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BioSilk

Silk Therapy Original

Finisher / Serum, glossing

  • Finisher
  • serum
  • Sulfate-free
  • Moisture-rich
Size2.26 fl oz
Price$13–15commonly seen · 2.26 oz
Price / oz$6.32/ozat 2.26 oz

Scent:

The ingredient list declares fragrance. What it smells of is not stated, and we do not guess.

Listing used for research: ulta.com

Personal fit

Is this right for you?

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Priced with its peers

$6.32/oz at 2.26 oz — less than 62% of the 79 serums , which mostly run $3.27–14.46/oz. The cost less.

Price and stores

Great for

Protein-hungry hairthat stretches and stays stretched when wet
Maximum slipfor hair that tangles the moment it is wet
Dry, thirsty hairhumectants and emollients both sit up front
Dull-looking haira recognised shine system is present
Aerosol avoidancea pump or tube, not a pressurised can
A wide range of haira middle-of-the-range weight

Maybe skip if

this product carries a scent
Curly-method routinesthese silicones need a detergent to remove
Protein-sensitive hairthat goes stiff or straw-like on protein
Very dry or damaged hairit contains fast-drying alcohol

Whether a finisher this rich will read as shine or as grease depends on your strand thickness and oil rate — that is what the consultation works out.

What the formula actually does

Read from the label, not the marketing

Each row says where it comes from: F means we derived it from this product’s own ingredient list, S means it is a claim the brand makes that the formula neither confirms nor contradicts.

Shine system Silicone serum

A silicone or oil blend does the shine work here.

Weight on the hair Medium

Middle of the range — noticeable on fine hair, light on coarse hair.

Oils and butters None

No oils or butters in the list.

Needs detergent to remove Yes

Water-insoluble silicones or waxes: a detergent wash is what removes them.

Fast-drying alcohol Present

Fast-drying alcohol is present — it speeds drying and can read dry on the hair.

Fragrance Prominent

Fragrance sits in the first eight ingredients — a larger share of the formula.

from the formula stated by the brand reported by reviewers Scale: 1 dot low · 5 dots high, within this product type.

Ingredients that matter

The ingredients that change a decision

The workhorse ingredients plus anything lower down that changes a decision. These chips name what an ingredient does — they are not safety scores, and no ingredient here is rated good or bad on its own.

IngredientWhat it doesWhy it mattersChip
C13-14 Isoalkane emollient Softens and smooths the strand Shine
Dimethiconol silicone The shine system Buildup
Isododecane solvent The base everything else is dissolved in Shine
Alcohol Denat. drying alcohol Speeds drying — and can read dry on the hair Drying
Panthenol humectant Pulls water into the hair Detangles
Ethyl Ester Of Hydrolyzed Silk conditioning agent Conditions and softens — this is what makes it comb through Protein
FragranceFragrance (Parfum) fragrance The scent Fragrance
Alpha-Isomethyl Ionone fragrance The scent Fragrance
Benzyl Benzoate fragrance The scent Fragrance
Citronellol fragrance The scent Fragrance
Eugenol fragrance The scent Fragrance
Geraniol fragrance The scent Fragrance
What the list leaves out, and what it carriesNo sulfates. Protein-forward — a strengthening formula, not a moisture one. Contains fragrance. The silicones here need a detergent wash to come off.
Full ingredient list (15)

US labelling rules put ingredients above 1% in descending order of amount; below 1% they may be listed in any order. Annotations keep three readings separate: the ingredient's general function, its role in this product type, and what its position can support.

  • 1 C13-14 Isoalkane
    General function

    A light carrier that spreads other ingredients and leaves a dry finish.

    Leading ingredient

    Listed in the first three ingredients, it is likely a structural part of this formula.

    May suitFrizz-prone, damaged, or high-friction hair

    Emollients fill and smooth the surface of the strand, which lowers the friction that lifts the cuticle and reads as roughness.

    • emollient
    • solvent
  • 2 Dimethiconol
    General function

    A high-shine silicone often paired with dimethicone for a smoother, glossier finish.

    Leading ingredient

    Listed in the first three ingredients, it is likely a structural part of this formula.

    May suitClimate-sensitive or frizz-prone hair

    A surface film slows how quickly humidity reaches the cortex, which is what limits swelling-driven frizz in damp air.

    May suitFrizz-prone, damaged, or high-friction hair

    Lays a smooth film along the cuticle, which lowers combing friction and flattens the surface irregularities that read as frizz.

