Reading Section 3 When Your Ingredient Is a Mixture

I had a maker send me a screenshot last month, an SDS Section 3 with five rows in it for what she thought was a single ingredient, a "natural preservative" she'd bought from a small supplier. She wanted to know which row to put on her filing. The answer is all of them, and here's how to think it through.

Substance versus mixture, and why the SDS tells you which

Section 3 of a safety data sheet is titled either "Substance" or "Mixture," and that heading is your first clue. If it says Substance, you're looking at one chemical entity, one CAS number, one row, done. If it says Mixture, the supplier is telling you upfront that what you bought is a combination, and the table underneath will list each hazardous or notable component separately.

This matters because a lot of "natural" or "specialty" ingredients marketed under a single brand name are, chemically, small formulated blends. Preservative systems are the classic example, but you'll see it with some botanical complexes, some emulsifying waxes, and plenty of fragrance or active blends too.

What a mixture-type Section 3 actually looks like

A typical mixture entry might read something like this, simplified:

Component	CAS number	Concentration range
Component A	(listed)	15 to 30%
Component B	(listed)	5 to 10%
Component C	no CAS available	balance

Notice the third row. Some botanical extracts genuinely have no CAS number, that's not an error or an omission on the supplier's part, it's just how the substance is classified. You'll still list it by INCI name, just without a CAS reference.

Why you can't just write down the blend's trade name

Health Canada's CNF wants INCI names with concentrations, not trade names, and a mixture-type SDS is precisely the document that tells you what's actually inside the bottle. If you file the trade name alone, you're not meeting the requirement, and if any single component in that blend happens to sit on the Cosmetic Ingredient Hotlist, a reviewer has no way to catch that from a brand name alone.

So the job is: take each row from that Section 3 table, confirm its INCI name (sometimes the SDS uses an IUPAC or trade chemical name instead of INCI, so double check against the technical data sheet or ask the supplier), and carry the concentration range through your own math.

Doing the math when it's a mixture within a mixture

This gets one layer deeper than a simple preservative blend, because you're not just multiplying by your use level, you're multiplying by both your use level and the mixture's own ratio. If you use the blend at 2% in your formula, and Component A sits between 15 and 30% inside the blend, its real concentration in your finished product ranges from 0.3% to 0.6%. Use the midpoint (22.5%) for a working number, 0.45% in this example, unless the ingredient is close enough to a restriction that you need the supplier's exact batch figure.

When concentration ranges are wide

Wide ranges (say, 10 to 40%) usually mean the supplier is being conservative about disclosing an exact recipe, not that the batch genuinely varies that much. If the component in question isn't on any restricted list, this is rarely worth chasing further. If it is restricted, or close to a limit, it's worth a direct email to the supplier's regulatory contact asking for the number used in your specific lot or batch code.

A habit worth building

Whenever a new ingredient comes in, glance at Section 3 before you do anything else with the document. That one heading, Substance or Mixture, tells you whether you're about to do a one-line lookup or a multi-row breakdown. Skipping that check is how single ingredients get filed as if they were simple, when really they're three or four regulated components wearing one trade name.

This is one of the more tedious parts of putting together an accurate ingredient list, matching every row in a mixture's SDS to its INCI name and CAS number, then carrying the math through correctly. Cosmetic Comply does this expansion automatically when you upload your formula and supplier documents, screening each resulting component against the market's restricted list rather than just the blend as a whole. It won't replace reading the SDS yourself, but it does cut out a lot of the manual cross-referencing.

Keep the original SDS on file regardless of what tool you use. If a formula ever gets questioned, that document is your paper trail for where every percentage came from.