Reading a Preservative Blend TDS to Split the Percentages

You bought a preservative blend with a friendly trade name, the supplier's technical data sheet lists three or four INCI names under "composition," and now you need to know what percentage of each one actually ends up in your finished lotion. This trips up more makers than almost any other step in building a CNF, because the math looks simple and the paperwork usually isn't.

Why you can't just copy the blend percentage

Say your TDS lists a blend as Phenoxyethanol, Ethylhexylglycerin, and the supplier recommends using it at 1% in the finished product. The TDS composition section might show something like Phenoxyethanol at 90% and Ethylhexylglycerin at 10% of the blend itself. Those numbers describe the blend, not your product. To find each component's real concentration in your finished cosmetic, you multiply the component percentage by your use level.

• Phenoxyethanol: 90% of blend times 1% use level = 0.9% in the finished product
• Ethylhexylglycerin: 10% of blend times 1% use level = 0.1% in the finished product

That 0.9% figure is what actually matters when you're checking Phenoxyethanol against any restriction, and it's what belongs on your CNF as the individual ingredient's concentration or concentration range, not the blend's trade name.

Where the composition table hides

Technical data sheets vary wildly in layout. Some suppliers put the breakdown right on the front page under "INCI composition." Others bury it in a section labeled "regulatory" or "declaration," sometimes several pages in, sometimes only in a separate document you have to request. A few blends, frustratingly, only disclose components above a certain threshold, which means a minor ingredient at 1 or 2% of the blend might not be listed at all unless you ask the supplier directly for the full breakdown.

If your supplier's TDS gives a range instead of a fixed number, for example "Phenoxyethanol 85 to 95%," carry that range through the same multiplication and report a range on your filing rather than picking an arbitrary midpoint. Health Canada's CNF is built to accept concentration ranges, so there's no need to force a false precision that the supplier itself didn't provide.

A worked example with a second blend

Here's a slightly messier one, a common broad-spectrum blend at 0.8% use level:

Component (INCI)	% of blend	Use level	Concentration in finished product
Phenoxyethanol	80%	0.8%	0.64%
Caprylyl Glycol	15%	0.8%	0.12%
Sorbic Acid	5%	0.8%	0.04%

Each row gets checked individually against the Hotlist, not the blend as a whole, since the Hotlist restricts named substances, not commercial preservative systems. This is also why swapping preservative suppliers mid-production isn't a cosmetic change on paper, it changes your CNF because the individual component concentrations shift even if the "1% of blend X" line in your formula sheet stays the same.

Common mistakes worth watching for

• Reporting the trade name instead of the components. Trade names never appear on a filing. Every ingredient has to resolve to its INCI name.
• Forgetting a diluent or carrier. Some blends are suspended in a solvent like Propanediol or Aqua, and that carrier also needs its own line since it's technically part of what you're adding to the batch.
• Using the supplier's suggested use level instead of your actual one. If you're using the blend at 0.6% because that's what stabilized your specific formula, calculate from 0.6%, not from the supplier's default recommendation.
• Assuming a "self-preserving" claim means zero preservative. Some blends marketed as natural alternatives still contain declarable actives at meaningful concentrations, they just don't sound like classic preservatives.

Keep the paper trail

Save the TDS PDF for every blend you use, and note the version or lot date on it. Suppliers do quietly update blend ratios over time, and if you're ever asked to substantiate a CNF entry, having the exact TDS you calculated from is far more useful than a memory of what the label said.

This kind of decomposition is exactly the tedious-but-important step Cosmetic Comply automates. Feed it your formula with the blend's trade name and use level, and it expands the components, carries the percentages through, and screens each one against the Hotlist with a confidence score before a human reviewer signs off, so you're not doing the multiplication by hand on every batch.