Natural origin percentages on nail polish, explained

Up to 84 percent bio-sourced. Up to 90 percent of natural origin. A minimum of 74 percent natural origin based ingredients. Three nail polish brands, three numbers, and the same question from the reader: what is being counted, and by whom.

The answer is a calculation method called ISO 16128, a bottle that is mostly solvent, and a choice of where that solvent comes from. The method, the arithmetic, the brand claims and a checklist for reading them, with the sources behind each number.

What does natural origin mean under ISO 16128?

ISO 16128 is an international guideline that gives technical definitions for natural and organic cosmetic ingredients and a method for calculating how much of a product they make up. Part 1 (2016) defines the ingredient categories; Part 2 (2017) sets the criteria for ingredients and products (ISO 16128-2:2017). It is a guideline, not a certification: the standard does not certify a product and does not validate a marketing claim, it provides a technical basis for calculation (Alpol Cosmétique).

A natural ingredient is a material from plant, mineral, animal or microbial sources that has been processed only physically, by extraction, filtration, drying and the like. A derived natural ingredient is a natural material that has been chemically or biologically transformed. Each ingredient is given a natural origin index between 0 and 1, and an ingredient counts as of natural origin when its index is above 0.5 (Alpol Cosmétique).

The product figure is the sum of each ingredient's weight fraction multiplied by its index (Teravella). ISO 16128 sets no threshold for calling a product natural. National advertising bodies sometimes do: the French ARPP asks for at least 95 percent natural ingredients before a cosmetic is described as natural (Alpol Cosmétique).

Why does the solvent decide the number?

Nail polish is roughly 70 percent solvent by weight, mainly ethyl acetate and butyl acetate, with nitrocellulose as the film former, plus resins, plasticisers and pigments (Earth911; Personal Care Magazine). Whoever decides where the solvent comes from decides most of the natural origin figure.

Ethyl acetate is made from ethanol and acetic acid. Both can come from petroleum or from the fermentation of sugar cane, sugar beet or corn. The molecule is identical either way, but under ISO 16128 the fermented route counts as derived natural and the petroleum route does not. Inglot states that its natural origin polish uses ethyl and butyl acetate produced from sugar beet and sugar cane, nitrocellulose extracted from cotton, and plasticisers based on corn, grain and sugar beet, for a minimum of 74 percent natural origin based ingredients (Inglot).

What do the brands claim, and in which words?

Manucurist states that its Green Flash gel is made from 84 percent bio-sourced ingredients (Manucurist). Kure Bazaar states ingredients up to 90 percent of natural origin, formulated with corn, cotton and sunflower oil (MonCornerB). Inglot states a minimum of 74 percent (Inglot). Sally Hansen's Good. Kind. Pure. line is described as up to 77 percent naturally derived (Sally Hansen).

The words differ and they are not interchangeable. Natural origin is the ISO 16128 term and implies its calculation. Bio-sourced and plant-based describe where the carbon came from and say nothing about the processing. Naturally derived is a marketing phrase with no fixed method. A brand that names its method, and says whether the figure is per shade or for the line, has answered the question the number raises.

Up to and minimum are doing different work. Pigment loads vary by shade, so a range's figure moves with the colour: a sheer with little pigment scores higher than an opaque red. Up to reports the best shade; minimum reports the worst.

Is natural origin the same as natural, safe or non-toxic?

Natural origin describes where a raw material came from before it was processed. It says nothing about how a molecule behaves on the nail or in the air. Ethyl acetate from sugar cane is ethyl acetate: it has the same pear-drop smell, boils at 77 °C and is as flammable as the petrochemical version (Wikipedia). The polish dries in the same time and must be stored and disposed of in the same way.

Safety in the EU is assessed the same way for every cosmetic. Regulation (EC) 1223/2009 requires a safety assessment for the product as a whole and restricts or bans specific ingredients regardless of their origin; toluene, for instance, is limited to 25 percent in nail products whatever its source (Annex III, entry 185). The natural origin figure is separate from that system. It is a sustainability claim about feedstock, and it is fair to read it as one.

ISO 16128 also states what it does not cover: product communication, human or environmental safety, fair trade, packaging and regulatory requirements (Teravella). A high figure is a real achievement in formulation. It is a different achievement from a short free-from list or a vegan pigment set.

Why the last 10 to 30 percent is hard to replace

The solvent is the easy part, because bio-based acetates are available at scale. The remainder is the chemistry that makes a polish wear. Nitrocellulose is cotton or wood cellulose treated with nitric acid; the cellulose is natural, the nitro groups are not, so its index is a fraction. Adhesion resins that bond the film to the nail are mostly synthetic. Plasticisers can be swapped for citrate esters made from fermented citric acid, which is why many natural origin polishes list acetyl tributyl citrate.

Pigments are the hardest. Titanium dioxide, iron oxides and mica are minerals and count as natural. The bright synthetic lakes that give a clear red or a violet do not. That is why an opaque jewel-tone crème will always score a little lower than a milky sheer from the same brand, and why a 100 percent figure is not on any label.

How to read a natural origin claim: a five-point check

You will need: the product page or box, the ingredient list, and two minutes.

1. Find the method. A claim that cites ISO 16128 has a defined calculation behind it. A claim with no method is a phrase.
2. Check for water. Water has an index of 1 under ISO 16128 and inflates the figure in creams (Alpol Cosmétique). Solvent polish contains no water, so this point does not affect a polish figure; a water-based polish is a different case.
3. Read up to against minimum. Up to is the best shade in the range; minimum is the worst.
4. Look for the source of the solvent. Sugar cane, sugar beet or corn named on the page is the substance of the claim.
5. Separate the claims. Natural origin, vegan, free-from counts and EU compliance are four different facts. A polish can have all four, or one.

A percentage read this way is useful. It tells you that a brand has chosen fermented solvents over petrochemical ones and a citrate plasticiser over a phosphate, and it tells you roughly how far the swap has gone. That is worth knowing, and it is all the number knows.