    May not suitBuild-up-sensitive routines

    Dimethicone does not disperse in water. On a routine that skips detergent it stays on the hair and accumulates wash after wash.

    PubChem
    • silicone
    • emollient
  • 3 Isododecane
    General function

    A fast-evaporating carrier that lets oils and polymers spread thinly, then leaves nothing behind.

    Leading ingredient

    Listed in the first three ingredients, it is likely a structural part of this formula.

    May suitFrizz-prone, damaged, or high-friction hair

    Emollients fill and smooth the surface of the strand, which lowers the friction that lifts the cuticle and reads as roughness.

    PubChem
    • solvent
    • emollient
  • 4 Alcohol Denat.
    General function

    Fast-drying alcohol used to make sprays set quickly. In leave-on products it can leave hair feeling dry, especially in high position on the list.

    Supporting ingredient

    Listed in positions 4–8, it likely makes a meaningful contribution alongside the formula's main ingredients.

    May suitFine or easily flattened hair

    Evaporates on contact, which is how a spray sets almost instantly and leaves no weight behind it.

    May not suitDry, coarse, or high-porosity hair

    Porous hair gives water up easily as it is; a fast-evaporating solvent high on the list accelerates that.

    May not suitVery dry or highly damaged hair

    It evaporates quickly and takes some water with it. On hair already short of moisture, a formula built on a lot of it can finish drier than it started.

    PubChem
    • drying alcohol
    • solvent
  • 5 Panthenol
    General function

    Provitamin B5. It draws in water and penetrates the strand a little, which is why it is the standard ingredient for softness and shine claims.

    Supporting ingredient

    Listed in positions 4–8, it likely makes a meaningful contribution alongside the formula's main ingredients.

    May suitFine or easily flattened hair

    It hydrates without adding oil or a film, which is the combination fine hair usually needs.

    May suitFrizz-prone, damaged, or high-friction hair

    Deposits a lubricating layer that makes combing easier, which is most of what stops mechanical damage adding to frizz.

    May suitVery dry or highly damaged hair

    A humectant that also penetrates the cuticle, so it holds water inside the strand rather than only on the surface.

    PubChem
    • humectant
    • conditioning agent
    • vitamin
  • 6 Ethyl Ester Of Hydrolyzed Silk
    General function

    A protein given a positive charge so it deposits where hair is damaged. It conditions and adds temporary firmness in one ingredient.

    Supporting ingredient

    Listed in positions 4–8, it likely makes a meaningful contribution alongside the formula's main ingredients.

    May suitFrizz-prone, damaged, or high-friction hair

    A cationic conditioning agent: it binds to the damaged, negatively charged parts of the cuticle and lowers combing friction there.

    May suitMaximum-hold styling

    Film formers are what hold a style: they dry into a connected film across the strands so the shape resists movement.

    May suitVery dry or highly damaged hair

    Hydrolysed fragments are small enough to sit in the gaps of a worn cuticle for a wash or two, temporarily restoring stiffness and cutting breakage in combing.

    • conditioning agent
    • film former
    • protein
    • hydrolysed protein
  • Below about this point, order stops being meaningful — these are typically used at 1% or less.
  • 7 Fragrance · Fragrance (Parfum)
    General function

    An undisclosed blend of scent ingredients. Regulations let it stay unlisted, so a fragrance-free product is the only way to be certain what is not in it.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May not suitFragrance-sensitive routines

    Declared fragrance. On a fragrance-sensitive routine this is the line that decides it, wherever it sits on the label.

    • fragrance
    • declared fragrance
  • 8 Alpha-Isomethyl Ionone
    General function

    A violet-like fragrance component named separately as a recognised allergen.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May not suitFragrance-sensitive routines

    One of the 26 scent components the EU requires to be named individually above a threshold. It is named because it is a known contact allergen, not because it is unusual.

    PubChem
    • fragrance
    • named fragrance allergen
  • 9 Benzyl Benzoate
    General function

    A fragrance component with a faint balsamic scent, named separately on the label because it is a recognised contact allergen.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May not suitFragrance-sensitive routines

    One of the 26 scent components the EU requires to be named individually above a threshold. It is named because it is a known contact allergen, not because it is unusual.

    PubChem
    • fragrance
    • named fragrance allergen
  • 10 Citronellol
    General function

    A rose-like fragrance component named separately as a recognised allergen.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May not suitFragrance-sensitive routines

    One of the 26 scent components the EU requires to be named individually above a threshold. It is named because it is a known contact allergen, not because it is unusual.

