Identifying What Leaf You Actually Have: Karat Stamps, Tarnish, and Why Dutch Metal Isn't on the Scale at All

Sooner or later, most gilders end up holding a sheet or a book of leaf with no clear idea what it actually is — inherited materials, a vaguely worded listing, or an old restoration where nobody wrote down what was used. Working it out isn't guesswork if you know what to check, and the single most common source of confusion has a precise, fixable answer: karat is a gold-purity measurement, full stop, and several materials that get called “gold” in casual conversation aren't on that scale at all.

Start with the definition, not the label

Karat counts parts of gold out of 24 by mass: divide the karat by 24 and multiply by 100 for the exact gold percentage. That formula is exact and checkable for any number up to 24 — a 20-karat alloy is 20/24, or 83.3% gold; a 14-karat alloy is 14/24, or 58.3% gold. There's no such thing as a 26-karat or a 30-karat anything, because the scale is capped at 24 by definition; any listing claiming a karat above 24 has made an error or is describing something other than gold purity.

Applied to the varieties gilders actually encounter, the scale runs cleanly: 24k genuine leaf is 100% gold, 23k is 95.8%, 22k is 91.7%, 18k lemon gold is exactly 75%, 16k green gold is 66.7%, and 12k white gold (sometimes sold as “moon gold”) sits at an even 50%. Every one of those numbers comes directly from the karat-over-24 formula — nothing about them is a marketing choice or a rounded approximation.

The materials with zero karat, not low karat

Here's the distinction that trips up almost everyone new to the material: palladium leaf, silver leaf, and composition leaf (also called Dutch metal or schlag) all show 0% gold content, but they are not “very low karat gold.” They simply aren't gold alloys at all, and karat as a measurement doesn't apply to them in any sense — the same way it would be meaningless to describe a steel object as having a karat rating. Composition leaf is a copper-zinc alloy, essentially brass, made to resemble gold leaf visually but containing none of it. Silver leaf is pure silver, a genuine precious metal but a different one entirely. Palladium leaf is a platinum-group metal, again genuine and precious, again not gold. If a listing, a label, or a previous owner's notes describe any of these with a karat number, that number is either a mistake or is being used loosely to mean something like “how gold-like it looks,” not an actual purity measurement — and it's worth mentally discounting it either way.

This matters beyond pedantry. Treating composition leaf as if it were simply a very low-karat gold leads to a real, costly misunderstanding: the expectation that it will behave like gold and resist tarnish. It won't. Genuine gold, at any karat gilders use down through 12k, resists oxidation because there's still enough actual gold in the alloy to dominate its chemistry. Composition leaf has none, so it tarnishes like the brass it is, on a timeline of months rather than centuries.

Physical tells you can check yourself

A handful of practical checks help sort out what you're holding without any special equipment. Thickness and stiffness are the first: genuine loose leaf, especially at standard thickness, feels almost fluid and settles into detail readily, while composition leaf is conventionally beaten thicker and feels noticeably stiffer and more opaque in the hand. Light transmission is a second, more decisive check for loose leaf specifically — hold a genuine sheet up to a strong light source and you can often see a faint greenish glow passing straight through it, a direct consequence of how thin genuine leaf is beaten; composition leaf, being both thicker and a different metal, won't do this.

Tarnish over time is the most decisive check of all, if you have the patience for it. Set a small, clean sample of unsealed leaf aside and check it after a few weeks to a few months in normal room conditions. Genuine gold, any karat, will look essentially unchanged. Composition leaf will visibly dull, and often develop a greenish or brownish cast as its copper content oxidizes. Silver leaf sits in between: it will tarnish, but far more slowly and evenly than composition leaf's brass alloy, and it's still a genuine precious metal rather than an imitation, which distinguishes it clearly from composition once you know to look at the pattern of tarnish rather than just its presence.

Price is a blunt but honest signal

Genuine and composition leaf sit in such different price tiers per book that price alone is often the fastest sanity check available, particularly when buying rather than identifying something already on hand. A book of “gold leaf” priced at a small fraction of what genuine leaf typically costs is almost certainly composition leaf regardless of how its listing is worded, simply because the raw material costs involved make genuine leaf's price floor much higher. This isn't a substitute for reading a listing carefully, but it's a useful gut check before relying on marketing language alone.

A full identification checklist, side by side

It helps to see every common variety laid out together rather than one at a time. Genuine leaf runs from 24k (100% gold, a deep reddish yellow) down through 23k (95.8%, rich yellow), 22k (91.7%, warm yellow), 18k lemon gold (75%, pale lemon yellow), and 16k green gold (66.7%, a subtle green cast), to 12k white gold or moon gold (an even 50% gold-silver split, pale and cool but not a true white). Below and beside that scale, entirely separately, sit palladium leaf (a bright, genuinely tarnish-resistant cool white with zero gold content), silver leaf (bright white, a genuine precious metal that tarnishes slowly), and composition leaf (brassy yellow, zero gold content, tarnishes quickly). Notice the shape of that list: everything from 24k down to 12k is a real point on one continuous gold-purity scale, and everything below that line — palladium, silver, composition — is a different material family entirely, not a continuation of the same scale at a lower number.

What a supplier's label should actually tell you

A properly labeled product gives you three pieces of information: a karat number (only meaningful for genuine gold-alloy leaf), a color or variety name, and an explicit word like “genuine” versus “composition,” “imitation,” or “Dutch metal.” A label missing that third piece of information, or one that pairs a karat-sounding number with a price and description that otherwise reads like composition leaf, is worth a direct question to the seller before you buy. This is especially worth doing for anything bought secondhand, at an estate sale, or from a seller who may not have originally purchased the material themselves and is simply passing along whatever description came with it.

Tests to skip

It's worth explicitly ruling a few things out, too. Acid or scratch tests used to verify solid gold jewelry rely on there being enough metal present to test meaningfully, and they involve strong acids that have no business anywhere near a workspace covered in loose, static-sensitive leaf — leave those tests, and the acids involved, to a qualified jeweler or assayer working with solid metal, not leaf. For leaf specifically, the non-destructive checks above — feel, light transmission, tarnish over time, and an honest look at price — will get you a confident answer without introducing a hazardous chemical into a gilding workspace at all.

Restoration work: when it actually matters

Identification stops being a curiosity and becomes essential the moment you're restoring or touching up an existing piece and need to match what's already there. Regilding a section in the wrong material — composition leaf next to decades-old genuine gold, or a mismatched karat and alloy next to an existing color — will read as an obvious patch under close inspection or over time, once the new material's tarnish behavior or color drift diverges from the original. Testing a small, inconspicuous sample area and giving it time (weeks, ideally, not minutes) to reveal whether it tarnishes is worth the delay on anything where matching an existing finish actually matters, and it's far cheaper than redoing a visible repair a second time.

The Gold Leaf Karat & Color Guide lists every common genuine karat alongside palladium, silver, and composition leaf with their gold percentage, color, and typical use side by side, which is a fast way to cross-check a specific label or listing against the real numbers. For the color science behind why karat and color are two separate questions, see understanding gold leaf karats and color, and for the cost and durability consequences of the genuine-versus-composition choice, see genuine vs. composition leaf.