Skip to main content
Rusk

Deepshine PlatinumX Purple Shampoo

Shampoo / Clarifying, deep-cleaning

  • Shampoo
  • Silicone-free
  • Lightweight
  • Not vegan · ingredient list
Size12 fl ozmost listed · 2 sizes
Price$16.80seen at one store · 12 oz · from $1.02/oz in the 33 oz
Price / oz$1.21/ozat 12 oz
Where to buy1 store · 2 sizes

Scent:

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

Manufacturer page: ruskhair.com

Personal fit

Is this right for you?

Complete the consultation to see exactly how well this product fits your hair and your goals. With 2,400+ products in our library we can match exactly the right products to you.

  • In 10 minutes we can identify your exact hair condition and traits.
  • Every product matched against your hair across the 22 factors we check.
  • A personalized routine for your daily life — your schedule, styling habits, and local weather.
  • Find products that do the same job at a lower cost.
  • Your goals, scalp, damage history, water, budget, and scent preferences all shape your plan.

$49.00 one-time consultation, no subscription

Add the optional $49/year membership for unlimited adjustments for changes in weather and lifestyle.

Start your consultation

Priced with its peers

$1.21/oz at 12 oz — less than 58% of the 805 shampoos , which mostly run $0.81–3.01/oz. The cost less.

Price and stores

Great for

Fast-oiling scalpsthat need a real reset wash
Hard waterand swimmers dealing with mineral deposit
Fine hairthat flattens under most products
Silicone-free routinesno silicones appear in the list
Cuticle-smoothing pHa pH adjuster brings it to the acidic range hair prefers

Maybe skip if

this product carries a scent
Sulfate-free routinesit uses a sulfate detergent
Very dry or damaged hairit contains fast-drying alcohol
Dry or damaged haira strong detergent system strips as it cleans
Vegan and cruelty-freeour record does not support both claims here
Tight budgetsit sits in the upper price tiers

Whether this much cleansing is right for you depends on how fast your scalp oils, how much product you layer, and your water — 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.

Cleansing strength Strong

Removes oil, buildup, and most residue — a reset wash.

Expected lather High

Thick foam that spreads quickly through the hair.

Slip and detangling Moderate

Conditioning agents are present, lower in the list.

Water-binding (humectants) Moderate

Humectants in the working part of the formula.

Scalp active None

No over-the-counter scalp active.

Hard-water defence Chelators present

Chelators are present — they bind hard-water and pool minerals.

Needs detergent to remove No

Nothing here needs a detergent wash to remove.

Protein Minor

Protein appears, low enough to be a supporting ingredient.

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
WaterWATER/AQUA/EAU solvent The base everything else is dissolved in Neutral
Ammonium Laureth Sulfate sulfate cleanser Cleanses
Ammonium Lauryl Sulfate sulfate cleanser Cleanses
PEG-150 Distearate thickener Sets the texture Stabilizes
PEG-120 Methyl Glucose Dioleate thickener Sets the texture Stabilizes
Sodium Chloride salt Thickens the formula Stabilizes
Glycol Distearate opacifier Makes the product look creamy Softens
FragranceFRAGRANCE/PARFUM fragrance The scent Fragrance
Isopropyl Alcohol drying alcohol A small amount, for fast drying Drying
Hydrolyzed Wheat Protein film former A supporting film former Protein
Limonene fragrance The scent Fragrance
Butylphenyl Methylpropional fragrance The scent Fragrance
What the list leaves out, and what it carriesThe list carries no silicones. Fragrance is on the label. Hard-water chelators are present. Contains fast-drying alcohol.
Full ingredient list (35)

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 Water · WATER/AQUA/EAU
    General function

    The base of almost every rinse-off and cream hair product. It carries everything else and is normally the first ingredient on the label.

    Leading ingredient

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

    • solvent
  • 2 Ammonium Laureth Sulfate
    General function

    A sulfate detergent that foams quickly and cleans thoroughly.

    Leading ingredient

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

    May suitBuild-up-sensitive routines

    A sulfate detergent removes deposited silicone, wax and styling films in one wash, which is what resets a routine before build-up is visible.

    May suitFine or easily flattened hair

    Fine hair that goes limp under conditioning films usually reads a full detergent wash as volume returning.

    May not suitDry, coarse, or high-porosity hair

    Coarse and high-porosity hair loses water quickly on its own; an efficient detergent removes the surface oils that were slowing that down.

