SDA 40-B: A Formulator's Guide for Fragrance & Cosmetics
SDA 40-B: a practical guide for fragrance and cosmetic formulators.
The product page tells you what 40-B is. This tells you how to formulate with it: why it beats 3-C on skin, how it reads on your INCI list, the dilution math for fragrance, and where the OTC monograph draws its lines.
Choosing 40-B is the easy part. Formulating well with it is where the work is. If you've read the product page, you know the chemistry and the applications. This guide assumes that and goes past it: into the decisions you actually make at the bench.
One assumption up front: this is written for formulators producing products for sale, which means operating under a TTB Industrial Alcohol User Permit. If that part is still fuzzy, the formula-system guide lays out why commercial use of SDA requires the permit regardless of how little you buy at a time. With that settled, let's formulate.
Why 40-B beats 3-C on skin.
The grade comparison says 40-B is the cosmetic choice and 3-C is the solvent choice. True, but that's the conclusion, not the reason. The reason lives in the denaturant, and it matters because the denaturant is the only thing that distinguishes these two — the ethanol underneath is identical.
40-B is denatured with tert-butyl alcohol plus a whisper of denatonium benzoate. 3-C is denatured with 5% isopropyl alcohol. That difference decides everything downstream for a skin-contact product.
Denatonium works at vanishingly low levels: bitter enough that only a trace is needed, so it contributes essentially nothing to odor, feel, or your active percentages. tert-Butyl alcohol is a minor fraction. The net effect on a finished cosmetic is close to none, which is exactly what you want.
That 5% IPA is a real fraction of the volume, with its own faint odor and its own evaporation behavior. In a degreaser or an extraction solvent, irrelevant. In a fine fragrance or a leave-on cosmetic, it's a variable you now have to account for — and can't easily remove.
So the rule of thumb — 40-B for skin and scent, 3-C for solvent work — isn't arbitrary. It's that 40-B's denaturant load is small and inert enough to disappear into a finished product, and 3-C's isn't. When what you're selling is the smell or the skin feel, you can't afford a denaturant that shows up.
The safety record backs the choice. The Cosmetic Ingredient Review panel assessed SD Alcohol 40-B and found it well-tolerated in skin-contact use — the kind of data that's reassuring when you're putting it in a leave-on product.
Denatonium as denaturant. The concentration at which it's effective — which is why it doesn't touch your formula.
Tested skin-contact range. 40-B formulas at these loads were non-irritating and non-sensitizing in human patch tests.
Barrier disruption from ethanol. Dermal ethanol doesn't measurably breach the skin barrier or build systemic levels.
Source: CIR Final Report on Alcohol Denat. and SD Alcohols (incl. 40-B). Figures are from published safety assessment, not a substitute for testing your own formulation.
How 40-B reads on your INCI list.
This trips up first-time formulators constantly, so here's the clean version. There are two names in play, and they are not interchangeable in the way people assume.
For a US product, you can generally list it either way: “SD Alcohol 40-B” or “Alcohol Denat.” The first is more transparent about what's in the bottle; the second is the harmonized name buyers see most. What you should not do is invent a third phrasing like “denatured ethanol” on the ingredient line — that's neither the INCI name nor the TTB designation.
And here's the point the product page can't make for you: the denaturants don't get their own line on your label. The denatonium and tert-butyl alcohol are part of what “SD Alcohol 40-B” or “Alcohol Denat.” already denotes. That's not a loophole: it's how the nomenclature is built. The designation is the disclosure.
Denaturant rules differ by market, and this bites exporters. The EU does not accept ethanol denatured with denatonium benzoate alone, and the US bars some denaturants the EU uses. A formula built on a US SD Alcohol grade may not be legal to sell in Europe as-is. Confirm the denaturant is accepted in every market you ship to before you commit a formula — this is a reformulation you don't want to discover after launch.
Fragrance dilution, by the numbers.
Fragrance is where 40-B earns its keep, because here the solvent's neutrality is the whole product. Perfume is, mechanically, aromatic compounds dissolved in ethanol: the ratio of oil to alcohol is what separates a parfum from a body splash. These are industry conventions, not legal limits, and every house tunes its own, but the conventional ranges are worth knowing as a starting point.
| Type | Aromatic compound | Balance | Character |
|---|---|---|---|
| Parfum / Extrait | 20–30% | Ethanol (40-B) | Richest, longest wear; smallest alcohol fraction |
| Eau de Parfum | 15–20% | Ethanol (40-B) | The modern default for “a perfume” |
| Eau de Toilette | 5–15% | Ethanol (40-B) | Lighter, brighter, shorter wear |
| Eau de Cologne | 2–5% | Ethanol (40-B) | Splash-style, citrus-forward, fleeting |
| Body / Hair mist | 1–3% | Ethanol + water | Sheer; often where 190 proof's water is welcome |
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Conventional ranges; houses vary. Percentages are of aromatic compound by weight; the balance is largely ethanol, with small amounts of water and fixatives depending on the build.