    PubChem
    • fragrance
    • named fragrance allergen
  • 11 Eugenol
    General function

    A clove-scented fragrance component listed separately as a recognised allergen.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May not suitFragrance-sensitive routines

    One of the 26 scent components the EU requires to be named individually above a threshold. It is named because it is a known contact allergen, not because it is unusual.

    PubChem
    • fragrance
    • named fragrance allergen
  • 12 Geraniol
    General function

    A rose-scented fragrance component, listed on its own because some people react to it.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May not suitFragrance-sensitive routines

    One of the 26 scent components the EU requires to be named individually above a threshold. It is named because it is a known contact allergen, not because it is unusual.

    • fragrance
    • named fragrance allergen
  • 13 Hexyl Cinnamal
    General function

    A jasmine-like fragrance component named separately as a recognised allergen.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May not suitFragrance-sensitive routines

    One of the 26 scent components the EU requires to be named individually above a threshold. It is named because it is a known contact allergen, not because it is unusual.

    PubChem
    • fragrance
    • named fragrance allergen
  • 14 Hydroxycitronellal
    General function

    A soft floral fragrance component named separately as a recognised allergen.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May not suitFragrance-sensitive routines

    One of the 26 scent components the EU requires to be named individually above a threshold. It is named because it is a known contact allergen, not because it is unusual.

    PubChem
    • fragrance
    • named fragrance allergen
  • 15 Linalool
    General function

    A floral fragrance component listed separately as a recognised contact allergen.

    Estimated lower-concentration zone

    It appears around or below the estimated 1% line, where label order no longer indicates relative amount; its role may be minor or technical.

    May not suitFragrance-sensitive routines

    One of the 26 scent components the EU requires to be named individually above a threshold. It is named because it is a known contact allergen, not because it is unusual.

    PubChem
    • fragrance
    • named fragrance allergen

What the whole list adds up to

  • 9 fragrances
  • 8 named fragrance allergens
  • 3 emollients
  • 3 solvents
  • 1 silicone
  • 1 drying alcohol
  • 1 humectant
  • 1 conditioning agent
  • 1 vitamin
  • 1 conditioning agent
  • 1 film former
  • 1 protein
  • 1 hydrolysed protein
  • 1 declared fragrance

Ingredient list captured 2026-08-27. Formulas change — check the package in your hand when an ingredient matters to you.

Price · 2.26 oz

Commonly seen $13–15 Midpoint $14.29 · 3 stores · checked Aug 29
Good value under $13 Under $5.64/oz it costs less than three-quarters of the 8 products we score as doing the same job

Priced above the products that do the same job. Stores sell it above the $13 line; products that do this job typically go for about $18 at this size.

Show the price ladder
Where we’ve seen it4 listings · 4 stores

Sorted by price per ounce. Dated observations from our research, not live prices. Direct store pages, no affiliate links. We don’t sell this product.

How we work this out
  1. 2.26 oz is the size stores list most often; every comparison on this page is made at it. Other sizes are shown in the Sizes row and the store list.
  2. Commonly seen is the middle half of current prices for the 2.26 oz at recognised stores — the cheapest quarter and the dearest quarter are left out, so one sale or one overpriced listing can’t move it.
  3. Good value under $13 comes from the 8 products we score as doing the same job as this one. A quarter of them cost less than $5.64/oz; at 2.26 oz that is $13. Under that line you are paying less than most of them.
  4. About $18 is what those same products typically cost at this size — the midpoint of their prices per ounce, scaled to 2.26 oz.

Formula

Formula score
9 of 10

The formula carries the systems a serum is built around, and it sits in the middle of the range for serums per ounce.

How the score is counted
  • 2 products we score as doing the same job cost less per ounce
  • Costs less per ounce than 62% of the 79 serums we’ve priced
  • Covers 5 of the 6 things a serum should do
  • Reviewers mention 3 things they like about how it performs
  • A shine systemThe silicone, oil, or ester that produces gloss.3 pts
  • A weightless carrierDelivers the shine without leaving grease.2 pts
  • Oils or butters in the working zoneSoftens the strand rather than just coating it.2 pts
  • An antioxidantKeeps the oils in the bottle from going off.1 pt
  • No drying alcohol in the first threeFast drying without leading on alcohol.1 pt
  • Fragrance kept out of the top eightScent as a finishing touch, not a major share.1 pt

The formula score is completeness for the job: the share of the systems this product type is normally built around that we can find in this list, weighted. It is not efficacy, not quality, and it never compares across product types.

