Sarah K So Liss Progressive Keratin Kit Step 1 & 2 2x1000ml

The Sarah K So Liss Progressive Keratin Kit - Step 1 & 2 - 2x1000ml pairs the two salon products behind So Liss progressive keratin smoothing: the Deep Clean Shampoo that clarifies and preps the hair, and the Expert Tech Progressive System that smooths it. Built on whey protein and keratin with a glyoxylic-acid smoothing complex, they work in sequence to calm frizz, relax the wave and leave hair sleeker and easier to style, with natural movement.

At a glance

What it is: the complete two-step progressive keratin smoothing kit
In the kit: Deep Clean Shampoo 1000ml and Expert Tech Progressive System 1000ml
Smooths with: whey protein, keratin and a glyoxylic-acid complex
Hero actives: Whey Protein, Keratin and Aloe Vera
The result: less frizz, a smoother finish and faster styling
Format: 2x1000ml, professional use
Profile: progressive keratin smoothing, not a permanent straightener

A complete two-step progressive keratin system

This kit is a progressive smoothing system, not a permanent straightener. The Deep Clean Shampoo clarifies so nothing sits between the fibre and the smoothing. The Expert Tech Progressive System is then worked through the clean hair, left to develop, rinsed and set with a flat iron: its whey protein and keratin, carried by a glyoxylic-acid complex, help the cuticle lie flatter so frizz settles. Being progressive, it eases in and wears off gradually.

What is in the kit

So Liss Deep Clean Shampoo (1000ml): a clarifying shampoo with Aloe Vera that preps the hair, so the smoothing meets a clean, even surface.
So Liss Expert Tech Progressive System (1000ml): the progressive keratin smoothing itself, worked strand by strand and sealed with heat for a smoother finish.

Key ingredients

Whey protein and keratin: the protein pairing at the heart of the smoothing, supporting the surface as heat seals in the result.
Glyoxylic-acid smoothing complex (Glyoxyloyl Carbocysteine and Glyoxyloyl Keratin Amino Acids): the smoothing chemistry that relaxes frizz without formaldehyde.
Collagen: a supporting protein that works alongside the keratin through the lengths.
Macadamia and Coconut oil with Shea butter: conditioning agents for softness and a healthy-looking shine.
Aloe Vera (in the Deep Clean Shampoo): brings a soothing balance to the clarifying prep.

What to expect

Hair looks smoother and more polished, frizz is noticeably reduced and styling is faster. Expect sleeker, more manageable hair rather than a poker-straight finish: waves relax and coarser or curlier hair becomes much smoother. The result eases off gradually rather than dropping all at once.

Who it is for

Stylists who want the complete two-step progressive keratin system in one kit.
Clients wanting less frizz and faster styling without a permanent straightener.
Most hair types wanting smoother, more manageable hair with natural movement.

Who it is not for

Anyone expecting a permanent, poker-straight result; this smooths progressively.
At-home users wanting a quick wash-in product; this is a professional applied service.
Anyone who has not done a strand test, essential on colored or lightened hair.

Professional tip

Clarify thoroughly with the Deep Clean Shampoo before you smooth, so the Expert Tech Progressive System meets a clean, even surface. Work in thin sections, keep the product off the scalp, and flat-iron in slow, even passes. On blonde, red or lightened hair, keep the iron at the lower end of the range.

How to use

Wash with the Deep Clean Shampoo to clarify and prepare the hair; on the final wash leave about 3 minutes, then rinse, and dry the hair fully.
Section the hair into four. Apply the Expert Tech Progressive System strand by strand, about 0.5 cm off the scalp, from roots to ends, then comb through.
Leave to develop for 40 minutes.
Rinse for about 5 minutes. Following the So Liss protocol, apply the neutralizing mask for 5 to 15 minutes, then rinse.
Blow-dry, then flat-iron in 7 to 10 slow passes at 190 to 230°C -- keep to a maximum of 190°C on blonde, red or lightened hair.
Wait 24 to 48 hours before the first wash.