    PubChem
    • sulfate cleanser
    • cleanser
  • 3 Ammonium Lauryl Sulfate
    General function

    A sulfate detergent similar in strength to sodium lauryl sulfate, used for fast, high foam.

    Leading ingredient

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

    May suitBuild-up-sensitive routines

    A sulfate detergent removes deposited silicone, wax and styling films in one wash, which is what resets a routine before build-up is visible.

    May suitFine or easily flattened hair

    Fine hair that goes limp under conditioning films usually reads a full detergent wash as volume returning.

    May not suitDry, coarse, or high-porosity hair

    Coarse and high-porosity hair loses water quickly on its own; an efficient detergent removes the surface oils that were slowing that down.

    PubChem
    • sulfate cleanser
    • cleanser
  • 4 PEG-150 Distearate
    General function

    A thickener that gives shampoo and body wash their pourable, slightly gel-like texture.

    Supporting ingredient

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

    • thickener
    • emulsifier
  • 5 PEG-120 Methyl Glucose Dioleate
    General function

    A sugar-derived thickener used to build body in sulfate-free cleansers.

    Supporting ingredient

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

    • thickener
    • emulsifier
  • 6 Sodium Chloride
    General function

    Table salt. In shampoo it is used to thicken the liquid, not to treat the hair.

    Supporting ingredient

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

    PubChem
    • salt
    • thickener
  • 7 Glycol Distearate
    General function

    A wax that gives shampoo its pearly look and a slightly richer feel.

    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

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

    PubChem
    • opacifier
    • emollient
  • Below about this point, order stops being meaningful — these are typically used at 1% or less.
  • 8 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
  • 9 Polyquaternium-10
    General function

    A cellulose-based conditioning polymer that leaves a thin, static-reducing film. Very common in shampoos as the ingredient that keeps them from stripping.

    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 suitCurls or waves needing flexible hold

    Cationic polymers hold a curl loosely and stay soft, which is why they turn up in definition products rather than firm-hold ones.

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

    A cationic polymer stays on the hair through rinsing, which is what keeps static and combing friction down after the wash.

    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.

    • conditioning agent
    • film former
    • polymer
  • 10 Propylene Glycol
    General function

    A small humectant and solvent that keeps formulas stable and helps active ingredients spread.

    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 suitFine or easily flattened hair

    Light and water-binding rather than oily, so it hydrates without contributing weight.

    May suitVery dry or highly damaged hair

    A small water-binding solvent. It holds moisture and helps the rest of the formula spread evenly over the strand.

    DependsClimate-sensitive or frizz-prone hair

    A humectant follows the air: it holds water in humid conditions and can give it up in very dry ones. Climate decides what it does more than the label does.

    PubChem
    • humectant
    • solvent
  • 11 Tetrasodium EDTA
    General function

    Binds the metal ions in hard water so they cannot dull hair or destabilise the formula.

    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 suitBuild-up-sensitive routines

    Binds the calcium and magnesium in hard water, which is what stops mineral deposits accumulating on the strand wash after wash.

    May suitGray, silver, or brass-prone hair

    Copper and iron carried in tap water deposit on the strand and read as a dull, warm cast on gray or light hair. A chelator holds those metals in solution so the wash carries them off.

    PubChem
    • hard-water chelator
  • 12 Citric Acid
    General function

    Used to bring the product to a slightly acidic pH, which helps the cuticle lie flat. It is almost always near the end of the list.

    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 suitBuild-up-sensitive routines

    Holds hard-water minerals in solution so they rinse away instead of depositing on the hair.

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

    The acid side of pH adjustment, and the reason it matters is measured: alkaline formulas raise the fibre's surface negative charge, increase friction between strands and lift the scales, while lower-pH ones do the reverse.

    May suitGray, silver, or brass-prone hair

    Where a warm cast comes from water minerals rather than from the hair itself, holding those metals in solution is what removes it.

    International Journal of Trichology
    • pH adjuster
    • hard-water chelator
  • 13 Sodium Bicarbonate
    General function

    Baking soda. Used in trace amounts to raise pH; at higher levels it is alkaline enough to swell the cuticle.

    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 suitFine or easily flattened hair

    Takes up oil at the root, which is where fine hair goes flat first.

