In 1909 a Danish chemist named Søren Sørensen, who ran the chemistry department at the Carlsberg brewery laboratory in Copenhagen, gave the world the pH scale. He was studying proteins and needed a plain way to say how acidic a liquid was. Brewers took it up first. A century later it is the quiet number behind a lot of what is printed on a bottle in the shower.

 

Redken shampoo starts from that number. In 1960 an actress named Paula Kent, who had baby-fine hair, sensitive skin and allergic reactions to the salon products she was handed, teamed up with a hairdresser and chemist named Jheri Redding. The name is a mashup, Red from Redding and Ken from Kent, and she paid for the launch with what she earned from a Hamm's beer commercial. Redken's own account says the first products were built on three ideas: protein, an acidic pH of 4.5 to 5.5 to sit alongside hair and skin, and distribution through licensed cosmetologists. L'Oréal's U.S. arm bought the company in 1993, and the brand still carries 5th Avenue NYC on its labels.

 

I like a brand that began with one person's annoying problem. The trick is to sort the line by what your hair needs and ignore the bottle you like the look of. The first grid is the core lineup. Acidic Bonding Concentrate is the one Redken says runs on citric acid, not protein. Extreme is what the brand calls the Protein Expert, and the Extreme Length version is for hair you are trying to grow out. All Soft is for dry, brittle hair, a moisture job rather than a repair job. Acidic Color Gloss and Color Extend Magnetics are the color-treated pair, both sulfate-free, Frizz Dismiss is the humidity fighter, and Volume Injection is for hair that lies flat by noon.

Start with a job description. Write down the one thing your hair does that annoys you most, brass, frizz, flakes, buildup or thinning, and choose the shampoo built for that and nothing else. The second grid is where the specialists live.

 

Blondage Color Depositing Purple Shampoo is the toner for blonde hair that has turned warm, and the set with the conditioner and Express Anti-Brass Mask is the version to pick if you would rather do the whole routine in one go. All Soft Mega Curls is built for curl pattern, and Acidic Bonding Curls Silicone-Free Shampoo is the one for curls that have also been colored or heat styled. Acidic Grow Full System Densifying Shampoo is aimed at thinning strands, and it is worth remembering that a shampoo can only work with what is on the scalp, so patience matters more than the bottle.

 

Scalp Relief Dandruff Control and Hair Cleansing Cream Clarifying are the reset buttons. A pairing I like: clarify once every couple of weeks, then use your regular shampoo, so buildup never gets the chance to make good products look bad.

 

The Acidic Bonding Concentrate refill pouch is the small, sensible one here. It means fewer bottles arriving at your door.

 

What I would skip: purple shampoo on hair that is not blonde or lightened. It has nothing to tone, and it is easy to overdo.

One rule for a shampoo line: finish what it starts. A shampoo sets the direction, and the conditioner is where the formula either carries on or quietly gets undone. That is why I like buying these in pairs.

 

Acidic Bonding Concentrate Conditioner and Acidic Color Gloss Conditioner follow their shampoos, and they are the ones I would reach for on hair that has been lightened or colored. All Soft Conditioner keeps the moisture going for dry, brittle hair. Extreme Conditioner and Extreme Length Conditioner belong to the protein side, so they suit hair that snaps when you brush it. Frizz Dismiss Sulfate-Free Conditioner and Volume Injection Conditioner mirror their shampoos, which is exactly the point.

 

Four more join them for the specialist shampoos above: Color Extend Magnetics Conditioner finishes the color-treated pair, and the Acidic Grow Full System Densifying, All Soft Mega Curls and Acidic Bonding Curls Silicone-Free conditioners each follow the shampoo they match.

 

Blondage Color Depositing Purple Conditioner is the gentle top-up for a blonde who does not want to shampoo with purple every wash. Use it once a week, leave it on a little longer than you think, and rinse.

 

A habit worth borrowing from the salon: apply conditioner from mid-length to ends, comb it through, and give it a minute while you wash your face. The comb does more of the work than the formula.

 

What I would skip: heavy conditioner on the roots of fine, flat hair. Keep it to the ends and let the volume shampoo do its job.

Try this: treat the fourth grid as a weekly layer and a daily layer, and never both at full strength. Mask on wash day, a light leave-in on the other days. Hair reads too much product as limp, not as care.

 

Acidic Bonding Concentrate 5 Minute Liquid Mask is the quick weekly one, and the Leave-In Treatment for Hair Repair is the daily one that follows it. The 24/7 Night and Day Hair Repair Serum goes on last, in small amounts. Acidic Color Gloss Gloss-in-Mask is for colored hair that has started to look dull, and All Soft Heavy Cream Hair Mask is the richer choice for dry, brittle strands. Frizz Dismiss Hair Mask finishes the frizz system.

 

One United Multi-Benefit Leave-In Conditioner Spray is the everyday detangler, the one that lives by the door for the morning rush. Extreme Anti-Snap Anti-Breakage Leave-In Conditioner is for hair that breaks when you brush it, and it earns its space in a gym bag or a drawer at the office.

 

For length and curls, the Extreme Length Leave-In Conditioner and the Acidic Bonding Curls Silicone-Free Leave-In Treatment are the daily ones, while the All Soft All-In Mask and the Extreme Length Triple Action Treatment Mask give dry or snapping hair a second weekly option. The sets at the end of the grid bundle a shampoo, a conditioner and a treatment from one line, which is the easiest way to commit to a system.

 

A pairing I like: the mask on the days you wash, the spray on the days you do not. Two products, two moods, no shelf full of half-used bottles.

 

What I would skip: a heavy cream mask on fine hair that is already limp by evening. Reach for the lighter leave-in instead.

I think the best thing you can do with a big salon line is pick one system and stay with it. Redken draws the lines itself: Acidic Bonding Concentrate runs on citric acid, Extreme is the protein-forward one, and All Soft is the moisture option for dry hair. Those are three different jobs, and mixing pieces from all three is how a routine turns muddy.

 

The brand says its bonding system is sulfate-free and paraben-free, and cites its own testing on breakage, so treat that as its claim and judge it on your own hair. Use one full bottle before deciding. Sørensen needed years to get a number right. Your hair can have a month. If you want to keep browsing, I also put together Redken Acidic Bonding and Biolage Shampoo, Masks And Leave-Ins.