Does the same job, for less

Same derived functions — what it cleans, conditions, coats or holds — at a lower cost per ounce. Scent, texture and where you buy it can still differ.

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  • Shine
Function
  • Fast-drying alcohol
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  • 6.5 oz bottle
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One 'n OnlyLowest cost per oz Shiny Silver Ultra Shine Spray $2.50/oz $3.82/oz less
  • Shine
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· Close function
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See more alternatives in the product library

These are functional neighbours, not personal recommendations — they are close on formula, not chosen for anyone. Get the one that fits your hair, routine, and budget

Suits every hair pattern

Final decision

Should you buy it?

A solid pick for the hair it suits
Best user

Soft, over-stretchy hair who want protein high in the formula and real detangling slip

Biggest tradeoff

Worth skipping for anyone sensitive to fragrance, curly-method routines, or hair that stiffens on protein

We do not sell products or take placement fees. This page states what the formula and the prices show; the consultation is what matches it to a person.

Claims check

What the brand says, against what the formula shows

Claims are quoted from the brand. We only mark one supported, partly supported, or conflicting when the ingredient list actually speaks to it; everything else stays "stated by the brand", which is not a criticism — most claims simply cannot be read off a label.

3
SupportedBacked by ingredients
0
Partly supportedSome supporting logic
2
Stated by brandNo clear evidence
0
Potential conflictFormula works against claim
smooths and protects

Silicones or film formers smooth the cuticle, which is the usual mechanism.

  • Dimethiconol
  • Ethyl Ester Of Hydrolyzed Silk
Supported

Smoother strands, less frizz.

all hair types

No formula reads the same on every texture; our fit panel is the better guide.

Stated by brand

See the fit panel instead.

helps prevent split ends

Protein sits in the first eight ingredients.

  • Ethyl Ester Of Hydrolyzed Silk
Supported

Reinforces a damaged strand.

adds shine

The formula carries a recognised shine system — silicone, oil, or light ester.

  • Dimethiconol
Supported

Reflects light for visible shine.

leave-in replenishing treatment

This is a marketing claim; an ingredient list cannot speak to it.

Stated by brand

Can’t be confirmed from label.

How to read this

We look at the first 10–15 ingredients and what they do in a formula — not marketing. If the list doesn't speak to a claim, we don't assume.

Reviewers

What people report

Recurring themes our researchers wrote in their own words from sourced reviews. We do not store or scrape star ratings.

A very curly-haired customer uses it daily and says it controls frizz very well.

A customer who applies a few drops after drying says the formula lasts a long time and receives compliments on its scent.

A long-time user says a nickel-sized amount on damp or dry hair makes dry hair soft and shiny, while a little goes a long way.

A reviewer says it works well for thick curly hair after drying but leaves their straight thin hair looking oily and limp.

How this page was made

  • Everything above is generated from our researched product record — identity, the ingredient list as printed, the brand's own claims, dated price observations, and review themes written in our researchers' own words. No part of this page is written per product.
  • The value band is a fixed label over two stored numbers: this product’s cost per ounce as a percentile of every product of this type we have priced, each at the size it is most often sold in, and how many products we score as doing the same job cost at least a quarter less per ounce.
  • Both scores out of ten are defined on this page. The formula score is completeness for the job, computed from a fixed per-format checklist shown beneath the gauge; the price score is cost per ounce against every product of this type we have priced.
  • The "Is this right for you?" panel reads only your own consultation answers, and it applies exactly the filters our recommendation engine applies. It is computed when you load the page and is never stored on it.
  • 2 sources consulted for this product (1 manufacturer or regulatory, 1 retailer, 0 editorial), last checked 2026-08-27.
  • Ingredient references are linked for 11 of 15 product-aware annotations on this page. Fit notes are conditional formulation guidance, not a conclusion about the finished product or about you.
  • We have not tested this product in a lab and we do not physically test your hair. Formula readings come from the ingredient list; behaviour claims are labelled as the brand's.
  • Ingredient order tells you relative amount only above roughly 1%. Prices are observations on the dates shown and change without notice.
  • Ingredient names link to our ingredient library, where each entry shows what it does, which product types use it, and where it usually sits on a label across everything we have researched.
  • This is cosmetic information, not medical advice, and nothing here diagnoses or treats a health condition.
  • Formula readings: derivation v22. Record last updated 2026-08-27.