    DependsFrizz-prone, damaged, or high-friction hair

    pH adjusters are how a formula is brought to a chosen acidity, and an acidic formula keeps the cuticle lying flatter than an alkaline one. Which way this one moves the pH depends on the formula, and the finished pH is not on the label.

    • pH adjuster
    • absorbent
  • 14 Ext. Violet 2 (CI 60730)
    General function

    A certified colour that tints the product itself. It does not colour hair.

    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 suitGray, silver, or brass-prone hair

    A violet or blue colorant sits opposite yellow on the colour wheel, so a trace of it deposited on the surface makes a warm cast read cooler. It washes out over the following few washes.

    • colourant
    • direct dye
    • violet dye
  • 15 Methyl Gluceth-10
    General function

    A sugar-derived humectant that also helps a formula stay blended.

    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 suitDry, coarse, or high-porosity hair

    High-porosity hair loses water fast; a humectant holds some of it in place for longer than the wash itself would.

    May suitVery dry or highly damaged hair

    Binds water into the outer layers of the strand, and water is what makes dry hair flexible again rather than brittle.

    DependsClimate-sensitive or frizz-prone hair

    A humectant moves water in whichever direction the air allows: it holds moisture in humid conditions and can pull it back out of hair in very dry ones.

    • humectant
    • emulsifier
  • 16 Glycerin
    General function

    A small water-loving molecule that draws moisture into the hair and holds it there. It is the most common softening ingredient in conditioners and leave-ins.

    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 suitDry, coarse, or high-porosity hair

    High-porosity hair loses water fast; a humectant holds some of it in place for longer than the wash itself would.

    May suitVery dry or highly damaged hair

    Binds water into the outer layers of the strand, and water is what makes dry hair flexible again rather than brittle.

    DependsClimate-sensitive or frizz-prone hair

    Water moves both ways. Measured across concentrations, glycerin solutions give water up in some conditions and take it from the air in others. What it does for you depends on how much of it is there and on the air around it.

    Scientific Reports
    • humectant
  • 17 Magnesium Nitrate
    • salt
  • 18 Honey · HONEY (MEL)
    General function

    A natural sugar-based humectant that holds water against the strand.

    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 suitFine or easily flattened hair

    Hydration with no oil attached, so it adds very little weight even high on a list.

    May suitVery dry or highly damaged hair

    Aloe is mostly water carrying sugars that bind more of it, which is why it turns up as the base of moisture-first formulas.

    DependsClimate-sensitive or frizz-prone hair

    A humectant follows the air: it holds water in humid conditions and can give it up in very dry ones. Climate decides what it does more than the label does.

    • humectant
    • botanical extract
  • 19 Isopropyl Alcohol
    General function

    A fast-evaporating alcohol used as a solvent and to speed drying. Well down the list it is a processing aid; near the top it can leave hair feeling dry.

    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 suitFine or easily flattened hair

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

    PubChem
    • drying alcohol
    • solvent
  • 20 Lavandula Angustifolia (Lavender) Extract
    • botanical extract
  • 21 Citrus Grandis (Grapefruit) Fruit Extract
    • botanical extract
  • 22 Citrus Aurantifolia (Lime) Fruit Extract
    • botanical extract
  • 23 Citrus Limon (Lemon) Fruit Extract
    • botanical extract
  • 24 Citrus Aurantium Dulcis (Orange) Fruit Extract
    • botanical extract
  • 25 Hydrolyzed Wheat Protein
    General function

    Wheat protein broken into fragments small enough to cling to the hair. It adds temporary strength and body; too much can feel stiff.

    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 suitFrizz-prone, damaged, or high-friction hair

    Filling surface gaps evens out the cuticle, which is part of what makes damaged hair comb and reflect light more like undamaged hair.

    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.

    • film former
    • protein
    • hydrolysed protein
  • 26 Methylchloroisothiazolinone
    • isothiazolinone
    • preservative
  • 27 Methylisothiazolinone
    • isothiazolinone
    • preservative
  • 28 Phenoxyethanol
    • preservative
  • 29 Magnesium Chloride
    • salt
  • 30 Benzyl Alcohol
    • preservative
    • solvent
  • 31 Potassium Sorbate
    • preservative
  • 32 Sodium Benzoate
    • preservative
  • 33 Limonene
    General function

    A citrus-smelling fragrance component that EU rules require to be named separately 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.

