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The Sarah K So Liss BTX Volume Reduction Mask - 0% Formol - Whey Protein & Keratin - 1kg is the formaldehyde-free volume-reduction step of the So Liss line. This BTX mask is rich in Whey Protein and Keratin: it deep-conditions while it tames frizz and reduces volume, and the flat-iron seals a smooth, glossy finish. It is the gentler, formaldehyde-free route within So Liss, an alternative to the progressive keratin system for hair that needs softness and less volume rather than a full smoothing. Professional use, 1kg.
- What it is: the BTX volume-reduction mask of So Liss, formaldehyde-free (0% Formol)
- Heroes: Whey Protein and Keratin, with hydrolyzed collagen and shea butter
- What it does: reduces volume, controls frizz and adds shine
- Feel: softer, smoother, more manageable hair with a natural result
- Where it fits: used after So Liss Step 1, with a flat-iron finish
- Format: 1kg, professional use
How it works
This is a BTX-style volume-reduction mask, not a formaldehyde smoothing. It is rich in Whey Protein and Keratin, with hydrolyzed collagen, that replenish the fibre and, together with shea butter and conditioning agents, smooth the cuticle and weigh frizz down. A touch of lactic acid helps realign the hair gently, while the flat-iron at the end seals the mask into the strand for a sleeker, glossier result. Because it works through proteins and conditioning rather than formaldehyde, it carries a 0% Formol badge and gives a softer, more natural reduction in volume than a progressive keratin service.
Key ingredients
- Whey Protein and Keratin: the protein heroes, rich in amino acids that reinforce the fibre and carry the smoothing.
- Hydrolyzed collagen: replenishes protein along the strand for softness and body control.
- Shea butter and conditioning silicones: add slip, shine and manageability as volume is reduced.
- Lactic acid: a gentle acid that helps realign the hair during the service.
What to expect
After the service the hair is visibly less voluminous, with frizz calmed, more shine and an easier, smoother feel. The result is softer and more natural than a full progressive straightening: it relaxes and reduces bulk rather than poker-straightening, so movement is kept. It is not permanent and gradually eases with washing over the following weeks, and the service can be repeated. As a professional, formaldehyde-free mask, the finish depends on correct sectioning, pause time, rinsing and ironing.
How to use
For professional use, on clean hair that has been washed and dried. Divide the hair into four sections and, starting at the nape, brush the mask on strand by strand from root to ends, then comb through to distribute it evenly. Leave it on for 40 to 60 minutes. Rinse with warm or cool water until the product is removed, using water only and no shampoo. Dry the hair 100%, then flat-iron in very thin sections at 190 to 230 degrees Celsius, 7 to 10 slow passes, more at the roots and less at the ends. Use the lower end of the range on finer or lightened hair. Always do a strand test first.
Who it is for
- Stylists and salons offering a formaldehyde-free volume-reduction or BTX service.
- Frizzy, voluminous hair that needs softness and less bulk rather than a full straightening.
- Clients who want a softer, more natural result and a formaldehyde-free option.
- Coloured or lightened hair, with a strand test and the lower iron temperature.
Who it is not for
- Home users without professional training (this is a salon service with a flat-iron finish).
- Anyone with an irritated or broken scalp, and anyone sensitive to the listed preservatives or fragrance.
- Hair that fails the strand test, where the service should not proceed.
Compatibility
This mask is the BTX volume-reduction route of the So Liss system. It is used on hair prepped with the Sarah K So Liss Deep Clean Shampoo (Step 1), and it is an alternative finish to the Expert Tech Progressive System (Step 2): a formaldehyde-free volume reducer rather than a progressive keratin smoothing. It is sold within the So Liss kits, paired with the Step 1 shampoo in the Deep Clean Shampoo and BTX Mask Kit, and combined with the shampoo and Step 2 in the Complete Salon Kit.
In short
- The BTX volume-reduction mask of So Liss, formaldehyde-free with a 0% Formol badge.
- Whey Protein and Keratin plus hydrolyzed collagen and shea to reduce volume and frizz.
- A softer, more natural, formaldehyde-free alternative to the progressive keratin system.
- 1kg, professional use; after So Liss Step 1, with a flat-iron finish.
Complete your So Liss service
- Sarah K So Liss Deep Clean Shampoo Step 1 1000ml -- the Step 1 prep that cleans the hair before this mask.
- Sarah K So Liss Expert Tech Progressive System Step 2 1000ml -- the progressive keratin route, the other So Liss finish.
- Sarah K So Liss Deep Clean Shampoo & BTX Volume Reduction Mask Kit 1000ml + 1kg -- this mask paired with the Step 1 shampoo.
- Sarah K So Liss Complete Progressive Smoothing & BTX Volume Reduction Salon Kit 2x1000ml + 1kg -- the full salon kit with both routes.
Frequently asked questions
What is the So Liss BTX Volume Reduction Mask, and what does it do?
It is the formaldehyde-free volume-reduction mask of So Liss. Rich in Whey Protein and Keratin with hydrolyzed collagen, it deep-conditions while it tames frizz and reduces volume, and the flat-iron seals a smooth, glossy finish. It gives a softer, more natural result than a progressive keratin service, so the hair keeps movement while looking sleeker and shinier.
Is it formaldehyde-free?
Yes. The mask carries a '0% Formol' badge on the pack and its ingredient list contains no formaldehyde or formaldehyde-releasing preservatives. It reduces volume through proteins, conditioning agents and a gentle acid, sealed with the flat-iron, rather than through formaldehyde. As with any salon service, work in a ventilated space and follow the stated iron temperatures.
How is it applied, and at what flat-iron temperature?
On clean, washed and dried hair, brush it on in four sections from root to ends, comb through, and leave for 40 to 60 minutes. Rinse with warm or cool water using water only, no shampoo, then dry the hair fully. Flat-iron in very thin sections at 190 to 230 degrees Celsius, 7 to 10 slow passes, using the lower end of the range on finer or lightened hair.
How is it different from the Expert Tech Progressive System (Step 2)?
Both smooth, but they take different routes. This mask is a formaldehyde-free BTX volume reducer: it softens, controls frizz and reduces bulk for a natural result, with no neutralizing step. The Step 2 system is a progressive keratin smoothing that aligns the hair more strongly over repeated services. Many salons offer both and choose based on the hair and the look the client wants.
Who should not use it, and what precautions apply?
It is for professional use, on an intact scalp. It contains fragrance and the preservatives methylchloroisothiazolinone and methylisothiazolinone, which can cause sensitivity, so do a strand test and a patch test first and stop if a reaction appears. Avoid contact with the eyes and skin, do not use on an irritated scalp, and keep it out of reach of children.
How long do results last, and how do I maintain them?
The volume reduction is not permanent: it eases gradually with washing over the following weeks, and the service can be repeated to keep the effect. Maintain it with gentle, regular washing and conditioning, which helps the smooth, shiny finish last longer. A sulfate-considerate maintenance routine between salon visits is a good way to protect the result.
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Sarah K So Liss BTX Volume Reduction Mask - 0% Formol - Whey Protein & Keratin - 1kg
The BTX volume-reduction mask of So Liss: formaldehyde-free (0% Formol), with Whey Protein and Keratin to reduce volume and frizz. Professional use, after Step 1.
