Keratin treatment with hair extensions: what needs checking

A keratin treatment with hair extensions needs an individual plan; I would not approve it from “human hair” or “tape-ins” alone. I treat your own hair. We must decide whether the extensions come out first (my preference for Straightment DEMI) or stay in (nothing guaranteed, £100 added), then check the exact extension and attachment requirements. If those details are missing, the treatment decision waits.

I offer work on hair with extensions only to my Loyal Clients. My preferred treatment for a client with extensions is a keratin treatment, Straightment DEMI.

How I work with extensions

I offer work on hair with extensions only to my Loyal Clients.

My preferred treatment for a client with extensions is a keratin treatment, Straightment DEMI. On hair with extensions, a perm is also possible, but it is long, costly and tested first. I would not usually do Permanent straightening on hair with extensions.

Straightment DEMI

1. Take the extensions out before your appointment.
2. They can go back in 3 days after the treatment.

If the extensions are left in

• Nothing is guaranteed.
• £100 is added to your bill for the extra time, once I have assessed the hair. That is not an automatic booking option.
• “Nothing is guaranteed” is about the cosmetic result. It does not remove my duty to do the work with reasonable care and skill, or your legal rights (GOV.UK).

Whatever we choose

• There is no guarantee on previously treated hair.
• You will most likely need a colour update afterwards.

Why it is difficult to work on hair with extensions left in

1. The product has to stay away from the bond. One trade protocol for clients already wearing extensions applies the smoothing solution and the flat iron a quarter to half an inch away from the bond, to avoid slippage (Behind the Chair, updated 2017). The hair next to the bond is then left out, so the finish can look uneven. (The uneven finish is my reasoning, not the source’s.)
2. Bonds and tapes dislike products. Extension makers tell you to keep conditioner and oil off the bond or tape, because it can slip (Cliphair, Great Lengths).
3. Chemicals can break down tape adhesive. Colour is the example one brand gives (Donna Bella, 2018).
4. Heat has limits. Brands cap styling heat on extensions at about 180°C (Remi Cachet).
5. The extension hair may not take the treatment. One extension retailer says a Brazilian blow dry belongs on your own hair, not the extensions (Cliphair, 2025). Some makers rule out chemical treatment altogether.

What you will read elsewhere

• Keratin first, extensions after: Cliphair says to have the treatment before installing.
• Waiting before refitting: one trade article says one week or three washes (Behind the Chair, 2017). My 3 days is my own salon rule, not a figure from a study.
• Washing after keratin on natural hair: UK salons quoted anywhere from 30 minutes to 72 hours (HJI, 2018). Mine is my own rule: same day for Semi and Demi, 48 hours after Permanent, Cold and Hot.

My view: identify what you want to change

When you say “my extensions are frizzy”, I want to see which hair you mean. Is your own hair expanding above a smooth extension length? Are the added lengths changing while your own hair stays smooth? Or is an attachment slipping and making the shape uneven?

Those are different consultations. I do not choose a smoothing service simply because two textures are visible. A better texture match, a different wearing plan or a maintenance assessment may be more appropriate than another chemical process.

Start with extension fibres and attachments if you do not know what is fitted. For a visual mismatch, the separate blending article explains how to describe the problem clearly.

Semi, Demi and Brazilian are not interchangeable instructions

Straightment Semi and Straightment Demi are my named services. “Brazilian blow dry” and “keratin treatment” are also used in search and conversation, but I need the actual service name and previous treatment record before using either as a description of what is on your hair.

My rules allow same-day washing after Semi and Demi. That tells you about those treatments on suitable hair; it does not override a new attachment’s washing restriction or prove that its lengths can receive the formula.

For another salon’s system, follow that system’s instructions. I will not apply my wash timing to an unidentified Brazilian treatment. Likewise, I do not use a general claim about “keratin” to promise attachment compatibility.

Decide the plan

1. Tell me whether extensions are already fitted.
2. Show me the exact attachment and the extension care information.
3. Point to your own hair that you want smoother.
4. Agree whether the extensions come out beforehand (preferred) or stay in, with the terms above.

This is my planning method, not a suggestion to isolate rows yourself. Hiding a section does not give us enough information to approve the appointment.

Plan the order before booking

My starting preference is to settle the intended result for your own hair before final extension matching and fitting, when that is practical. It lets the extension decision respond to the hair you actually intend to wear. For Straightment DEMI the rule is fixed: extensions out before, back in 3 days after.

There is no automatic “extensions tomorrow” rule. The treatment first-wash restriction, the fitter’s preparation requirements and the actual attachment instructions all have to work together. A manufacturer, for example, warns against conditioners and styling residue before its application. source

Where an existing installation prevents a suitable assessment or service plan, discuss professional removal and reassessment with the relevant practitioner. Do not pull tapes apart or heat a bond to make space.

Do not promise to smooth unknown extension hair

Some extension manufacturers prohibit chemical alteration of their own hair. source That is enough to reject a blanket “all human hair can have keratin” promise. A sample test does not cancel a manufacturer’s prohibition.

If the supplier does permit a proposed process, I still want its written instructions, the exact product history and an appropriate professional assessment. Approval to colour is not automatically approval to smooth; approval for the loose lengths is not automatically approval for the fitted attachment.

If the only evidence is “my friend did it”, I have no usable compatibility record. I would discuss alternatives rather than turn your fitted hair into a trial.

Your checklist

• Exact previous and planned smoothing service.
• Fibre, supplier, shade and processing history.
• Attachment system and fitting or maintenance record.
• Whether the extensions will be out or left in.
• First-wash and fitting requirements agreed together.
• Colour plan: my Demi rule puts colour afterwards, with suitability assessed.
• A named contact if anything slips or feels uncomfortable.

Afterwards, use the two-zone aftercare routine. If tapes have already moved, use damage and slippage assessment before adding products or booking more smoothing.

Questions

Can a Brazilian blow dry make tape-ins slip?

A slipping installation needs its own assessment; the sequence alone does not prove the cause. Record the service, products and timing, then contact the fitter. Do not glue the tapes back yourself.

Does a keratin bond mean keratin treatment is safe?

No. The attachment name does not establish chemical compatibility. They are separate parts of the consultation.

How long must I wait before fitting extensions?

For Straightment DEMI: take the extensions out before your appointment, and they can go back in 3 days after the treatment. If they are left in, nothing is guaranteed and £100 is added to your bill for the extra time. For another treatment, or keratin from another salon, we agree the interval after assessment, never shorter than the treatment’s first-wash restriction and always allowing for the attachment’s requirements.

Sources

• remicachet.com
• remicachet.com