    PubChem
    • fragrance
    • named fragrance allergen
  • 34 Butylphenyl Methylpropional
    General function

    A floral fragrance component (lilial) named separately as a recognised allergen; increasingly reformulated out.

    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
  • 35 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

  • 6 botanical extracts
  • 6 preservatives
  • 4 solvents
  • 4 fragrances
  • 4 humectants
  • 3 thickeners
  • 3 emulsifiers
  • 3 salts
  • 3 named fragrance allergens
  • 2 sulfate cleansers
  • 2 cleansers
  • 2 film formers
  • 2 hard-water chelators
  • 2 pH adjusters

Ingredient list captured 2026-08-24. Formulas change — check the package in your hand when an ingredient matters to you.

Price · 12 oz

Seen at $16.80 1 store · checked Aug 22
Good value under $13 Under $1.11/oz it costs less than three-quarters of the 7 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 $19 at this size.

Sizes

12 ozmost listed
$16.80
$1.40/oz
33 oz
$33.60
$1.02/oz

The 33 oz costs 27% less per ounce than the 12 oz.

Show the price ladder
Where we’ve seen it2 listings · 1 store

12 ozmost listed

33 ozBest per ounce

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. 12 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. Seen at $16.80 is the price we have observed for the 12 oz. We need three stores before we call a price commonly seen.
  3. Good value under $13 comes from the 7 products we score as doing the same job as this one. A quarter of them cost less than $1.11/oz; at 12 oz that is $13. Under that line you are paying less than most of them.
  4. Each size is guarded on its own, so a multipack or a marketplace listing at one size cannot move another.
  5. About $19 is what those same products typically cost at this size — the midpoint of their prices per ounce, scaled to 12 oz.

Formula

Formula score
9 of 10

A complete read of the format at an ordinary price: mid-range per ounce among shampoos, with the working systems present.

How the score is counted
  • 2 products that do the same job cost less per ounce
  • Costs less per ounce than 58% of the 805 shampoos we’ve priced
  • Covers 6 of the 7 things a shampoo should do
  • Reviewers mention 2 things they like about how it performs
  • A working detergent systemWhat actually removes oil and product.3 pts
  • Slip for detanglingReduces the force it takes to comb wet hair.2 pts
  • A humectantBinds water into the hair.1 pt
  • A hard-water chelatorBinds the minerals that dull hair in hard water.1 pt
  • A pH adjusterBrings the formula to the acidic pH hair prefers.1 pt
  • No detergent-dependent filmNothing that needs a clarifying wash to remove.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.

ClairolClosest function Clairol Shimmer Lights Purple Shampoo $0.62/oz $0.59/oz less
  • Deep clean
  • Hard water
  • Silicone-free
Function
  • Water-binding (humectants)
  • Film formers
Also
  • Fresh scent
  • Drugstore tier
  • 32 oz bottle
Compare
FanolaLowest cost per oz Fanola No Yellow Shampoo
  • Deep clean
  • Lightweight
  • Silicone-free
· Close function
Function
  • Slip and detangling
  • Hard-water defence
  • Film formers
Also
  • Floral scent
  • Drugstore tier
  • 11.7 oz bottle
Compare

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?

Only for a specific need
Best user

Scalps that oil up within a day who want a proper reset wash and a hard-water chelator

Biggest tradeoff

Worth skipping for anyone sensitive to fragrance, sulfate-free routines and fresh keratin treatments, or very dry or high-damage hair

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.

0
SupportedBacked by ingredients
0
Partly supportedSome supporting logic
1
Stated by brandNo clear evidence
0
Potential conflictFormula works against claim
RUSK Deepshine PlatinumX Shampoo is a gentle cleansing shampoo formulated to neutralize yellow, boost brightness, and eliminate brassiness.

Nothing in the list reads as a shine system.

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.

Scent is frequently praised as a standout feature

general reviewers

Reliably tones out yellow/brassy tones on blonde and highlighted hair, several users calling out reduced brassiness after a few uses

reviewers with blonde or highlighted hair

Some reviewers report the formula is thin/runny and does not lather up well

general reviewers

A minority of reviewers found it left hair feeling dry despite the brightening effect

reviewers with color-treated hair

More from Rusk

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.
  • 8 sources consulted for this product (6 manufacturer or regulatory, 2 retailer, 0 editorial), last checked 2026-08-25.
  • Ingredient references are linked for 11 of 18 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 2026-08-25.