You’ve just had your hair coloured-maybe a stunning balayage, a bold red, or that perfect icy blonde. Now, you want to keep that colour as fresh and vibrant as possible, all while switching to a more sustainable hair routine. With solid shampoo bars trending, the big question is: are they safe for your colour-treated hair?
As a stylist who has spent two decades behind the chair, I can tell you that caring for coloured hair is about more than just skipping sulfates or choosing something labeled “gentle.” The real keys to maintaining vibrant, healthy colour go much deeper. It all comes down to the overlooked science of pH balance, the right type of protein, and minimizing friction-three factors that will make or break your results with a solid shampoo bar.
Why pH Balance Is Everything
Think of hair like a delicate fabric. Its outer cuticle layer opens and closes depending on what you use to wash it. If your shampoo is alkaline (with a high pH), those cuticles open-letting your expensive colour molecules slip away. The goal is to keep your hair wash routine in the sweet spot: a pH of 3.5-6.5. This keeps your strands smooth and locks in colour far longer.
Unfortunately, many “natural” shampoo bars are really just soap in disguise. These have a high pH, which is bad news for colour. The smarter choice is a bar formulated with syndet cleansers-ingredients like sodium cocoyl isethionate, which are pH balanced and gentle for colour-treated hair. Brands like Viori have nailed this, ensuring the bar doesn’t strip or fade your shade.
The Right Protein Makes All The Difference
Protein in haircare can be a blessing or a curse. When done right-including hydrolyzed plant proteins in a solid bar-it helps reinforce fragile hair, fortify those cuticle gaps, and prevent colour leaching. But too much or the wrong type of protein can make hair brittle and even speed up fading.
What you want for coloured hair is a balanced approach using hydrolyzed (that means “broken down and small enough to actually get into the hair”) proteins. In the right dose, these strengthen your hair after colouring, without causing stiffness or buildup. The result? Shinier, healthier hair and longer-lasting colour.
Friction: The Hidden Threat To Salon Colour
Let’s be real-most people use solid shampoo bars by rubbing them right onto their hair. But this can create friction, especially on delicate, colour-treated hair, lifting the cuticle and encouraging colour loss.
Here’s the pro technique:
- Lather the bar between your hands to create a rich foam.
- Apply the lather gently to your scalp and hair, using your fingertips-not the bar itself.
- Rinse with cool or lukewarm water to help seal the cuticle.
This simple switch can help preserve your beautiful colour for weeks longer between services.
Bonus: Smart Conditioning Without Silicones
Modern solid bars take colour care further by adding gentle plant-based conditioners. Look for ingredients like behentrimonium methosulfate-which isn’t a sulfate at all, but a natural detangler and softener. Combined with nourishing butters and oils, these bars give your hair slip, shine, and extra protection without the heavy buildup silicone-based products can leave behind.
Is Your Shampoo Bar Up to the Task?
Before you commit, ask these stylist-approved questions:
- Is the bar pH-balanced (between 3.5-6.5)?
- Does it use syndet-based cleansers-not saponified oils or “soap”?
- Is protein hydrolyzed, and are plant butters/oils included?
- Does the brand recommend lathering in your hands, not direct bar-to-hair?
If you can answer “yes” to all of these, you’re holding the best type of solid shampoo for colour-treated hair.
Stylist Tips for Making Your Colour Last
- Use cool water for rinsing-heat raises the cuticle and can dull your colour.
- Try a diluted apple cider vinegar rinse every few weeks for extra cuticle-sealing benefits.
- If you use a solid conditioner, let it sit for a few minutes as a deep treatment, or apply a tiny bit just to your ends as a leave-in for added polish.
- For especially damaged or porous hair, rotate in a clarifying shampoo once a month-just at the scalp-to prevent buildup.
The Takeaway
The best solid shampoo for coloured hair is about more than just skipping harsh ingredients. It’s about understanding the science of hair: maintaining an optimal pH, using the right (not too much) protein, and respecting your cuticle with the correct application method. If your shampoo bar passes these tests, you can expect gorgeous, vibrant colour-no plastic bottle needed.
Ready for longer-lasting results from your next colour appointment? Take a closer look at your solid shampoo bar, make a few tweaks to your routine, and enjoy hair that wows from root to tip-between every visit.