Safety: For professional use, external use only. Always carry out a strand test first, especially on colored or lightened hair. Work in a well-ventilated area and wear gloves. Keep out of reach of children; avoid contact with the eyes and mucous membranes, and rinse well with water if contact occurs. The Expert Tech Progressive System is a glyoxylic-acid-based smoothing and there is no formaldehyde in its ingredient list. Both products are fragranced; discontinue use if sensitisation occurs.

Compatibility

The kit is the complete prep-and-smooth service on its own: clarify with the Deep Clean Shampoo, then smooth with the Expert Tech Progressive System on the clean, dried lengths, per the So Liss protocol. For a different finish, the So Liss BTX Volume Reduction Mask offers a formaldehyde-free volume-reduction route, and the complete So Liss Salon Kit brings all three together. Afterwards, a gentle, color-safe home-care routine helps the smoothness last.

In short

A professional two-step progressive keratin kit: Deep Clean Shampoo prep plus Expert Tech Progressive System.
Built on whey protein and keratin with a glyoxylic-acid smoothing complex.
A smoother, sleeker finish, less frizz and faster styling, while keeping natural movement.
2x1000ml, professional use; a progressive smoothing, not a permanent straightener.

Complete your So Liss system

Sarah K So Liss Deep Clean Shampoo - Step 1 - Aloe Vera - 1000ml -- the clarifying prep, also available on its own.
Sarah K So Liss Expert Tech Progressive System - Step 2 - Brazilian Keratin - 1000ml -- the progressive keratin smoothing, for re-ordering.
Sarah K So Liss BTX Volume Reduction Mask - Formaldehyde-Free - 1kg -- the formaldehyde-free volume-reduction route.
Sarah K So Liss Complete Progressive Smoothing & BTX Volume Reduction Salon Kit - 2x1000ml + 1kg -- all three products in one complete salon kit.

Frequently asked questions

Is the kit formaldehyde-free, and how do I use it safely?

The Expert Tech Progressive System smooths with a glyoxylic-acid complex, and there is no formaldehyde in its ingredient list, so it is not the same as a formaldehyde treatment. It is not labelled 'formaldehyde-free', so we do not make that claim. Treat it as a professional service: strand-test first, work in a ventilated space, wear gloves, and keep the product off the scalp and away from the eyes.

What is in the kit, and why use the shampoo and Step 2 together?

The kit pairs the Deep Clean Shampoo (1000ml) with the Expert Tech Progressive System (1000ml). The shampoo clarifies and opens the hair so nothing sits between the fibre and the smoothing; the progressive system is then worked in and set with heat. Used in that order, they give a more even, longer-lasting smooth result than the smoothing on its own.

Can I use it on colored or bleached hair?

It is generally used on colored and bleached hair, but porosity varies, so a strand test first is essential. Keep the flat iron to a maximum of 190 degrees on blonde, red or lightened hair, and let your stylist confirm the result on a test strand before treating the whole head. A slight change in tone is possible.

How long do the results last?

As a progressive smoothing, the result builds with each service and eases off gradually rather than dropping all at once. How long it holds depends on your hair type, how often you wash and your aftercare. A gentle, color-safe home-care routine helps the smoothness and frizz control last longer between washes.

Is this a keratin or Brazilian keratin smoothing?

Yes, it is a progressive keratin smoothing. The Expert Tech Progressive System carries the So Liss 'Brazilian Protein' seal and is built on whey protein and keratin, so it is not vegan. Rather than a one-off straightening, it relaxes frizz and smooths the hair progressively, with the result sealed in by the flat-iron pass.

Can I do this smoothing at home, or is it salon-only?

It is labelled for professional use, and the method is what makes the difference. The hair is clarified, the progressive system is applied strand by strand off the scalp, left to develop, rinsed, then dried and flat-ironed in slow, even passes at the right temperature. A stylist manages the sectioning and the heat, which keeps the result even and long-lasting.

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