How long does a keratin treatment last?

Most keratin and smoothing treatments last three to five months. The range depends on how often you wash, whether you use sulphate-free products, your hair's natural texture and how much you swim. Treatments fade gradually rather than growing out in a hard line, so hair returns to its natural texture over time instead of showing a demarcation.

Will a keratin treatment make my hair completely straight?

No, and that is the point. A keratin or smoothing treatment is not a chemical relaxer. It reduces frizz, loosens the curl pattern and dramatically cuts blow-dry time, but it leaves movement in the hair. Curly hair typically becomes a looser, more defined wave rather than poker straight. If you want your natural texture preserved but manageable, that is the intended outcome.

How much does a keratin treatment cost in Boston?

In the Boston market, express or partial smoothing treatments generally start around $220, while full keratin services commonly run $420 or more. Price tracks hair length, density and how much product the head takes, so it is confirmed at consultation.

Can I get keratin if my hair is coloured or highlighted?

Yes. Keratin and colour work well together, and smoothing often makes coloured hair look glossier because a flatter cuticle reflects more light. Sequencing matters: colour is normally done first, in the same appointment or shortly before, since the smoothing process can slightly lighten tone. Discuss both services at consultation so they can be planned in the right order.

What do I have to do after a keratin treatment?

Aftercare is what determines how long the result holds. Switch permanently to sulphate-free and sodium-chloride-free shampoo, avoid salt water and heavily chlorinated pools where you can, and rinse promptly when you do swim. Depending on the specific system used, there may also be a short waiting period before the first wash — you will be told exactly what applies to your treatment.

Keratin & Smoothing Treatments in Boston

What a smoothing treatment does

Frizz is a cuticle problem. When the outer layer of the hair lifts, moisture moves in and out freely and the strand swells unevenly — which is why hair behaves one way indoors and another the moment you step outside in July. A keratin or smoothing treatment coats and seals that cuticle with protein, then sets it with heat.

The practical effects are consistent:

Frizz drops sharply, including in humidity.
Blow-dry time is cut significantly — for many clients this is the real selling point, worth twenty minutes back every morning.
Curl loosens into a softer, more defined pattern rather than disappearing.
Hair reads glossier, because a flat cuticle reflects light evenly.
Styling holds longer between washes.

What it is not: a relaxer. Chemical relaxers permanently break and reform the bonds that give hair its curl. Smoothing treatments coat and seal, then fade gradually. Your natural texture comes back — no line, no regrowth stripe, no commitment you cannot reverse by waiting.

Who it suits

Smoothing is worth considering if you recognise yourself in any of these:

You blow-dry your hair straight and humidity undoes it within an hour.
Your routine takes more than thirty minutes and you would like it back.
You have a loose wave or curl you like in principle but cannot get to behave.
Your hair is coarse or dense and simply takes a long time to dry.
You are heading into wedding season, or a summer of harbour humidity, and want one less variable.

It suits fine, limp hair less well — smoothing can flatten what little volume is there. That is a consultation conversation, and sometimes the honest answer is a deep conditioning treatment rather than a full smoothing service.

The appointment

Expect two to three hours for a full treatment, less for an express service. The sequence is a clarifying wash to strip build-up and open the cuticle, a careful sectioned application, processing time, then blow-drying and flat-ironing in thin passes to seal the product in. The flat-iron stage is slow and it is the part that determines the result.

If you are colouring as well, colour usually comes first — smoothing can shift tone slightly, so it is better to smooth over finished colour than to colour over a fresh treatment. Book both together and the order gets planned for you.

What it costs

In the Boston market, express and partial smoothing treatments generally start around $220, and full keratin services commonly run $420 or more. The variables are hair length, density and how much product the head actually takes. S.A.S Salon confirms pricing at consultation.

Making it last

Sulphate-free, sodium-chloride-free shampoo — permanently. Salt and sulphates strip the treatment faster than anything else. This is not optional.
Wash less often. Every wash costs you some longevity.
Rinse after swimming. Chlorine and salt water are both hard on smoothed hair.
Follow the initial waiting period if the system used calls for one — you will be told exactly what applies.

Questions we get asked

How long does it last?

Three to five months for most people, depending on wash frequency, products, natural texture and swimming. It fades gradually rather than growing out in a line.

Will my hair be completely straight?

No. Smoothing is not a relaxer. It cuts frizz, loosens curl and speeds up drying while leaving movement. Curly hair usually becomes a looser, more defined wave.

How much does keratin cost in Boston?

Express and partial treatments generally start around $220; full keratin services commonly run $420 or more, depending on length and density.

Can I get it on coloured hair?

Yes, and it often makes colour look glossier. Colour is normally done first, since smoothing can shift tone slightly. Book both together so the order is planned.

What aftercare is required?

Sulphate-free and sodium-chloride-free shampoo permanently, fewer washes, and a rinse after swimming. Some systems also call for a short wait before the first wash.

Book a treatment consultation

S.A.S Salon is by appointment only. Call or text (786) 797-0663, message on WhatsApp, or use the contact form. Planning colour as well? See balayage & highlights.

Keratin & smoothing, built for this climate