Breaking Down a Broad-Spectrum Preservative Blend by Percent

You bought a preservative blend, added it at 1%, and now you're staring at a CNF form asking for INCI names and concentrations one at a time. The blend itself isn't an INCI entry. It's a mixture, usually two to four preservative actives plus maybe a solvent, and Health Canada wants each of those broken out with its own percentage.

This trips people up constantly, so let's do the actual arithmetic with a realistic example.

Why the blend can't be listed as one line

Broad-spectrum preservative blends are popular precisely because they combine actives that cover different microbial gaps, bacteria, yeast, mold, at concentrations lower than any single active would need alone. A typical blend might list something like phenoxyethanol, caprylyl glycol, and a small amount of a third stabilizing component on its technical data sheet. Each of those has its own CAS number and, potentially, its own entry or limit on the Cosmetic Ingredient Hotlist. Phenoxyethanol in particular carries a restriction in some markets, so Health Canada needs to see it standing alone, not hidden inside a trade name.

Trade names never go on the filing. That's a hard rule. Whatever the bottle says, you map it back to INCI names before it touches the CNF.

The math, step by step

Say your supplier's data sheet says the blend is:

• 70% Phenoxyethanol
• 20% Caprylyl Glycol
• 10% Water (or another carrier, sometimes listed as "balance")

And you're using that blend at 1% in your finished lotion.

To get the real concentration of each component in your product, multiply the component's share of the blend by your use level:

Component (INCI)	Share of blend	Use level of blend	Real concentration in product
Phenoxyethanol	70%	1%	0.70%
Caprylyl Glycol	20%	1%	0.20%
Water/Aqua	10%	1%	0.10%

The math is just component percent times total use level, divided by 100 if you're working in whole numbers rather than decimals. A 70% component at a 1% use level becomes 0.7% of the finished product. That's the number that goes on the CNF, not the 1% blend figure and not the 70% blend-internal figure.

Where people get it wrong

The most common mistake is filing the blend's use level (1%) against the blend's trade name, which Health Canada can't process because it isn't an ingredient. The second most common mistake is filing the internal blend percentage (70%) as if that were the finished-product concentration. Neither is right. You need the multiplied-through number.

A close third mistake: forgetting the water or carrier line entirely. Some filers assume diluents don't need to be disclosed because they're "just water." Aqua still gets listed, it's a completely normal INCI entry, you just don't want to skip it and end up with percentages on your ingredient list that don't add up to 100% across the whole formula.

What if the data sheet gives a range instead of a fixed split

Some suppliers write "60 to 75% Phenoxyethanol" rather than a single number. When that happens, you have two reasonable options: use the midpoint for your calculation and note it, or contact the supplier for the exact batch ratio if your formulation is sensitive to it (this matters more for things sitting close to a hotlist limit). For a preservative well under any restriction ceiling, the midpoint is usually fine and keeps your paperwork consistent.

Don't forget the Hotlist check itself

Once you've got your real per-ingredient percentages, check each one against the Cosmetic Ingredient Hotlist, not the blend as a whole. Phenoxyethanol has a known restriction level in Canada, and if your finished-product math puts you close to it, you want to know before you file, not after a CN number gets flagged for review. Caprylyl glycol is generally less restricted but still gets its own line and its own check.

If you're also formulating for the EU or planning to eventually list in the US, keep in mind this same blend-splitting exercise applies there too, just against different restriction lists (EU Annex III/V equivalents, or FDA's own list once MoCRA substantiation is in play). The arithmetic doesn't change, only the reference list does.

This is exactly the kind of repetitive, error-prone step that's easy to fumble by hand across a dozen SKUs. Cosmetic Comply expands supplier blends automatically and carries the percentages through to each INCI component with its CAS number, so the multiplication and the Hotlist screening happen together instead of as two separate manual passes. It's built for the notification step in Canada right now, with the US, EU, and Australia coming.

Whatever tool or spreadsheet you use, the underlying rule stays simple: every component gets its own line, its own real percentage, and its own check. The blend name is just packaging.