Hair a Physical or Chemical Change?

Bleaching hair is a common practice people use to lighten their natural hair color. But what exactly happens to the hair during the bleaching process? Is bleaching hair considered a physical or chemical change?

The answer is that bleaching hair causes a chemical change to the structure of the hair. Bleach works by breaking down the melanin pigments in hair, changing the hair's color. This is a permanent chemical change, not a reversible physical change.

What Happens When You Bleach Hair

Hair is made up of a protein called keratin that contains melanin pigments. Melanin is what gives hair its natural color. There are two types of melanin:

• Eumelanin - gives hair brown and black tones
• Pheomelanin - gives hair blonde and red tones

Bleach contains an oxidizing agent, usually hydrogen peroxide. When bleach is applied to the hair, the peroxide breaks down the melanin molecules. This destroys the hair's pigmentation, making the hair lighter.

Specifically, here is what happens during the chemical reaction:

1. Hydrogen peroxide oxygenates the melanin molecule. This oxidation causes the melanin bonds to break apart.
2. The melanin breaks down into smaller particles that do not absorb light as strongly. This makes the hair appear lighter.
3. The melanin and keratin bonds in hair also break down. This causes damage to the overall hair protein structure.

Signs Bleaching Changes Hair Chemically

There are a few key signs that show bleaching causes chemical changes to the hair:

• Color change - The most obvious sign is lightening of the hair color. This shows the melanin has been chemically altered.
• Damage - Bleaching causes bonds in keratin to break, damaging the structural integrity of hair.
• Texture change - Hair can feel dry and coarse after bleaching due to protein loss.
• Faded color - Bleached hair that is re-dyed will fade faster than unbleached hair. The melanin loss remains.

Is Bleaching a Permanent Change?

The chemical changes caused by bleaching hair are permanent. The melanin in hair cannot be restored or "un-bleached" once it is broken down by hydrogen peroxide.

There are a few reasons the bleaching process cannot be reversed:

• Melanin destruction - The melanin molecules are permanently oxidized and decomposed into smaller fragments during bleaching.
• No melanin replacement - The body cannot make new melanin pigments to replace those lost in already formed hair strands.
• Hair structure - Keratin bonds are permanently broken down, leading to irreversible protein loss and damage.

For these reasons, the color-lightening effect of bleaching will remain until the hair grows out or is cut off. The hair remains permanently chemically altered.

Can Physical Changes Lighten Hair?

While bleaching causes permanent chemical changes to hair, there are some temporary physical changes that can lighten hair to a degree. However, physical changes only remove color on the surface and are reversible.

Here are some examples of physical hair lightening methods:

• Stripping color - Harsh clarifying shampoos can strip away artificial dye deposits on the outer hair cuticle. This reveals the underlying natural pigment.
• Sun exposure - The sun's UV rays can break down artificial hair pigments deposited on the surface of hair from dyes and tints.
• Mechanical abrasion - Rubbing hair with abrasive materials can wear away the outer color coating. However, it causes damage.

These physical methods only remove or wear away artificial color that coats the outside of hair. Unlike bleaching, they do not penetrate deeply into hair to alter the natural melanin.

The Difference Between Physical and Chemical Changes

To summarize, here are the key differences between physical and chemical changes in hair:

Physical Changes

• Temporary
• External
• Reversible
• Do not alter chemical structure

Chemical Changes

• Permanent
• Internal
• Irreversible
• Alter chemical structure

While physical changes only affect the surface of the hair temporarily, chemical changes cause lasting damage to the inner hair structure and melanin. This is why bleaching is considered a permanent chemical change rather than a temporary physical change.

Does Bleaching Damage Hair?

Bleaching does cause significant damage to the hair. The chemicals degrade the internal protein structure of the hair, causing both breakage and changes to the texture.

Here are some of the ways bleaching can damage hair:

• Dryness - Bleach causes hair to lose moisture, elasticity, and softness.
• Breakage - Hair becomes more prone to snapping and breaking off due to chemical damage.
• Frizz - Porosity increases, causing hair to absorb moisture unevenly and frizz.
• Loss of shine - The hair cuticle lifts and becomes rough, making hair appear dull.

For people with already dry or fragile hair, bleaching can worsen hair health and cause severe breakage. It is important to avoid over-bleaching and use repairing hair masks to counteract the chemical damage.

Preventing Hair Damage From Bleaching

While bleaching damage cannot be fully prevented, there are steps you can take to minimize the risks to your hair:

• Get professional help to avoid over-bleaching and overlap.
• Choose lower volume peroxide developer such as 10 or 20 volume.
• Space out bleaching sessions by 4-6 weeks to allow hair to recover.
• Use a deep conditioning hair mask after each bleach session.
• Avoid rubbing or brushing hair when bleached until you wash it.
• Use hair products designed for chemically treated or damaged hair.
• Trim hair regularly to remove split ends and prevent breakage.

It is also best to avoid bleaching over previously dyed hair, as the damage can be worse. If you want to bleach previously colored hair, see a professional for the safest results.

Can Bleached Hair Be Repaired?

While it is impossible to completely undo bleaching damage, the hair's protein structure can be temporarily strengthened using repairing treatments. This helps reduce and prevent breakage.

Some effective ways to repair bleached hair include:

• Protein treatments - Products with hydrolyzed keratin or collagen help fill gaps in the damaged cuticle layer.
• Deep conditioning masks - Moisturizing masks with oils, butters, or silicones can add softness and smooth the cuticle.
• OLAPLEX - This professional treatment contains a patented active ingredient that rebond broken disulfide links.
• Avoid heat styling - Limit use of hot tools like blow dryers, curling irons, and straighteners.

While these treatments can temporarily improve the appearance and feel of bleached hair, the inner protein damage remains permanent. Continued treatments are needed to keep bleached hair in optimal condition.

How Often Can You Bleach Your Hair Safely?

FAQs

Does bleaching damage your hair?

Yes, bleaching causes significant damage to the hair structure. It breaks down the proteins and leads to dryness, breakage, and loss of shine. The chemical changes weaken and alter the hair permanently.

Can you reverse hair bleaching damage?

No, the chemical changes from bleaching cannot be reversed. However, deep conditioning treatments and protein products can temporarily repair some of the damage by filling gaps and smoothing the cuticle.

Is bleached hair damaged forever?

The internal protein structure remains permanently altered after bleaching. The only way to remove the damaged parts is to grow new, unbleached hair or cut the bleached hair off.

Can you bleach over highlighted hair?

It is best to avoid bleaching previously highlighted hair, as it causes more damage. If you do bleach highlighted hair, go slowly with a professional's help to minimize breakage.

How long should you wait between bleaching?

Wait at least 4-6 weeks between bleaching sessions. This gives the hair time to partially recover and lowers the risk of excessive damage from overlapping chemical treatments.