A worked example, because the abstraction hides the practical bit. Say you're building a 100 g eau de parfum at 18% fragrance load: that's 18 g of your aromatic compound and roughly 82 g of ethanol, before any water or fixative adjustments. Use 200 proof 40-B and you're controlling the water yourself; a small, deliberate water addition (often a few percent) can round off harsh edges and help the blend “sit.” This is why perfumers reach for 200 proof here — they want to add water by choice, not inherit 5% they didn't budget for.
Then comes the part beginners skip: maceration. A fresh blend smells raw. Let it rest: typically days to several weeks, cool and dark, and the alcohol and aromatics marry into something rounder. 40-B's neutrality is what makes maceration trustworthy: the solvent isn't contributing notes that drift over those weeks, so what you smell at the end is your composition, not the container.
In fragrance, the solvent's job is to disappear. That's the entire case for 40-B.
Topical OTC and the hand-sanitizer monograph.
The moment your product makes a drug claim — kills germs, treats, protects — it stops being a cosmetic and becomes an OTC drug, and a different rulebook applies. Hand sanitizer is the case every formulator runs into, so it's worth getting concrete.
Alcohol-based hand sanitizer is regulated under FDA's OTC topical-antiseptic framework. The operative number: ethanol at a 60–95% v/v final concentration in aqueous solution, and the ethanol must be denatured per TTB rules in 27 CFR Part 20 — which is precisely what an SDA grade like 40-B is. The regulation and your raw material line up by design.
Higher alcohol percentage is not automatically better. Efficacy studies have found that a well-formulated product at the lower end of the range can outperform a sloppy one at a higher percentage — formulation and contact time matter as much as raw concentration. Chasing the highest number on the label is the rookie move; building the whole formula well is the professional one.
Two timing notes that matter for compliance. First, this is governed by a tentative final monograph — long-standing and treated as operative, but worth knowing it carries that status. Second, the temporary flexibilities FDA issued during the 2020 COVID emergency — which loosened several rules — were withdrawn at the end of 2021. Production is back to standard monograph terms. If your reference material is from 2020, it's out of date; spec against the current monograph.
An OTC drug carries obligations a cosmetic doesn't — facility registration, CGMP, drug labeling, and active-ingredient rules among them. This guide explains where 40-B fits the monograph; it is not a complete compliance roadmap for launching an OTC drug. Confirm the full requirements with FDA and a regulatory professional before you sell.
What separates a spec from a formula.
The product page gives you the spec. Formulating well with 40-B is a handful of judgments past it: knowing the denaturant is inert enough to disappear, so you can trust it in leave-on and fine-fragrance work; listing it correctly on your INCI line and checking the denaturant against every market you ship to; building your dilution to the product you actually want and using 200 proof to control the water yourself; and recognizing the moment a drug claim pulls you into the OTC rulebook, where the monograph and your permit both apply.
None of that is on the label. All of it is the difference between buying the right ethanol and building the right product.
How does SDA 40-B appear on a cosmetic ingredient label?
Two accepted names. “Alcohol Denat.” is the official INCI name, recognized globally. “SD Alcohol 40-B” is the US TTB designation, also accepted on US labels and more specific about which denaturants are present. For a US product you can list it either way. The denaturants themselves don't get a separate line, the designation already denotes them.
Is SDA 40-B safe for skin?
The Cosmetic Ingredient Review panel assessed SD Alcohol 40-B as well-tolerated in skin-contact use: formulas at 12% and 29% were non-irritating and non-sensitizing in human patch tests, and dermal ethanol doesn't measurably breach the skin barrier. As always, test your own finished formulation, but the safety record is why 40-B is the leave-on and fragrance standard.
How long should I macerate a fragrance?
The floor is 48 to 72 hours. Light citrus and floral blends often settle in 1 to 2 weeks; the commercial standard is 2 to 4 weeks, where top, heart, and base notes harmonize. Heavy compositions with woods, resins, or oud can need 8 to 12 weeks or more. Rest cool and dark, and build the time into your production schedule.
Can I use SDA 40-B in hand sanitizer?
Yes, within the rules. FDA's OTC topical-antiseptic monograph sets ethanol at a 60 to 95% v/v final concentration, denatured per TTB rules in 27 CFR Part 20, which is exactly what 40-B is. The COVID-era temporary flexibilities were withdrawn at the end of 2021, so spec against the current monograph, and remember an OTC drug carries registration and labeling obligations a cosmetic doesn't.
Do the denaturants in 40-B affect my fragrance or skin feel?
Effectively no, which is the whole point of choosing it. The denatonium benzoate works at around 0.0006%, far too little to contribute odor or feel, and the tert-butyl alcohol is a minor fraction. That near-inert load is why the solvent disappears into a finished product and why maceration is trustworthy: what you smell at the end is your composition, not the carrier.